International Conference on

12th

12 th

GGAS AS G MS IIN N M ARINE MARINE SSEDIMENTS EDIMENTS 2014 Taiwan

Program Proceeding September 1st-6th, 2014 Taipei, Taiwan

12th International Conference on Gas in Marine Sediments GIMS 12 Taipei, Taiwan September 1-6, 2014

Organized by Department of Geosciences, National Taiwan University (NTU)

12th International Conference on Gas in Marine Sediments Taipei, Taiwan, September 1-6, 2014 Organized by Department of Geosciences, National Taiwan University (NTU) Co-organized by: Institute of Earth Sciences, Academia Sinica Taiwan Ocean Research Institute, NARL Department of Earth Sciences, National Central University (NCU) Exploration & Development Research Institute, Chinese Petroleum Corporation (CPC) Institute of Marine Geology and Chemistry, National Sun Yat-sen University (NSYSU) Department of Life Sciences, National Chung Hsing University (NCHU) Institute of Oceanography, National Taiwan University (NTU) Institute of Applied Marine Physics and Undersea Technology, National Sun Yat-sen University (NSYSU) Institute of Applied Geosciences, National Taiwan Ocean University (NTOU) Central Geological Survey, MOEA Department of Earth Science, National Cheng Kung University (NCKU) Geological Society located in Taipei Chinese Geoscience Union

Sponsored by Ministry of Science and Technology International Committee: Aloisi, G. (France) Boetius, A. (Germany) Bohrmann, G. (Germany) Capozzi, R. (Italy) De Batist, M. (Belgium)

Leifer, I. (USA) MacDonald, I. (USA) Matveeva, T. (Russia) Minami, H.(Japan) Obzhirov, A. (Russia)

Dimitrov, L. (Bulgaria) Garcia-Gil, S. (Spain) Grachev, M. (Russia) Hovland, M.(Norway) Jørgensen, B.B.(Denmark) Judd, A. (Great Britain)

Orange, D. (Indonesia) Pierre, C. (France) Pimenov, N. (Russia) Suess, E. (Germany) Woodside, J. (The Netherlands) Yang, T. F. (Taiwan)

Organizer: Dr. Tsanyao Frank Yang Department of Geosciences National Taiwan University No. 1, Sec. 4, Roosevelt Road Taipei 106, TAIWAN Tel: +886-2-3366-5874 Fax: +886-2-2363-6095 E-mail: [email protected]

Local Organizing Committee: Li-Jen Chen (Department of Chemical Engineering, NTU) Wu-Cheng Chi (Institute of Earth Sciences, Academia Sinica) Gwo-Ching Gong (Taiwan Ocean Research Institute, NARL) Shu-Kun Hsu (Department of Earth Sciences, NCU) Hsing-Tai Hu (Exploration & Development Research Institute, CPC) Chin-Chang Hung (Institute of Marine Geology and Chemistry, NSYSU) Mei-Chin Lai (Department of Life Sciences, NCHU) Saulwood Lin (Institute of Oceanography, NTU) Chau-Chang Wang (Institute of Applied Marine Physics and Undersea Technology, NSYSU) Tan-Kin Wang (Institute of Applied Geosciences, NTOU) Yunshuen Wang (Central Geological Survey, MOEA) Tsanyao Frank Yang (Department of Geosciences, NTU) Chen-Feng You (Department of Earth Science, NCKU)

Secretariat: Yuchun Huang Chia-Ling Cheng Min-Lin Shen Nai-Chen Chen Tzu-Tsen Shen

Chun-Ming Chiu Shih-Jung Lin Vivek Walia Monika Walia Arvind Kumar

Tsung-Han Yang You-Chen Cheng Jin-Lun Chuang Li-Hsin Kao Chun-Wei Lai

Hsiao-Fen Lee Yi-Jyun Chen Ching-Chou Fu Hsuan-Wen Chen Ai-Ti Chen Chien-Jen Chen

Hsin-Yi Wen Yao-Rui Wang Cheng-Yin Wu Kuo-Wei Wu Hsuan-Cheng Wei Hiao-Hien Chang

Tzu-Yu Lin Nga-Chi Cheung Wuh-Terng Lim Yueh-Ting Lin Kai-Wen Tang Jui-Fen Tsai

Edited by Yuchun Huang and Tsanyao Frank Yang

General Information Schedule for 12th GIMS Sun.

Mon.

Tues.

Wed.

Thur.

Fri.

Sat.

8/31

9/1

9/2

9/3

9/4

9/5

9/6

a.m.

Program

Program

Program

Program

p.m.

Program

Program

City Tour

Program

Field

Field

Excursion

Excursion

18:00

Welcome

Banquet

Party

Party

Ice Breaker

20:00

Conference venue The International Conference Hall of Law College, NTU. (Intersection of Fuxing S. Rd and Xinhai Rd.) There will be a staff waiting at the front desk of Yo Xing Regency (near MRT Guting Station) and Li Yuan Hotel (near MRT Taipower Building Station) at 08:00 on September 1st and guide you to the conference venue.

NTU Campus

MRT Gongguan Station

GIMS12 Venue

Dept. of Geosciences

Special issue as conference proceedings We will contact with Springer publisher for potential publication of a conference volume in the journal Geo-Marine Letters. Detailed requirements for preparation of the manuscripts will be given in future information.

Guideline for presentation Oral Presentation Except for the keynote address, the presentation time for each speaker is 20 minutes (both including 5 min discussion) for oral sessions. There is only one screen in the conference hall. No overhead projector will be provided. The speakers need to prepare their slides in the format of Microsoft PowerPoint file. Poster Presentation

scheduled poster sessions before moving to the poster place for further discussion. In addition to the poster, therefore, the authors need to prepare 3-5 slides in the format of Microsoft PowerPoint file too.

90 cm

120 cm

The frame size for poster display is 120cm (height) x 90cm (width) (Standard size of A0). All presenting authors of poster sessions are requested to present their work briefly for 2 minutes at the beginning of

All posters can be posted up from September 1st to September 4th. Registration The registration and information desk will open from 08:30 to 17:00 during the conference time (September 1st to 4th) at the conference venue. Free Wi-Fi NTU campus Wi-Fi account number and password will be provided at registration and information desk. Parking preference The parking tickets of NTU campus will be available with preferential price (50% discount, NT$30/30mins→NT$15/30mins) at registration and information desk. Ice Breaker The ice breaker of GIMS12 will take place at Department of Geosciences in NTU campus starting from 18:00 of Sunday, 31 August, 2014. Registration desk will open there from 17:00 to 20:30. There will be a staff waiting at the front desk of Yo Xing Regency (near MRT Guting Station) and Li Yuan Hotel (near MRT Taipower Building Station) at 17:00 and guide you to the place of Ice Breaker. Lunch During the conference, lunch boxes will be provided for all participants (from September 1st to 4th).

Welcome Party The welcome party of GIMS12 for all participants will be held in the evening of September 1st, 2014, at la marée restaurant. There will be a staff waiting at the front desk of Yo Xing Regency (near MRT Guting Station) and Li Yuan Hotel (near MRT Taipower Building Station) at 18:00 and guide you to the restaurant. Banquet All participants are invited to join the GIMS12 Banquet held in the evening of September 3rd, 2014, at la marée restaurant. Cultural performances will be arranged. City Tour The organizing committee is arranging a half-day city tour for all participants in the afternoon of 3 September to visit some must-go spots in Taipei city. We will visit Confucius Temple, Baoan Temple and Chiang Kai-shek Memorial Hall and, Taipei 101 if we can have enough time. The bus will leave at 13:00 from the gate of campus near the conference venue. It will stop by the hotel Yo Xing Regency (near MRT Guting Station) and Li Yuan Hotel (near MRT Taipower Building Station) on the way back, and stop at the main gate of NTU campus around 17:00pm. Please do register at the information desk before noon of September 1st, if you are interested in joining the city tour. Weather The average temperature in September in Taiwan is 23-32 degree Celsius. The average relative humidity is 70% - 80%. Please do sun protection when you are outside the building. It is quite often to have thunderstorm and rains in the afternoon in summer days. During this time, the invasion of typhoons is possible. A lightweight umbrella by your side is recommended. Please check the local weather at the website of Taiwan Central Weather Bureau. (http://www.cwb.gov.tw/eng/index.htm) AC power socket There are 2 kinds of AC power socket in Taiwan with voltage of 110V. Field Trip Following the 4-day scientific sessions at NTU campus, a two-day field trip is organized to visit 921 earthquake Museum and Chelungpu Fault Preservation Park in central Taiwan and mud volcanoes/seepages along active fault zones in southwestern Taiwan. For prevention of mosquitos and other pests, we will suggest wearing long pants and sleeved blouse. Sun protection is also important in the field.

12th International Conference on Gas in Marine Sediments GIMS 12 Program Taipei, Taiwan September 1-6, 2014

Organized by Department of Geosciences, National Taiwan University (NTU)

I

12th International Conference on Gas in Marine Sediments Taipei, Taiwan, September 1-6, 2014 August 31, 2014 (Sunday)

17:30-20:30 Registration 18:00-20:30 Ice Breaker

III

12th International Conference on Gas in Marine Sediments Taipei, Taiwan, September 1-6, 2014 September 1, 2014 (Monday)

08:30-09:00

Registration

09:00-09:30

Opening

Oral Session I Convener: Tsanyao Frank Yang 09:30-10:10: GIMS12A087

Keynote Speech

Miriam Kastner Gas Hydrates (Clathrates) in Marine Sediments - Key Questions 10:10-10:40

Group Photo and Break

Oral Session II Convener: Marc De Batist 10:40-11:20: GIMS12A088

Keynote Speech

Christian Berndt Gas Hydrates in the Climate System 11:20-11:40: GIMS12A063 Ian R MacDonald, Oscar Garcia-Pineda, Mauricio Silva, Samira Daneshgar-Asl, Caroline Johansen, Chris Reddy and William Shedd Post-Accident Discharge Forensics at the Deepwater Horizon Site, Gulf of Mexico 11:40-12:00: GIMS12A085 Tsanyao Frank Yang, Nai-Chen Chen, Chin-Yi Hu, Pei-Chuan Chuang, Hsuan-Wen Chen, Saulwood Lin, San-Hsiung Chung, Yunshuen Wang and Po-Chun Chen Methane Flux in Gas Hydrate Potential Areas off SW Taiwan 12:00-13:30

Lunch IV

2014 Sep. 1st

Oral Session III Convener: Martin Hovland 13:30-13:50: GIMS12A003 Heiko Sahling, Miriam Römer, Thomas Pape, Christian dos Santos Fereirra, Gerhard Bohrmann and Benoît Bergés Quantification of Gas Emissions at the Continental Margin West of Svalbard 13:50-14:10: GIMS12A007 Timo Zander, Ingo Klaucke, Jörg Bialas, Christian Berndt, Dirk Kläschen and Cord Papenberg Are Cold Seep Locations Controlled by Topography or Gas Hydrate Distribution A View from the Kerch Seep Plumbing System in the Black Sea 14:10-14:30: GIMS12A025 Shakirov Renat, Nguyen Nhu Trung, Duong Quoc Hung, Syrbu Nadezhda, Le Duc Anh, Mal’tseva Elena, Telegin Iurii, Polonik Nikita and Obzhirov Anatoly The Anomalies of Natural Gases in the Sediments and Seawater in the Gulf of Tonkin (BacBo, South-China Sea), Vietnam 14:30-14:50: GIMS12A005 Ingo Klaucke, Saulwood Lin, Christian Berndt and SO227 Scientific Party Surface Expression of Cold Seeps on the Continental Margin offshore SW Taiwan 14:50-15:10: GIMS12A006 Wen J Whan, K. M. Tsai, Hsiupo Yeh, Jiann-Lin Chen and Jeng-Yu Lin Real Time Sea Bed Shallow Sounding for Resistive or Conductive Target Layer 15:10-15:30: GIMS12A092 Y. Sano, H. Wen, T. Kagoshima, N. Takahata, Y. Tomonaga, A. Ishida, K. Tanaka and K. Shirai, J. Ishibashi,H. Yokose, U. Tsunogai and T.F. Yang Helium and carbon flux from shallow submarine hydrothermal system in the Tokara Islands, Southwestern Japan 15:30-15:50

Break

V

15:50-16:30 2014 Sep. 1st

Poster Session I Convener: Wu-Cheng Chi GIMS12A002: Win-Bin Cheng, Shiao-Shan Lin, T. Y. Shih, Tan-Kin Wang, Char-Shine Liu, Song-Chuen Chen and Yunshuen Wang Imaging Three-Dimensional Seismic Velocities for Hydrate-Bearing Sediments Near YuanAn Ridge, off Southwest Taiwan GIMS12A004: Sheng-Chung Chen, Mei-Chin Lai and Saulwood Lin Analyses of Microbial Diversities and Functions in Potential Gas Hydrate Bearing Area at Offshore Southwestern Taiwan by Metagenomic Approach GIMS12A009: In-Tian Lin, Ching-Tse Chang, Jun-Chin Shen and Tsanyao Frank Yang The Genetic Type and Accumulation Characteristics of Biogas in the Guan Tian Area of South-Western Taiwan GIMS12A010: Dong Feng and Duofu Chen Fluid Sources, Intensities, and Biogeochemical Processes of an Active Cold Seep from the Northern South China Sea Initial Results of Manned Submersible Jiaolong GIMS12A011: Hongxiang Guan, Nengyou Wu, Dong Feng and Duofu Chen Molecular Fossils Reveal Biogeochemical Process at an Active Methane Seep from the Northern South China Sea GIMS12A012: Sandra Hurter, Stefan Bünz, Andreia Plaza-Faverola and Jürgen Mienert Time-Lapse Seismic Study of Active Gas Seepage at The Arctic Vestnesa Ridge, Southern Fram Strait GIMS12A015: Chien-Hui Yang, Tin-Yam Chan, Shinji Tsuchida, Katsunori Fujikura, Yoshihiro Fujiwara and Masaru Kawato Connectivity of the Chemosynthetic Squat Lobster Shinkaia Crosnieri (Crustacea: Decapoda: Galatheidae) Between the Cold Seep and Hydrothermal Vent Habitats in the Northwest Pacific GIMS12A016: Huai-Houh Hsu, Jia-Jyun Dong, Che-Ming Yang, Shu-Kun Hsu and WinBin Cheng Slope Analysis of a Submarine Landslide near the SW Xiaoliuqiu VI

GIMS12A017: Chia-Hsien Chao, Chih-Chien Chang, Mei-Chin Lai, Saulwood Lin and LiLian Liu Population and Reproduction of the Mussel Bathymodiolus Platifrons from Seeps in Southwestern Taiwan GIMS12A018: Qinxian Wang, Chiyue Huang and Duofu Chen Petrographic and Geochemical Characterization of Cold Seep Carbonate in the Kuohsing Area, Taiwan GIMS12A027: Daidai Wu and Nengyou Wu Geochemical Research of Gas Hydrate in the Northern South China Sea GIMS12A028: Shuhong Wang, Wen Yan, Jiaxiong He, Wei Zhang and Zhenquan Lu Biogenicsub-Biogenic Gas Resource Potential and Gas Hydrate Accumulation in the Pearl River Mouth Basin of the Northern South China Sea GIMS12A029: Song-Chuen Chen, Shu-Kun Hsu, Yunshuen Wang, San-Hsiung Chung, PoChun Chen, Ching-Hui Tsai, Hsiao-shan Lin,Char-Shine Liu, Saulwood Lin and Ho-Han Hsu Seabed Features in the Gas Hydrate Potential Area of the Yung-An and Good Weather Ridges, off Southwest Taiwan GIMS12A069: Li-Hsin Kao, Tsanyao Frank Yang, Hsin-Yi Wen, Ai-Ti Chen and HsiaoFen Lee Helium Isotopes of Fluids from Submarine Volcanoes in the South-Okinawa Trough GIMS12A076: Hsin-Yi Wen, Tsanyao Frank Yang, Li-Hsin Kao, Hsiao-Fen Lee, Yuji Sano, Naoto Takahata and Shinsuke Kawagucci Gas Geochemistry Characteristics of Hydrothermal Fluids from the Southwestern Okinawa Trough 16:30-17:20

Poster Discussion

18:30-20:30

Welcome Party

VII

2014 Sep. 1st

12th International Conference on Gas in Marine Sediments Taipei, Taiwan, September 1-6, 2014 September 2, 2014 (Tuesday)

Oral Session IV Convener: Christian Berndt 08:30-09:10: GIMS12A089

Keynote speech

Char-Shine Liu Taiwan Gas Hydrate Investigation Program: Present Status and Future Prospective 09:10-09:30: GIMS12A034 Timo Zander, Jörg Bialas, Christian Berndt, Ingo Klaucke, Dirk Klaeschen, Stephanie Koch, Cord Papenberg and MSM34 Scientific Parties Gas Hydrate Distribution in Channel-Levee Systems of the Danube Deep-sea Fan (Black Sea) Revealed by New Seismic Data. 09:30-09:50: GIMS12A026 Lisa Vielstädte, Jens Karstens, Matthias Haeckel, Mark Schmidt, Peter Linke, Susan Reimann, Volker Liebetrau, Klaus Wallmann and Daniel F. McGinnis Anthropogenic Methane Emissions from Abandoned Oil and Gas Wells in the North SeaHow much Methane is Leaking into the Ocean and finally into the Atmosphere 09:50-10:10: GIMS12A046 Chau-Chang Wang, Hsin-Hung Chen, Yuan-He Lin, Jian-Hong Chen, Chun-Cheng Huang, Chia-Min Lin, Chung-Ray Chu, Ying-Hsueh Chien and Chin-Chang Hung Development of Abyss Twisted-Pair Imaging System and Autonomous Benthic Lander for Gas Hydrate Exploration 10:10-10:30

Break

VIII

2014 Sep. 2nd

Oral Session V Convener: Anatoly Obzhirov 10:30-10:50: GIMS12A038 Saulwood Lin, Wan-Yen Cheng, Chieh-Wei Hsu and Tsanyao Frank Yang Gas Seeps BioGeoChemical Anomalies at Active and Passive Margin of the South China Sea 10:50-11:10: GIMS12A045 Boris Baranov, Dar’ya Rukavishnikov, Young Keun Jin, Vladimir Prokudin, Alexander Salomatin, Natal’ya Nikolaeva, Alexander Derkachev, Anatoliy Obzhirov, Hirotsugu Minami and Hitochi Shoji Methane Gas Flares in the Tatarskyi Strait 11:10-11:30: GIMS12A062 Nai-Chen Chen, Tsanyao Frank Yang, Yu-Chun Huang, Hsuan-Wen Chen, Lulu Chen Hong-Chun Li, Pei-Ling Wang, Chin-Chang Hung and Chau-Chang Wang Geochemistry of Gases and Fluids at “MV12” Offshore SW Taiwan 11:30-11:50: GIMS12A014 Martin Hovland and David Riggs The Bremer Canyon Ocean Animal Hotspot: - A Case of Seepage-Induced Congregation? 11:50-12:10: GIMS12A044 Ruei-Long Guo, Mmeng-Shen Huang, Yu-Shih Lin, Li-Hung Lin, Tsanyao Frank Yang, Pei-Ling Wang and Saulwood Lin Aerobic Conversion of Methane to Inorganic and Organic Carbon Pools Assessed by Stable Isotope Probing 12:10-13:30

Lunch

Oral Session VI Convener: Catherine Pierre 13:30-13:50: GIMS12A019 Anatoly Obzhirov Methane Fluxes, Gas Hydrate and Oil-Gas Deposit in the Okhotsk Sea

IX

13:50-14:10: GIMS12A052 2014 Sep. 2nd

Li-Hung Lin, Pei-Ling Wang, Tsanyao Frank Yang and Yunshuen Wang Comparative Methane Cycling and Microbial Communities in Marine and Terrestrial Mud Volcanoes 14:10-14:30: GIMS12A020 Stephanie Koch, Joerg Bialas, Matthias Haeckel, Gareth Crutchley, Cord Papenberg and Dirk Klaeschen Doming and Seepage, Development of shallow Gas Migration Pathways - Opouawe Bank, Offshore New Zealand 14:30-14:50: GIMS12A013 Akihiro Hiruta, Tsanyao Frank Yang, Yi-Jyun Chen, Hsuan-Wen Chen, Nai-Chen Chen, Tsun-Han Yang, Kuo-Yen Wei, Jyh-Jaan Huang, Sheng-Rong Song, Chih-Chieh Su, Saulwood Lin and Song-Chuen Chen Activating Mud Volcanism Indicated by 210Pb Geochronology at a Submarine Mud Volcano, Offshore Kaohsiung, Southwestern Taiwan 14:50-15:10: GIMS12A051 Hsuan-Wien Chen, Hsing-Juh Lin and Chun-Ming Yeh Trophic Structure of Megabenthic Assemblages at Seep and Surrounding Ecosystems in the South China Sea 15:10-15:30: GIMS12A093 Sutieng Ho, Patrice Imbert, Joe Cartwright and Jean-Philippe Blouet Intensity of Hydrocarbon Leakage Reflected by Vertical Successions of Methane-Related Carbonates, Pockmarks and Chimneys; A Study of Fluid Venting Structure in 3D Seismic Data, Offshore Angola 15:30-15:50

Break

15:50-16:30 Poster Session II Convener: Saulwood Lin GIMS12A001: Yuchun Huang, Tsanyao Frank Yang, Nai-Chen Chen, Ching-Yi Hu Saulwood Lin and Song-Chuen Chen Origin and Flux of Methane Gas from Submarine Mud Volcanoes in the Upper Slope off SW Taiwan X

GIMS12A064: Tsung-Han Yang, Tsanyao Frank Yang, Nai-Chen Chen, Saulwood Lin, Pei-Ling Wang and Shu-Kun Hsu Temporal Variations of Methane Flux from Submarine Mud Volcanoes off Southwest Taiwan GIMS12A021: Hongpeng Tong and Duofu Chen A Newly Discovered Cretaceous Seep Carbonates in Tibet GIMS12A022: Min Luo, Duofu Chen, Andrew W. Dale and K. Wallmann Microbial Turnover and Benthic Geochemical Flux of the Pockmark Field in Southwestern Xisha Uplift, Northern South China Sea: Insight from Reaction-Transport Model GIMS12A030: Yuncheng Cao and Duofu Chen Numerical Simulation of Gas Composition Differentiation in Marine Sediments An Application at IODP Site 1327 GIMS12A008: Yu Hu, Duofu Chen, Qianyong Liang and Hongbin Wang Pore Water Geochemistry in Shallow Sediments in the Dongsha Area of Northern South China Sea: Evidences of the Anaerobic Oxidation of Methane and its Impact on the Cycle of Redox-Sensitive Elements GIMS12A033: Akihiro Hachikubo, Hirotoshi Sakagami, Hirotsugu Minami, Satoshi Yamashita, Nobuo Takahashi, Hitoshi Shoji, Young Keun Jin, Olga Vereshchagina and Anatoly Obzhirov Gas Hydrate Characteristics Retrieved off Southeastern and Southwestern Sakhalin Island GIMS12A023: Yota Sasaki, Hirotsugu Minami, Akihiro Hachikubo, Satoshi Yamashita, Takuma Hirano, Hirotoshi Sakagami, Nobuo Takahashi, Hitoshi Shoji, Young Keun Jin Nataliya Nikolaeva, Alexander Derkachev, Anatoly Obzhirov and Boris Baranov Low Chloride Anomalies in Sediment Pore Waters off Southwest Sakhalin Island, Russia GIMS12A037: Che-Kang Chu, Yan-Ping Chen, Shiang-Tai Lin, Li-Jen Chen and Po-Chun Chen Measurements and Prediction of Methane Hydrate Equilibrium in the Presence of Ionic Liquid 1-Ethyl-3-Methylimidazolium Chloride

XI

2014 Sep. 2nd

2014 Sep. 2nd

GIMS12A053: Wei-Zhi Liao, Andrew Tien-Shun Lin, Char-Shine Liu, Jung-Nan Oung and Yunshuen Wang Geothermal Gradient and Heat Flows in the Continental Slope of the Northern South China Sea near Taiwan GIMS12A054: Wan-Yen Cheng, Jing-Yang Tseng, Saulwood Lin, Chieh-Wei Hsu, Genady V. Kalmychkov and Tatyana V. Pogodaeva Climatic Change and Records of AOM in the Lake Baikal Freshwater Environment GIMS12A055: Po-Chun Chen, Kuan-Chen Liu, San-Hsiung Chung, and Yunshuen Wang Using Ethanol Vapor as Catalyst for Decomposing Artificial Methane Hydrate GIMS2A056: Makarov Mikhail Mikhailovich, Kucher Konstantin Miroslavovich, Granin Nikolay Grigorievich, Gnatovskiy Ruslan Yurievich and Muyakshin Sergey Ivanovich Observation and Quantification of Bubble Gas Escapes in Lake Baikal with Echosounder GIMS12A057: Elodie Lebas, Theresa Roth, Christian Berndt, Marion Jegen, Anne Krabbenhoeft, Cord Papenberg, Anke Dannowski and Wu-Cheng Chi P-Wave Velocity Model above the Formosa Ridge (Southwest off Taiwan) from Combined Analysis of OBS and Multichannel Seismic Reflection Data GIMS12A074: Evan A. Solomon, Susan Hautala, H. Paul Johnson, Una K. Miller, Brendan Philip and Robert Harris Response of the Cascadia Margin Gas Hydrate Reservoir to Warming North Pacific Intermediate Water 16:30-17:20

Poster Discussion

XII

12th International Conference on Gas in Marine Sediments Taipei, Taiwan, September 1-6, 2014 September 3, 2014 (Wednesday)

Oral Session VII Convener: Hirotsugu Minami 08:30-09:10: GIMS12A090 Keynote speech Ryo Matsumoto 10 Years Shallow Gas Hydrate Exploration in Japan Sea 09:10-09:30: GIMS12A043 Alexander V. Egorov, Robert I. Nigmatulin and Alexey N. Rozhkov Field Experiments on Decomposition of Deepwater Gas Hydrates During the Lifting from the Bottom to the Surface 09:30-09:50: GIMS12A039 Dupuis Matthieu, Vendeville Bruno and Imbert Patrice Geometric Analysis of a Cluster of Mud Volcanoes and Associated Mud Chambers Description of Shallow Fluidization Zones 09:50-10:10: GIMS12A077 Patrice Imbert, Matthieu Dupuis, Viviane Casenave, Bruno Vendeville and Francis Odonne Turning Stratified Fine-Grained Sediment into Homogeneous Mud: the Role of Gas 10:10-10:30

Break

XIII

Oral Session VIII 2014 Sep. 3rd

Convener: Yunshuen Wang 10:30-10:50: GIMS12A032 Catherine Pierre and Jérôme Demange Oxygen and Sulphur Isotopic Compositions of Authigenic Gypsum from Methane Seeps of the Southwest African Continental Margin 10:50-11:10: GIMS12A024 Chuan-Chou Shen, Yi-Chi Chen, Yun-Shuen Wang, Po-Chun Chen, Horng-Sheng Mii Shih-Wei Wang, Pei-Ling Wang and Saulwood Lin Active Methane Seep Events Offshore Southwestern Taiwan Inferred from 230Th-Dated Authigenic Carbonate 11:10-11:30: GIMS12A083 Glen Snyder, Hitoshi Tomaru, Chiaki Toyam and Yasuyuki Muramatsu Iodine as an Indicator of Deep Marine Diagenesis Pore Water Chemistry of Sediments Associated with Methane Generation in Coalbeds of the Shimokita Peninsula 11:30-11:50: GIMS12A035 Kamila Sztybor, Tine L. Rasmussen, Jürgen Mienert, Stefan Bünz and Chiara Consolaro Methane Release from the Seabed and Reliability of the Paleo-Record 11:50-12:10: GIMS12A091 Jean-Philippe Blouet, Patrice Imbert, Anneleen Foubert and Sutieng Ho Evolution of Hydrocarbon Seepage Mechanisms and Flux Through Time Deduced from the Vertical succession of Methane-Derived Authigenic Carbonates: A Case Study from the Vocontian Basin, SE France

12:10-13:00

Lunch

13:00-17:00

City Tour

18:30-21:00

Banquet party

XIV

12th International Conference on Gas in Marine Sediments Taipei, Taiwan, September 1-6, 2014 September 4, 2014 (Thursday)

Oral Session IX Convener: Ian MacDonald 08:30-08:50: GIMS12A047 Ewa Burwicz, Lars Ruepke and Klaus Wallmann Numerical Modeling of the Co-Existence of Dissolved and Gaseous Methane in the Blake Ridge Site-Implications for Gas Hydrate Accumulation Dynamics 08:50-09:10: GIMS12A049 Liwen Chen, Wu-Cheng Chi, Yu-Sian Lin, Shao-Kai Wu, Char-Shine Liu and Yunshuen Wang Geological Processes Affecting the Thermal Structures of Shallow Seafloor 09:10-09:30: GIMS12A071 Wu-Yang Sean, Ren-Yu Ye and Ray-Quan Hsu Meso-scale Modeling of Methane Hydrate Dissociation in Porous Media by using Regular Arrays 09:30-09:50: GIMS12A079 Cheng-Yueh Wu and Bieng-Zih Hsieh Efficiency of Depressurization on Gas Production from Class-1 Hydrate Deposits Offshore Southwest Taiwan 09:50-10:10: GIMS12A081 Ardian Nengkoda, Supranto, Suryo Purwono and Imam Prasetyo Methane Hydrate Production Top Side Facilities Model Case Study Indonesia

XV

10:10-10:30: GIMS12A094 2014 Sep. 4th

Sutieng Ho, Daniel Carruthers, Patrice Imbert, Joe Cartwright and Jean-Philippe Blouet How Geometries of Fluid Venting Structures Are Affected by Spatial Variations of Polygonal Fault Patterns Due to Stress Perturbations 10:30-10:50

Break

10:50-11:20 Poster Session III Convener: Glen Snyder GIMS12A065: Kruglyakova R., Dachnova M., Shevtsova N., Mozhekova S., Terenozhkin Seafloor Fluid Emission in the Khatanga Gulf of the Laptev Sea GIMS12A066: Min-Te Chen Identifying Environmental Impacts from Large-Scale Methane Releasing Events by Using Marine Geological Records Offshore SW Taiwan and the Northern South China Sea GIMS12A073: So-Siou Shu and Ming-Jer Lee Dynamic Behavior of Methane Gas Hydrates Formation and Decomposition with a MidScale Apparatus GIMS12A067: Jyun-Yi Wu and Shiang-Tai Lin A New Force Field for Accurate Thermodynamic Properties of CH4-THF Hydrates GIMS12A070: Shein-Fu Wu, Chen-Feng You, Yen-Po Lin, Eugenia Valsami-Jones and Emmanuel Baltatzis Magmatic Water Contribution in Milos Submarine Hydrothermal Fluids New Boron Isotopic Evidence GIMS12A072: Hung-I Chao, Hsuan Lo and Shiang-Tai Lin Molecular Dynamics Simulation for Quantitative Description of Thermodynamic Properties of Methane Hydrates GIMS12A078: Yan-Yu Chen, David Shan-Hill Wong and Ying-Chih Liao Production Analysis for Depressurized Methane Gas Recovery from Hydrate Reservoir in Offshore Southwestern

XVI

GIMS12A080: Ke-Shu Li, Andrew Tien-Shun Lin and Char-Shine Liu Three-Dimensional Structural and Stratigraphic Architectures and Gas Hydrate Occurrences in a Fault Zone of the Accretionary Wedge off SW Taiwan GIMS12A084: Tsanyao Frank Yang, Tomohiro Toki, Saulwood Lin and Hideaki Machiyama Gas Composition of the Venting Bubbles from the Formosa Ridge in the Gas Hydrate Potential Area, Offshore of SW Taiwan GIMS12A058 : Chuang-Yi Ho and Chin-Chang Hung Methane Flux in the Northern South China Sea GIMS12A050: Sudipta Sarkar, Joerg Bialas, Stephanie Koch, Cord Papenberg, Thomas Eckardt, Felix Gross, Jasper Hoffmann, Ingo Klaucke, Christian Berndt, Bryan Davy, Karsten Kroeger, Ingo Pecher, Kate Waghorn and SO226 Scientific Party Polygonal Fault System and Mud Mobilization in Cenozoic Chalky Limestone of the Chatham Rise, New Zealand GIMS12A086: Stefan Wenau, Zsuzsanna Tóth, Volkhard Spiess, Hanno Keil, Jan-Hendrik Körber, Tai Fei and Dieter Kraus Autonomous Detection, Mapping and Sampling of Marine Gas Seeps Using an AUV GIMS12A042: Matveeva Tatiana, Logvina Elizaveta, Semenova Anastasiya and Alexander Savvichev Spatial Distribution and Turnover of Methane in the Chukchi Sea GIMS12A068 : Tatiana V. Pogodaeva and Tamara I. Zemskaya Evidence of Current Gas Hydrate Formation in The Near-Surface Sediments of Lake Baikal GIMS12A041: Jürgen Mienert, Karin Andreassen, Jochen Knies, JoLynn Carroll, Stefan Buenz, Bénédicte Ferré, Tine Rasmussen, Giuliana Panieri, Catherine Lund Myhre CAGE - Centre for Arctic Gas Hydrate, Environment and Climate GIMS12A059 : Mario Veloso, Marc De Batist, Jens Greinert and Jürgen Mienert Estimation of CH4 Release over a Seep Area Offshore Svalbard Based on an Inverse Hydroacoustic Method GIMS12A075 : Wei-Li Hong, Marta Torres, Malgorzata Peszynska and Ji-Hoon Kim Methane Hydrate Stability and Saturation in Ulleung Basin A Numerical Model Perspective XVII

2014 Sep. 4th

2014 Sep. 4th

GIMS12A031: Alexey Portnov, Jürgen Mienert and Pavel Serov Modeled Evolution of Subsea Permafrost Associated with Extensive Gas Escape Offshore the West Yamal Shelf GIMS12A036 :Pavel Serov, Alexey Portnov, Jurgen Mienert and Petr Semenovet Methane as a Potential Driving Force to Form the Pingo-Like Features at the South Kara Sea Shelf GIMS12A094: Sutieng Ho, Daniel Carruthers, Patrice Imbert, Joe Cartwright and JeanPhilippe Blouet How Geometries of Fluid Venting Structures Are Affected by Spatial Variations of Polygonal Fault Patterns Due to Stress Perturbations 11:20-12:10

Poster Discussion

12:10-13:20

Lunch

Oral Session X Convener: Heiko Sahling 13:30-13:50: GIMS12A048 Sergey Muyakshin Review of the Remote Hydroacoustic Methods for the Quantification of Gas Discharge from Underwater Bubble Seep 13:50-14:10: GIMS12A061 Jens Karstens and Christian Berndt Seismic chimneys in the Southern Viking Graben 14:10-14:30: GIMS12A082 Tzu-Ting Chen, Char-Shine Liu and Charles K. Paull AUV Surveys Reveal Seafloor Asymmetric Depressions and Linear Troughs Along a Fault Zone Offshore Southwest Taiwan 14:30-14:50: GIMS12A060 Zsuzsanna Tóth and Volkhard Spiess Multi-Frequency Imaging and Quantification of Shallow Free Gas

XVIII

14:50-15:10: GIMS12A040 Ewa Burwicz, Elena Piñero and Christian Hensen Influence of 3D Fault Modeling on Gas Migration Pathways and Gas Hydrate Accumulation in Porous Sediments: Case Studies of Hydrate Ridge (Oregon Margin) and Green Canyon (Gulf of Mexico) 15:10-15:30

Break

15:30-15:50

Introduction of field trip

15:50-16:40

General Assembly

16:40-17:00 Closing

XIX

2014 Sep. 4th

12th International Conference on Gas in Marine Sediments Taipei, Taiwan, September 1-6, 2014 September 5-6, 2014 (Friday-Saturday)

Field Trip Day One - 9/5 07:30-11:00 11:00-12:00 12:00-13:30 14:30-15:30 16:00-16:15 17:30-19:00 Day Two - 9/6 07:30-08:30 11:00-12:00 12:00-14:00 15:00-18:30

Bus to 921 Museum in Wufong, Taichung County. Lunch. Bus to Chung-lun (CL) mud pool. Bus to Kuang-tze-ling (KTL) muddy hot spring. Bus to Suei-huo-tong-yuan (SHTY) everlasting fire. Bus to Les Hotel, Tainan.

Bus to Wu-shan-ding (WSD) mud cones, walk to Hsin-yang-nyu-hu (HYNH) mud shield. Lunch. Bus to Chelungpu Fault Preservation Park in Chushan Nantou County. Bus to National Taiwan University.

XX

12th International Conference on Gas in Marine Sediments GIMS 12 Abstract Volume Taipei, Taiwan September 1-6, 2014

Organized by Department of Geosciences, National Taiwan University (NTU)

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session I: September 1st (09:30-10:10) Keynote Speech

Gas Hydrates (Clathrates) in Marine Sediments - Key Questions Miriam Kastner Scripps Institution of Oceanography, La Jolla, CA 92093, USA ABSTRACT Gas hydrates in marine sediments along continental margins constitute an important part of the global carbon cycle. Their distribution and concentration, however, vary from margin to margin and with tectonic environment, and the biogeochemical and hydrological processes that lead to this variability are a focus of ongoing research. Profiles of dissolved chemical constituents and isotope ratios in marine sediments can be used to identify and quantify net rates of microbial and diagenetic reactions including methane production. To establish the structural and lithological controls on gas hydrate distribution and to asses the associated methane fluxes, both non-pressurized and pressurized cores need to be recovered and analyzed. An overview of gas hydrates research with an emphasis on the more recent activities will be discussed. That includes, the occurrence of gas hydrates, gas hydrates and geohazards, the potential contribution of gas hydrates to climate change, the evidence for the Arctic as a source of methane from gas hydrates dissociation, on methane flux to the atmosphere from the ocean, and the consideration and challenge of CO2 - CH4 exchange; extensive experiments on CO2 - CH4 exchange are in progress.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session II: September 1st (10:40-11:20) Keynote Speech

Gas Hydrates in the Climate System Christian Berndt GEOMAR [email protected] ABSTRACT Marine methane hydrate is an ice-like substance stable at high-pressure and low temperature frequently found in continental margins. As the amount of gas hydrate in continental margins is very large, it has long been speculated that gas hydrate dynamics play a role in the climate system. However, ice core data convincingly show that gas hydrate dissociation has not influenced the Pliocene and Pleistocene glacial cycles. It is more difficult to assess the role of gas hydrates during rare events in the Earth history such as the Paleocene Eocene Thermal Maximum for which convincing geological explanations are still lacking. As climate is arguably warming faster than ever before, there is concern that warming bottom waters have already started to dissociate large amounts of marine gas hydrate and may possibly accelerate global warming. New bottom water temperature measurements, seep location maps, and carbonate samples corroborate that hydrates play a role in the observed seepage of gas at the hydrate stability zone and sea floor interception on the continental margin off Svalbard, but it seems seepage off Svalbard has been ongoing for at least three thousand years and that seasonal fluctuations of 1-2°C in the bottom-water temperature cause periodic gas hydrate formation and dissociation, which focus seepage at the observed gas flare depth. These findings imply that decadal scale warming of the West Svalbard Current is at most of minor importance for the bulk of the observed seepage and that the seeps in Svalbard do not necessarily represent the beginning of large-scale hydrate dissociation in the Arctic. But, it also shows that hydrate is highly sensitive to bottom water temperature changes and that bottom water warming will affect the stability of any large hydrate accumulations at the seabed on a short time scale.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session II: September 1st (11:20-11:40)

Post-Accident Discharge Forensics at the Deepwater Horizon Site, Gulf of Mexico Ian R MacDonald, Oscar Garcia-Pineda, Mauricio Silva, Samira Daneshgar-Asl, Caroline Johansen, Chris Reddy, William Shedd Florida State University (IRM, OGP, MS, SDA, CJ), Woods Hole Oceanographic Institution (CR), Bureau Ocean Energy Management (WS), [email protected] ABSTRACT We investigated intermittent hydrocarbon releases at the site of the Macondo well blow-out and the Deepwater Horizon wreckage, which remains on the seabed. Aerial and satellite remote sensing observed layers of hydrocarbons (oil slicks) floating in a vicinity of 2 to 3 km above the site on multiple occasions during September 2012 through January 2013. Analysis of their size and appearance indicated that the slicks comprised on the order of 100 l of oil at any given time, but subsequent surveillance suggested that discharges closest to the wreckage had ceased by April 2013. An acoustic survey of the area in November 2012 discovered plumes of hydrocarbons rising from the wreck itself and from geologic features in the 10-km region around the well. Analysis of hydrocarbons collected from the sea surface, from an abandoned containment dome, and from seabed sediments indicated the following potential sources: unaltered oil from the Macondo well, Macondo oil contaminated with traces of drilling mud, oil similar to Macondo oil discharged from natural seeps, and oil from natural seeps with a distinct chemical signature. Observations from the ALVIN submersible illustrate the differences between accidental discharge and natural seeps. The complexity of possible sources and potential hydrocarbon pathways documents how difficult it is to reach conclusions regarding the discharge status of a post-accident setting. Effective monitoring at the DWH site will require careful application of complimentary technical approaches.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session II: September 1st (11:40-12:00)

Methane Flux in Gas Hydrate Potential Areas off SW Taiwan Tsanyao Frank Yang, Nai-Chen Chen, Chin-Yi Hu, Pei-Chuan Chuang, Hsuan-Wen Chen Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan [email protected]

Saulwood Lin Institute of Oceanography, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan [email protected]

San-Hsiung Chung, Yunshuen Wang, Po-Chun Chen Central Geological Survey, MOEA, No. 2, Ln. 109, Huaxin St., Zhonghe Dist., New Taipei City 23568,Taiwan [email protected] ABSTRACT The widely distributed BSRs imply the existence of potential gas hydrates in offshore southwestern Taiwan. To better constrain the gas sources in this area, in total 22 cores have been collected from different tectonic environments in offshore SW Taiwan during the r/v Marion Dufresne 178 cruise, including 17 giant piston cores, 4 CASQ box cores, and 1 gravity core. The results show that the major gas is methane with very few ethane and carbon dioxide. It indicates they are mostly biogenic source in origin. However, some gas samples from active margin do also exhibit heavier carbon isotopic compositions, which range from -40 to -60 permil and are similar with the gas composition of inland mud volcanoes of SW Taiwan. It implies that there is also thermogenic gas source in this region. Total changes of the dissolved inorganic carbon (DIC) fluxes can be used to estimate the methane flux quantitatively, and we confirm that the sulfate depletion is mainly controlled by the anaerobic oxidation of methane (AOM) reaction and/or the sedimentary organic matter in this area. Although BSRs are widely distributed both in the active margin and in the passive margin, the methane fluxes in active margin are higher than in passive margin of the coring sites. Therefore, we consider that different tectonic settings in offshore SW Taiwan might strongly control the stability of gas hydrates, and then affect the methane concentrations and fluxes of the cored sediments.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (13:30-13:50)

Quantification of Gas Emissions at the Continental Margin West of Svalbard Heiko Sahling, Miriam Römer, Thomas Pape, Christian dos Santos Fereirra, and Gerhard Bohrmann MARUM – Center for Marine Environmental Sciences and Department of Geosciences University of Bremen, Germany [email protected], [email protected], [email protected], [email protected], [email protected]

Benoît Bergés Institute of Sound and Vibration Research, University of Southampton, U.K. [email protected] ABSTRACT The continental margin west of Svalbard has become a natural laboratory for studying the gas and gashydrate system in a warming ocean. Research efforts in that area have intensified since the alarming findings by Westbrook et al. (2009) of intensive gas bubble emissions along a band just landward of the 396-m depth contour, which is the current upper limit of the gas hydrate stability zone (GHSZ). In the region the bottom water has warmed by about 1°C in the past 30 years. Such a temperature increase was proposed to have shifted the upper boundary of the GHSZ downward from ~360 m water depth 30 years ago to 396 m today and to induce gas hydrate dissociation causing the observed gas bubble emissions. Reagan et al. (2011) modeled the global-warming induced amount of methane liberated by dissociating hydrates at the continental margin west of Svalbard revealing that 8800 mol methane can be released per meter of margin segment per year. In order to quantify the amount of methane that is emitted as gas bubbles from the seafloor to the water column we studied the area with the German R/V Heincke (He-387) in late summer 2012 (Sahling and cruise participants, 2012; Sahling et al. submitted). We combined systematic water column hydroacoustic mapping with seafloor investigations with the remotely operated vehicle (ROV) Cherokee to quantify the bubble flux: At first, we systematically surveyed the area with multibeam echosounder (Kongsberg EM 710) and estimated the number of flares by manually picking these in the water column data using FM Midwater of the Fledermaus program package. Next, we estimated the number of bubble streams that contributed to a single flare employing the horizontally-looking scanning sonar Imaginex 881A mounted on the ROV. Subsequently, we measured the gas volume flux of individual bubble streams either by use of an inverted funnel for capturing the gas or by interpreting the ROV video footage. Finally, we sampled the gas and analyzed its composition. By repeating all these measurements, we calculated average methane fluxes and estimated the range of uncertainty (min/max). Our calculations revealed that about 53 x 106 mol methane (min: 9 x 106, max: 118 x 106 mol) were annually emitted at the ~14-km long band of flares at the continental margin west off Svalbard. These amounts show that gas emissions at the continental margin west of Svalbard were in the same order of magnitude as bubble emissions at other geological settings (e.g. Römer et al., 2014). The values correspond to fluxes of 6000 mol methane (min: 1100, max: 15100 mol) per meter of margin segment per year, which is in the same order of magnitude as model-based estimates of the amount of methane released from dissociating hydrate (Reagan et al. 2011). Our estimate may serve as baseline estimate (year 2012) of the bubble flux that will potentially increase in future due to ever-increasing global-warming induced bottom-water warming and hydrate dissolution.

7

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (13:30-13:50) However, research at the continental margin west of Svalbard is continuing and exciting discoveries can be made. Very recently, Berndt et al. (2014) posed a new hypothesis of a seasonally varying thickness of the GHSZ. Uranium-Thorium-dating on massive methane-derived authigenic carbonates sampled at the seafloor at the 396-m flares (‘MASOX site’) revealed ages of up to three thousand years. These findings suggest a long history of methane venting in the area, which argues against the hypothesis of recent global warming-induced hydrate decay. In addition, seasonal fluctuations of 1-2°C in the bottom-water temperature measured with a seafloor-deployed mooring over a period of almost two years might cause periodic hydrate formation and dissolution (Berndt et al., 2014). However, a seasonally growing and declining thickness of the GHSZ should, consequently, result in seasonal fluctuations in gas bubble emissions, with more intensive emissions during the time of a retreating GHSZ from about June to December (warmer bottom water) and less intensive (or no) emissions from January to May (colder bottom water). These recent finding call for an initiative to monitor the gas emissions continuously through a year, and, as warming continues, in the near future.

REFERENCES Berndt, C., T. Feseker, T. Treude, S. Krastel, V. Liebetrau, H. Niemann, V.J. Bertics, I. Dumke, K. Dünnbier, B. Ferré, C. Graves, F. Gross, K. Hissmann, V. Hühnerbach, S. Krause, K. Lieser, J. Schauer, and L. Steinle (2014), ”Temporal Constraints on Hydrate-Controlled Methane Seepage off Svalbard,” Science, 343, 284287. Reagan, M.T., G.J. Moridis, S.M. Elliott, and M. Maltrud (2011), “Contribution of oceanic gas hydrate dissociation to the formation of Arctic Ocean methane plumes” Journal of Geophysical Research: Oceans, 116, C09014. Römer, M., H. Sahling, T. Pape, C. dos Santos Ferreira, F. Wenzhöfer, A. Boetius, and G. Bohrmann (2014), “Methane fluxes and carbonate deposits at a cold seep area of the Central Nile Deep Sea Fan, Eastern Mediterranean Sea,” Marine Geology, 347, 27-42. Sahling, H. and Cruise Participants (2012), “R/V Heincke cruise report HE-387. Gas emissions at the Svalbard continental margin. Longyearbyen - Bremerhaven, 20 August - 16 September 2012,“ Berichte, MARUM Zentrum für Marine Umweltwissenschaften, Fachbereich Geowissenschaften, Universität Bremen, 291, p. 170. Sahling, H., M. Römer, T. Pape, B. Bergés, C. dos Santos Fereirra, J. Boelmann, P. Geprägs, M. Tomczyk, N. Nowald, W. Dimmler, L. Schroedter, M. Glockzin, and G. Bohrmann (subm.), ”Gas emissions at the continental margin west off Svalbard: mapping, sampling, and quantification,” Biogeosciences Westbrook, G.K., K.E.Thatcher, E.J. Rohling, A.M. Piotrowski, H. Pälike, A.H. Osborne, E.G. Nisbet, E.A. Minshull, M. Lanoisellé, R.H. James, V. Hühnerbach, D. Green, R.E. Fisher, A.J. Crocker, A. Chabert, C. Bolton, A. Beszczynska-Möller, C. Berndt, and A. Aquilina (2009), ”Escape of methane gas from the seabed along the west Spitsbergen continental margin,” Geophysical Research Letters, 36, L15608.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (13:50-14:10)

Are Cold Seep Locations Controlled by Topography or Gas Hydrate Distribution? A View from the Kerch Seep Plumbing System in the Black Sea Timo Zander, Ingo Klaucke, Jörg Bialas, Christian Berndt, Dirk Kläschen, Cord Papenberg GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstr. 1-3, 24148 Kiel, Gemany [email protected], [email protected], [email protected] ABSTRACT Cold seeps seem to develop preferentially at or near the crests of ridges or other local topographic highs (e.g. Johnson et al., 2003; Klaucke et al., 2006; Greinert et al., 2010). Although conclusive reasons for this widespread phenomenon have not been offered it implies that topography is a primary control on the distribution of cold seeps. It has been suggested that free gas migrates laterally along the base of the gas hydrate stability zone or within the hydrate stability towards the crest of the structure. Recent high-resolution surface (deeptowed sidescan sonar) and subsurface (Chirp, high-resolution 3D-seismic) data of the Kerch seep and plumbing system in the Black Sea challenge this view. The Kerch seep site is located in 890 – 940 m water depth south of the Kerch Strait in the northern Black Sea, and consists of three individual seafloor mounds with an elevation of about 1 to 10 m from the surrounding seafloor and covering an area between 0.03 to 0.2 km². A remarkable feature of these seeps is the fact that one seep developed on the crest of a levee, one on the flank, and one in the channel bed (Fig. 1).

Fig. 1: Shallow subsurface of the Kerch seep site highlighting the development of three individual seeps on top of a levee (A), on the levee-flank (B), and in the channel sediment bed (A). The base of the channellevee system is highlighted by high-amplitude reflections. Reflective zones in shallow depth indicate free gas accumulations. The levees show numerous subvertical faults (blue lines). 9

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (13:50-14:10) Each of the seeps is currently active as evidenced by gas bubble streams (flares) escaping into the water column at the margins of the mounds. Individual gas accumulations are present in shallow depths of about 5-10 m below the seafloor (Fig. 1). 3D seismic data and coherency maps show the presence of numerous sub-vertical faults on the levees with lateral extensions of up to 1000 m, which often can be traced down below the base of channel deposits (Fig. 1). A BSR is not visible in the seismic data, but the presence of gas hydrates has been confirmed for the mounds in shallow depth (Römer et al., 2012). The faults in the levees are post-depositional and some act as migration pathways for rising gas through the GHSZ towards the seafloor as evidenced by reflector pull-ups. However, other faults in the close vicinity do not appear to have acted as a fluid conduit. As for the seep in the coarse-grained channel bed: intermediate gas accumulations indicated by bright spots in channel sediments (Fig. 1) are expected. Faults in the channel sediments are not imaged due to a chaotic seismic character of the deposits, but we expect the presence of weak zones and fractures that favor focused fluid ascent towards the seafloor. Vertical reservoir connectivity and permeability should, in our view, result in a much wider seafloor expression of the seep. In the area of the Kerch seep site the base of the gas hydrate stability zone coincides with high amplitude reflection packages at the base of the levee succession. Differences in pressure build-up in this intermediate reservoir govern the location of seeps at the surface rather than topography. The actual source of the gas has not been imaged but lies much deeper. REFERENCES Greinert, J., Lewis, K.B., Bialas, J., Pecher, I.A., Rowden, A., Bowden, D.A., De Batist, M., Linke, P., 2010. Methane seepage along the Hikurangi Margin, New Zealand: Overview of studies in 2006 and 2007 and new evidence from visual, bathymetric and hydroacoustic investigations. Marine Geology 272, 6-25. Klaucke, I., Sahling, H., Weinrebe, W., Blinova, V., Bürk, D., Lursmanashvili, N., Bohrmann, G., 2006. Acoustic investigations of cold seeps offshore Georgia, eastern Black Sea. Marine Geology 231, 51-67. Johnson, J.E., Goldfinger, C., Suess, E., 2003. Geophysical constraints on the surface distribution of authigenic carbonates across the Hydrate Ridge region, Cascadia margin. Marine Geology 202, 79-120. Römer, M., Sahling, H., Pape, T., Bahr, A., Feseker, T., Wintersteller, P., Bohrmann, G., 2012. Geological control and magnitude of methane ebullition from a high-flux seep area in the Black Sea – the Kerch seep area. Marine Geology 319-322, 57-74.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (14:10-14:30)

The Anomalies of Natural Gases in the Sediments and Seawater in the Gulf of Tonkin (BacBo, South-China Sea), Vietnam Shakirov Renat1,3, Nguyen Nhu Trung2,3, Duong Quoc Hung2, Syrbu Nadezhda1,3, Le Duc Anh2,3, Mal’tseva Elena1,3, Telegin Iurii1, Polonik Nikita1, Obzhirov Anatoly1 1

V.I. Il'ichev Pacific Oceanological Institute FEB RAS, Vladivostok City (Russia); [email protected] 2 Institute for Marine Geology and Geophysics VAST, Hanoi City (Viet Nam) 3 Joint Vietnam-Russia Laboratory for marine science and technology, POI FEB RAS – IMGG VAST ABSTRACT For the first time, as a result of joint gas geochemical and geophysical research in the northern part of a Gulf Tonkin and on islands Kat Ba and Koto the valuable data about distribution of methane, hydrocarbon gases, helium, hydrogen and other natural gases related to the geological structures has been obtained. Goal of study: to determine the natural gases (methane, hydrocarbon gases, helium, hydrogen, nitrogen and others) related to the tectonic pattern and geological structures on the study area based on gasgeochemistry and high resolution seismic data processing and interpreting. Keywords: Vietnam, Gulf of Tonkin (BacBo), methane, propane, butane, helium, hydrogen, tectonics PREFACE The study area is Bac Bo basin located by the northeast of the Red River basin in the Gulf of Tonkin (fig. 1), including Ha Long Bay, one of seven world wonders awarded by UNESCO for landscape, geological and geomorphology values. It is situated in very special location in the western end of Beibu Basin that it is affected by the two tectonic phase activities producing the NE-SW strike slip Red River fault in the western site and the NE-SW fault system crossing the Beibu Basin. A number of sediment basins and tectonic depression with hydrocarbon promising sediments and underlying carbonate thickness was created in this area. There are number of the promising tectonic evidences of oil and gas plays dated Oligocene and Miocene in this area. The basement depth of the Bac Bo basin ranges from some kilometers in the margin to 8.2 km in the depocenter. The structural elements of the Bac Bo basin are oriented NE-SW and E-W directions. There are NE-WE and E-W depression and NE-SW and E-W uplifts.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (14:10-14:30)

Study area Fig. 1. Study area and geophysical-geological profiles (left).Sampling stations (total sediment and seawater) in BacBo configured on several profiles and follow to geophysical survey. Captured legend: 1 – sampling stations and their number; 2 – sampling site and its number; 3 – tectonic faults; 4 – coal deposits (right figure). METHODS Sediment sampling was conducted by stainless gravity corer (length 100 cm, weight 50 kg, POI), water sampling performed by NISKIN bottles (fig. 2). The sediment cores length recovered about 65 cm. The sediment cores were subsampled along by syringes. Seawater was sampled on 2 levels: surface and bottom.

Fig. 2. Joint sediment and water sampling in the expedition, BacBo, 2013.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (14:10-14:30)

On some stations the silt was colored by red spots. The comprehensive GC, GC/MS and organic carbon analyses were conducted. The geophysical scope was performed by: 1-High resolution seismic data sets obtained by Project KC-09-09 survey (Sparker source GEONT’97, May 2013) and other available surveys on the area; 2-Petroleum seismic data; 1’x1’ Satellite gravity and 2’x2’ magnetic data are available and gotten free all over the sea world. 97 stations of sediment and water sampling on 6 profiles were conducted in the northwest of Bacbo (East-Vietnam Sea), 2013. Helium, hydrogen, methane, hydrocarbon gases, nitrogen, carbon dioxide, oxygen were analyzed in sediments and sea water. The basement depth of the Bac Bo basin ranges from some kilometres in the margin to 8.2 km in the depocenter. The structural elements of the Bac Bo basin are oriented NE-SW and E-W directions. There are NE-WE and E-W depression and NE-SW and E-W uplifts. RESULTS AND DISCUSSIONS The sediment of the study area actually presented by silt with admixtures of sand, also silt sand was distributed; hard rock’s sites and shells were found. Most samples of surface sediments related to terrigenous sources with admixtures of biogenic origin. Main minerals by decreasing: feldspar, quartz, carbonates pieces, amphiboles, biotite, zircon. In the eastern part of study area the pyritization of foraminifera detected and authigenic pyrite (1-2%) formation observed. Among biogenic components the carbonate containing organisms (foraminifera and pieces of shells (10-50%) and silica organisms (diatoms and sponges spicules) (5-20%) calculated. Organic carbon vary in 0.25-1.23 % and well correlated with pelite sediments. Inorganic carbon found from 0 to 1.69%. From the coast toward the sea the organic carbon content gradually decreasing and inorganic carbon content increasing. Methane (up to 370 nMol/kg) and hydrocarbon gases (ethane, propane, and butane) were found in the sediments in valuable concentrations, as well as helium (20 ppm average) and hydrogen (up to 100 ppm) content indicates certain geological structures. Carbon dioxide and methane dissolved in the sea water show their normal and abnormal distribution. The relations of gases can tell us new information of geological structures and ecology state of study area. Permeability zones also provide the greenhouse gases slight emission (methanecarbon dioxide) from interior into the atmosphere. Background concentration of helium in sediments is 10.4 ppm, and hydrogen - 6.4 ppm. In sea water background concentration of helium make 8.55 ppm, hydrogen - 4.5 ppm. The raised background of helium and hydrogen, probably, is connected, with presence of a deep zone of permeability and seismo-tectonic activity. Presence in sediments and sea water of hydrocarbon gases, such as ethane, propane and butane specify on lithospheric source of these gases. background concentration of methane in bottom sediments in the Gulf of Tonkin is 155 nMol/kg. In the groundwater on islands KatBa and Koto, concentration of dissolved methane is unstable enough and varies in wide range. Anomalies reach huge values of 105 mkl/l. For comparison, it is in 10 times more than on oil-and-gas bearing shelf of Sakhalin Island (Sea of Okhotsk). Heavy hydrocarbons (butane, pentane) in concentration to 0,00003 % have been found out in all samples with abnormal concentration of methane. All sampling area can be subdivided in to 6 sites included profiles and cross profiles (fig. 1). Methane was found in all sediment samples (fig. 3), and ethane was detected in the 95 % of samples. Ethane concentrations are 10 times less than methane concentrations, but sometimes have the same values, e.x. 1051 nl/l on station 73. Propane and butane were found also, in the 75-80% of samples. Methane concentrations in the sediments vary actually from 45 to 270 nano-mol/kg. Such concentrations are marks slight methane amount in the surface sediments and indicate usually effective lithologycal cap, trapped possible hydrocarbons.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (14:10-14:30)

Fig. 3. Methane anomalies (map plot), GC record with hydrogen peak, hydrocarbon gases content in the sediments and dissolved in the seawater. The biggest dissolved methane content 18 ml/l accompanied by hydrocarbon gases was found in the mouth of the Red River (hydrological freshwater spring), probably indicates permeability of thermogenic gases of Red River rift system. Dissolved gases show steady methane concentrations around 15 nl/l, but hydrocarbon gases exposed abnormal values, especially butane (found on all sites) and pentane (found on Sites II and III). Also, methane distribution in the seawater does not show influence of coal deposits on the coast. For our experience coal caused significantly exceeds of normal methane distribution in case of gas flux from the coal layers. But according to our data we did not fill coal gas contribution. Helium content shows near the normal distribution with slight anomalies in the sediments. In opposite, we found many hydrogen anomalies (up to 700 ppm, st. 72, Site1 IV) exceeded the background 100 times. These anomalies definitely related to geologic structures, such as faults (fig. 4, fig. 5). Also, hydrogen anomalies indicate seismic activity of tectonic faults. Hydrogen in sediments

Fig. 4. Hydrogen anomalies in the sediments of BacBo. 14

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (14:10-14:30)

Fig. 5. Sketch map of fault system obtained during expedition. By the GC/MS analyses we obtained 3 groups of organic matter. In the third group linear alkanes C10C24 were fixed, and the most important the pristane/phytane isoprenoid hydrocarbons - certain markers of hydrocarbon accumulation was found. In the all three groups of dispersed organic matter was formed from sea sources in the past: 1 - group - mainly from algae, 2 and 3 - algae and microfauna. CONCLUSIONS The first results on gasgeochemistry survey of sediments and seawater in the north BacBo revealed valuable data set concerning methane, hydrocarbon gases, helium, hydrogen and others distribution. Methane concentrations reached 8200 nano-liters/kg in sediments, and hydrocarbon gases such as ethane, propane, and especially butane and pentane indicates geological sources of this gases. Thermogenic gases according to the relations between gases are detected. Observed anomalies of natural gases induced by: 1) hydrocarbon sources such as accumulations in the host rocks and 2) active tectonic pattern caused faulting and folding and ancient rocks. Hydrogen anomalies up to 700 ppm indicates geotectonic activity of certain geological structures such faults. The Bac Bo basin is a large basin with the deepest basement is 8.2 km in the depocenter. It is separated with the Red River Basin in the west by the NW-SE faults. The basin was formed and dominated by the regional NE-SW Halong fault in the north and South Bac Bo fault in the south. The Bac Bo basin has NE-SW and W-E depressions in which the W-E depressions are deeper than the NE-SW ones. The NE-SW uplifts are occurred in the NE and SW parts of the basin. There are the NE-SW, WE and N-S faults in the basin, in which the NE-SW faults are the biggest and dominated the basin. The N-S faults are smallest. Gasgeochemistry and seismic evidences to convince the N-S predicted faults being active. The advantage of the 3D said interpretation procedure could be very useful and effective to determine the basement structure of the basins. Data processing and interpretation will definitely allow us to develop joint complex gasgeochemical and geophysical study in BacBo and Hanoi Basin.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (14:10-14:30) ACKNOWLEDGMENTS These results were obtained in the frame of joint Russia-Vietnam RFBR-VAST project No. 13-05-93000 “STUDY ON HYDROCARBON GAS-GEOCHEMICAL FIELDS AND GEODYNAMICS IN THE GULF OF TONKIN, VIETNAM: IMPLICATION FOR HYDROCARBON RESOURCES AND TECTONICS” and Vietnam State project “GENERAL INVESTIGATION ON GEOLOGICAL AND GEODYNAMIC CONDITIONS AIMS AT PLANNING ECONOMICAL DEVELOPMENT IN THE NORTH OF GULF OF TONKIN” (KC-09-09, head Dr. Nguyen Nhu Trung). The study partially supported by grant of Russian Fund for Basic Research 14-05-00294.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (14:30-14:50)

Surface Expression of Cold Seeps on the Continental Margin Offshore SW Taiwan Ingo Klaucke1, Saulwood Lin2, Christian Berndt1 and SO227 Scientific Party 1

GEOMAR, Helmholtz-Centre for Ocean Research Kiel, Kiel, Germany Dept. of Oceanography, National Taiwan University, Taipei, Republic of China

2

ABSTRACT Cold seeps are a widespread phenomenon along the continental margin of SW Taiwan on both the active and the passive margin (Lin et al., 2007; Chen et al., 2010; Chuang et al., 2010). Many of these cold seeps are active today and they are particularly well documented on the well-developed accretionary ridges of the active margin, where a large number of mud volcanoes have been documented (Chen et al., 2010). The incipient and relatively young accretionary ridges at the foot of the accretionary prism, however, have been considered as closed systems, where particularly large concentrations of methane hydrate could be found. Recent sidescan sonar data obtained during RV SONNE cruise SO227 in April 2013, however, challenge the view of closed systems in this area. Four Way Closure Ridge centred at 22°02’N and 119°48.5’E in roughly 1500 metres water depth shows high backscatter anomalies that indicate fossil cold seep environments and that correlate well with fluid flow pathways imaged by high-resolution 3D seismic data. Similar high backscatter anomalies indicating various degrees of relief have also been observed on an adjacent ridge to the South of Four Way Closure Ridge. Here at least three different cold seep sites probably representing different ages can be distinguished (Fig. 1).

Figure 1: Sidescan sonar swath showing three individual cold seeps highlighted by high backscatter intensity (light tones). Different degrees of surface roughness resulting in different backscatter pattern may result from different ages of the seeps.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (14:30-14:50) The presence of cold seeps on this relatively young accretionary ridge close to the deformation front raises the question of how seepage develops. Are the locations of seeps determined by the distribution of reservoir facies (channel deposits) in the sedimentary succession, or do they result from the creation of pathways during the deformation process? The different possible working hypotheses shall be presented.

REFERENCES Chen, S.-C., Hsu, S-K., Tsai, C.-H., Ku, C.-Y., Yeh, Y.-C., Wang, Y. (2010) Gas seepage, pockmarks and mud volcanoes in the near shore of SW Taiwan, Mar. Geophys. Res., 31: 133-147. Chuang, P.-C., Yang, T.F., Hong, W.-L., Lin, S., Sun, C.-H., Lin, A.T.-S., Chen, J.-C., Wang, Y., Chung, S.-H. (2010) Estimation of methane flux offshore SW Taiwan and the influence of tectonics on gas hydrate accumulation, Geofluids, 10: 497-510. Lin, S.W., Lim, Y.C., Liu, C.S., Yang, T.F., Chen, Y.-G., Machiyama, H., Soh, W., Fujikura, K. (2007) Formosa ridge, a cold seep with densely populated chemosynthetic community in the passive margin, Southwest of Taiwan. In: Proceedings of the International Conference on Gas Hydrate: Energy, Climate and Environment. October 4–5, Taipei, Taiwan, pp. 71–72.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (14:50-15:10)

Real Time Sea Bed Shallow Sounding for Resistive or Conductive Target Layer Wen J Whan ; K. M. Tsai & Hsiupo Yeh 3JTech Co., Ltd. [email protected]

Jiann-Lin Chen Dept. of Mechanical and Automation Eng., I-Shou Univ. [email protected]

Jeng-Yu Lin Dept. of Chemical Eng., Tatung Univ. [email protected]

ABSTRACT This paper presents a time domain controlled source electromagnetic (CSEM) exploration system for a real-time sea bed shallow sounding using a vertical wire source. Layer earth numerical modeling is applied to study the sensitivity and dynamic range of the electrical and magnetic field needed for a reduced size system in order to facilitate the marine operation. INTRODUCTION Marine controlled source electromagnetic (CSEM) survey has been applied for oil and gas exploration successfully. The ability to determine the resistivity of deep drilling targets from the seafloor may well make marine CSEM the most important geophysical technique to emerge since 3D reflection seismology (S, Srnka LJ. 2007). It is known that vertical transmitter has less effect from the sea water. Considering the marine operation, it is advantageous to keep the vertical wire transmitter and the separation between the transmitter and the receiver as short as possible while keeping a reasonable depth of investigation. Assuming a 1.5 meter long vertical wire transmitter, numerical modeling using layer earth is presented to investigate the sensitivity and dynamic range needed for a short separation between the transmitter and receiver, which would facilitate the marine operation. A dragged vehicle mounted with a vertical transmitter and receiver is proposed for the field testing. The vertical potential field will be measured and interpreted in real time while the vehicle is towed toward the seashore. The vibration of the system is measured by the embedded tilt meter. The influence of the interpretation due to the vibration of the system will also be studied.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (14:50-15:10) SENSITIVITY AND DYNAMIC RANGE ANALYSIS BY NUMERICAL MODELING The layer earth modeling is applied to investigate the sensitivity and dynamic range needed for the system design. Fig. 1 represents the earth model and its Cartesian system. The vertical wire transmitter (Tx) is located on the sea bed. The electrical and magnetic field receivers (Rx) are also located on the sea bed. The separation between the Tx and Rx is kept at 2 meters. The resistivity of first layer below the sea bed is assumed to be 1 ohm-m while the thickness will be changing from 2, 5, 10, 20, 50 meters and infinity.

x

y

z

R x

1 5

0.3 Ohm-m

T x

20uS

20u S

Sea Level

1 OhmResistive target layer: 500mOhm-

Sea Bed 10 mS

m

Fig. 1: The earth model with the Cartesian system and the transmitting current waveform used for the numerical modeling. Fig. 2a and Fig. 2b represent the numerically calculated Ez and By field respectively for a resistive target layer of different depths. From Fig. 2a, in order to distinguish the resistive target at 50 meter deep, the resolution of 10-8 V/M and dynamic range of about 90 dB would be needed. From Fig. 2b, one pico Tesla resolution and dynamic range of 90 dB would be needed. Fig. 3a and Fig. 3b represent the numerical calculated Ez and By field respectively for a conductive target layer of different depths. From Fig. 3a, in order to distinguish the conductive target at 50 meter deep, the resolution of 10-8 V/M and dynamic range of about 90 dB would be needed. From Fig. 3b, one pico Tesla resolution and dynamic range of 90 dB would be needed. The sensitivity and dynamic range are achievable using nowadays electronic and sensor technologies. -3

-2

-2

-1

0

1

2M

-3

5M Ez ( V/M in log)

-4 10 M -5 20 M -6 50 M -7 Infinity -8 Time (ms in log)

Fig. 2a: Calculated Ez field for a resistive target layer of different depth with the system configuration shown in Fig. 1. 20

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (14:50-15:10)

-2

-7

-1

-8

By(Tesla in log)

-3

0

1

2M

-9

5M

-10

10 M

-11

20 M

-12

50 M

-13

Infinity

-14 Time (ms in log) Fig. 2b: Calculated By field for a resistive target layer of different depth with the system configuration shown in Fig. 1. -3

-2

-1

-2

0

1

2

2M

-3

Ez ( V/ M in log)

5M -4 10 M -5 20 M -6 50 M -7 infinity -8 Time (ms in log)

Fig. 3a: Calculated Ez field for a conductive target layer of different depth with the system configuration shown in Fig. 1. -3

-2

-1

-7

0

1

2

2M

By( Tesla in log)

-8 5M -9 10 M -10 20 M -11 50 M -12 infinity -13 Time (ms in log) Fig. 3b: Calculated By field for a conductive target layer of different depth with the system configuration shown in Fig. 1. 21

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (14:50-15:10)

PROPOSED DRAGGED VEHICLE FOR TEST SURVEY CLOSE TO THE SEASHORE In order to carry out a test survey, a dragged vehicle mounted with vertical wire transmitter and potential electrodes as shown in Fig. 4 is designed. The system connected with armored cable will be sunk to the sea bottom after towed with buoy by a small boat to about 2,000 meters away from the seashore. The system is then towed with a winch located on the shore. The data stacked in one second will be sent continuously to the base station on the coast and inverse-interpreted in real time. The vibration and the orientation of the system will be recorded with a tilt meter. The influence of the interpreted earth model and the vibration of the system will be correlated.

Fig. 4: A dragged vehicle of 4 meter long mounted with 1.5 meter vertical wire transmitter and a pair of potential electrodes at 1 meter apart CONCLUSIONS From numerical modeling, a system with the expected sensitivity and dynamic range of the electrical and magnetic field using a vertical wired transmitter could be designed with nowadays electronic and sensor technologies. Measuring the vertical electrical field and the y component of the magnetic field seem to yield the same resolution. Increasing the sensitivity and dynamic range of the receiver, the length of the vertical transmitter and the separation between the transmitter and receiver could be reduced. The field operation is therefore easy to be carried out. A pilot survey using a dragged vehicle towed toward the seashore should help the designing of a dragged or floated system towed by a vessel. REFERENCES S, Srnka LJ. 2007. An introduction to marine controlled-source electromagnetic methods for hydrocarbon exploration. Geophysics. 72:WA3-WA12.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (15:10-15:30)

Helium and carbon flux from shallow submarine hydrothermal system in the Tokara Islands, Southwestern Japan Y. Sano, H. Wen, T. Kagoshima, N. Takahata, Y. Tomonaga, A. Ishida, K. Tanaka and K. Shirai Atmosphere and Ocean Research Institute, University of Tokyo, Japan [email protected]

J. Ishibashi Department of Earth and Planetary Science, Kyushu University, Japan [email protected]

H. Yokose Department of Earth Sciences, Kumamoto University, Japan [email protected]

U. Tsunogai Department of Earth and Environmental Sciences, Nagoya University, Japan [email protected]

T.F. Yang Department of Geosciences, National Taiwan University, Taiwan [email protected] ABSTRACT In order to study the volatile geochemistry of shallow hydrothermal system and risk management of submarine volcano, we have carried out a research cruise of R/V Shinsei Maru (KS-14-10) in a region from Kagoshima bay in Kyushu to an adjacent sea of Amami Oshima. Based on the multi beam echo sounder survey, significant gas plume was discovered at a few hydrothermal sites in the Tokara Islands. Seawater samples were collected by CTD-CMS hydrocasts at the gas plume site where pH and turbidity anomalies were observed. In the laboratory, helium isotope measurement together with methane analysis are now undergone. These data may provide helium and carbon flux from a shallow marine hydrothermal system. INTRODUCTION Geochemical cycle of carbon is well studied in the Earth’s surface because it is an important element of fossil fuel and global warming (Falkowski et al., 2000). The surface material cycle would amount to about 20% of the Earth’s carbon inventory, while the 80% may be related to the element originated in the mantle and deep in the crust (Saal et al., 2002). Therefore deep carbon cycle is an important issue and international research projects were set up several years ago. Even though carbon flux is estimated in significant number of subareal volcanoes (Hilton et al., 2002), the flux data from submarine volcanoes are not well documented. There are several methane data in mid-ocean ridges and back arc spreading systems (Sano & Fischer, 2013). They are derived from deep ocean bottoms, 1000m – 3000m. On the other hand, shallow hydrothermal system of a few 100m is not intensively studied yet. 23

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (15:10-15:30) Helium isotopic ratio (3He/4He) is the most important tracer of mantle derived materials. Elemental abundance ratio to carbon (C/3He) together with carbon isotopes (13C value) may provide a key information on the origin of carbon (Sano & Marty, 1995). In addition the depth gradient of helium concentration in seawater may give the flux from the sea bottom. When the 3He flux is obtained, it is possible to estimate the carbon flux based on the elemental ratio (C/3He) and 3He flux. The first purpose of this work is to study the origin of methane and carbon dioxide in shallow marine hydrothermal systems. The second purpose is to estimate the helium and carbon flux in the region. These data may be useful in the research of deep carbon cycle and the risk management of submarine volcano in future. EXPERIMENTAL Remote sensing observation and seawater sampling were carried out in the volcanic and geothermal regions from Kagoshima bay in Kyushu to Amami Daiichi Kaikyu close to Amami Oshima by the multi beam echo sounder survey and CTD-CMS hydrocasts during the R/V Shinsei Maru KS-14-10 cruise (25th June – 5th July, 2014). Field observations were mostly focused on the shallow submarine hydrothermal system adjacent to the Tokara Islands where new volcanic activity has been reported. After the gas plume signature was taken by water column image, seawater samples were collected by Niskin bottles at the necessary depth. Samples for helium measurement were transferred from the bottles into copper tubes using thick wall Tygon tube without exposure to the atmosphere. Both ends of copper tubes were sealed by stainless steel clamps for storage. For methane analysis, samples were carefully transferred into 125 mL glass vials without air bubbles by the Teflon tubes connected with Niskin bottles. About 0.6 mL of saturated mercury chloride solution was added into the sample for sterilization. Then vials were sealed and kept in a refrigerator until analysis. In the laboratory on shore, gas dissolved in the seawater of copper tube was extracted by head space method and introduced into helium purification and separation vacuum line. After the purification using two Ti getters and charcoal traps held at liquid nitrogen temperature, the 4He/20Ne ratio was measured by on-line QMS system. Then helium was separated from neon by a cryogenic charcoal trap. The 3He/4He ratio was analyzed by a conventional noble gas mass spectrometer (Helix-SFT, GV Instrument) and calibrated against our in house standard (Sano et al., 2008). Methane concentrations of glass vial samples were measured by a standard method together with carbon isotopes by a conventional stable isotope mass spectrometer.

Results and Discussion Observed 3He/4He and 4Ne/20Ne ratios of seawater samples collected in this work vary significantly from 1.01 Ra (where Ra is the atmospheric 3He/4He ratio of 1.382x10-6; Sano et al., 2013) to 2.45 Ra and from 0.254 to 0.352, respectively. There is a positive relationship between the 3He value (where the value is defined as (R - 1) x 100) and excess 4He/20Ne ratio relative to the air saturated seawater value at the ambient temperature, suggesting two component mixing between the atmospheric and volcanic noble gases. The end member for Kagoshima bay samples shows subduction-type mantle helium signature with about 7 Ra, while that for the Tokara Islands indicates more crustal value of about 4 Ra. Both regions are located in the volcanic front of the Ryukyu arc and its extension. So tectonic settings are resemble each other. However observed helium isotopes are different and more crustal signature in the Tokara Islands should be clarified in future work.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session III: September 1st (15:10-15:30) Around Amami Daiichi Kaikyu (28˚36.9’N, 128˚37.2’E), significant gas plume was observed on the ocean bottom by water column image. At the same position and immediately after the image analysis, CTDCMS hydrocasts were carried out. Strong signal of hydrothermal activity was identified at about 300 m deep by the high turbidity and low pH values even though apparent temperature anomaly was not detected. Large 3He value of up to 50% was observed together with methane content anomaly in the seawater sample, suggestion its strong mantle signature. Based on the depth profile of 3He values, it is possible to calculate helium-3 flux in the region. In addition, origin of the methane is discussed using the CH4/3He ratio and 13C values. In Ko-Takara Shima region (29˚12.3’N, 129˚18.8’E), another significant gas plume was observed at shallower depth of about 100 m with small turbidity and pH anomalies. There is a negative correlation between the pH and 3He values and a positive one between the turbidity and 3He values. At the depth between 90 m and 130 m, 3He values increase with the depth increase, which may provide the information on helium-3 flux in the region. At Wakamiko submarine crater (31˚40.1’N, 130˚45.7’E) located in Kagoshima bay, gas plume signature was again found. There are apparent pH and 3He anomalies below 100 m, while turbidity value is not correlated with pH and 3He values. Depth profile of 3He values is consistent with those in literature (Roulleau et al., 2013), suggesting that a large helium-3 flux is continuing.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A002

Imaging Three-Dimensional Seismic Velocities for Hydrate-Bearing Sediments near Yuan-An Ridge, Off Southwest Taiwan Win-Bin Cheng Department of Environment and Property Management, Jinwen University of Science and Technology, Taiwan [email protected]

Shiao-Shan Lin National Central University, Taiwan

T. Y. Shih and Tan-Kin Wang National Taiwan Ocean University, Taiwan

Char-Shine Liu National Taiwan University, Taiwan

Song-Chuen Chen and Yunshuen Wang Central Geological Survey, Taiwan ABSTRACT This paper presents results of a seismic tomography experiment carried out on the accretionary margin off southwest Taiwan. In the experiment, a seismic air gun survey was recorded on an array of 30 ocean bottom seismometers (OBS) deployed in the study area. The locations of the OBSs were determined to high accuracy by an inversion based on the shot traveltimes. A three-dimensional tomographic inversion was then carried out to determine the velocity structure for the survey area. The inversion indicates a relatively high P wave velocity (Vp) beneath topographic ridges which represent a series of thrust-cored anticlines develop in the accretionary wedge. In addition, data from S-waves generated by P-S conversion on reflection from airgun shots recorded along four lines of ocean bottom seismometers were used also to construct S-wave (Vs) velocity model of hydrate-bearing sediment layers. The inversion indicates a relatively high P-wave velocity beneath topographic ridges which represent a series of thrust-cored anticlines develop in the accretionary wedge. S-wave velocities of the sediments over the entire section, down to >400 m below seafloor, range from 320 to 570 ms-1. We suggested the lateral variation in Vp/Vs profiles in the hydrate-affected zones may be related to the migration conduit of gas-rich fluid and a characteristic of hydrate content. We model Vp using equations based on a modification of Wood’s equation to estimate the gas hydrate saturation. The hydrate saturation varies from 5% at the top ~200 m below the seafloor to 10-15% of pore space close to the BSR in the survey area.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A002

INTRODUCTION At the southwestern Taiwan continental margin, a 4-km-thick sediment column overlying the subducting Eurasian plate is accreted to the Philippine Sea plate and deformed by a series of folds and thrusts (e.g., Lin et al., 2003). BSRs are widely recognized in seismic profiles in this region and their total distribution area is about 2,000 km2 (Liu et al., 2006). This BSR distribution is highly heterogeneous and 70% of them are recognized at well-developed present accretionary prism. Most accreted sediments are coarse terrestrial clastics which are derived from Taiwan mountain belt. In order to understand regional structures, the deposition environment, characteristics of gas-hydrate bearing sediment, and to estimate the amount of gas hydrate for the region, a multidisciplinary research project "Geological Exploration of Gas Hydrate Prospects Offshore of Southwestern Taiwan – Geophysical Investigation" was initiated since 2004. For this purpose, MCS and three-dimensional ocean bottom seismometer (OBS) refraction surveys were conducted during a cruise with the R/V Research I in 2008 (Figs. 1).

Fig. 1: Shaded relief map and the seismic ship tracks (blue lines) off southwest Taiwan. Open triangles indicate relocated ocean bottom seismometers (OBS). Thick yellow lines are seismic sections shown in their respective figures represented by the numbers alongside the lines. R4.1 and R5.2 are topographic ridges (Lin et al. 2008). Three OBS stations (solid triangles) around the R5.2 were not be used in inversion due to sensor decoupling. The bathymetric contour interval is 100 m. DATA ANALYSIS The Jive3D tomographic inversion code was applied to the travel time data set in this study. The inversion program uses a linear inverse theory to estimate the formal uncertainties of velocity and depth parameters using the diagonal elements of the inverse of the Hessian matrix (Hobro et al. 2003). We also image the velocity structure of the sediments and thereby estimate gas hydrate saturations using P-S converted waves. To simplify the process and reduce uncertainty, we chose to use only converted waves from boundaries with large changes in physical property across sediments, e.g. seismic unconformity and BSR. Swave velocities were derived using the optimal Vp model and varying Poisson’s ratio for each layer to obtain the best-fit between the calculated and observed travel times using Rayinvr software (Zelt and Smith, 1992). We can use the resultant seismic velocities to elucidate the accumulation process of gas hydrates in the survey area. From the distribution of seismic property beneath seafloor, obtained with one or more modeling techniques, the concentrations of gas hydrate in the sediments were defined using effective medium-based method (Lee et al. 1996; Helgerud et at, 1999). 27

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A002

RESULTS AND DISCUSSION

Fig. 2 (left): Final P-wave velocities are shown in map view at six slices at the seabed, at 50-m intervals below the seabed and immediately above the BSR. Velocity contour interval is 0.02 km/s. OBS positions are marked as in Fig. 1. Fig. 3 (right):Hydrate saturation inferred for the vertical slices of profiles 4 to 15, using an approach based on a modification of Wood’s equation (Kumar et al., 2007). Color scale marks the estimate hydrate saturation inverted from Vp and Vp/Vs of our velocity model.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A002

CONCLUSIONS (1) P-wave velocity results are integrated with the three-dimensional tomographic inversion of a joint OBS wide-angle reflection and refraction and MCS reflection experiment conducted in 2008 (Cheng et al. 2010), the bottom-simulating reflectors (BSR) closely follows the seafloor and lies at 325 ± 25 m below the seafloor in the region in between the topographic ridges R4.1 and R5.1. (2) BSR is distributed continuously in survey area. However, BSR is discontinuous beneath the topographic ridges which have relatively higher velocities at the same depth than the slope basin sediments. (3) The hydrate-affected zones above the BSR are imaged by lower anomalies in Vp/Vs values, from values of 3.12 to 3.18. (4) We inverted Vp with our three-dimensional velocity model, and estimated gas hydrate saturations in the survey area. The estimated hydrate saturation increase from ~5% at 200 m beneath the seafloor to 10-15% of the pore space in the vicinity of the BSR. (5) The eastward termination of Unconformities may be related to the vertical fluid migration paths. Seismic blanking, push-down effects and loss of high frequencies indicate the reflection pattern of vertical fluid migration paths extending down to more than 2.6 s two-way travel-time. (6) This study improves our knowledge of the velocity structure of gas hydrate in shallow marine sediments, and provides a basis for an improved assessment of the saturation of gas hydrate in the offshore area of southwestern Taiwan. REFERENCES Cheng, W. -B., S. S. Lin, T. K. Wang, C. S. Lee, C. S. Liu, 2010, Velocity structure and gas hydrate saturation estimation on active margin off SW Taiwan inferred from seismic tomography, Marine Geophys. Res., 31, 77-87. Helgerud, M.B., Dvorkin, J., Nur A., Sakai A. and Collett T., 1999, Elastic-wave velocity in marine sediments with gas hydrates: Effective medium modeling, Geophys. Res. Lett. 26, 2021–2024. Hobro, J.W.D., Singh, S.C. and Minshull, T.A., 2003, Three-dimensional tomographic inversion of combined reflection and refraction seismic traveltime data, Geophys. J. Int. 152, 79-93. Kumar, D., Sen, M. K., and Bangs, N. L., 2007, Gas hydrate concentration and characteristics within Hydrate Ridge inferred from multicomponent seismic reflection data, J. Geophys. Res., 112, B12306, doi:10.1029/2007JB004993. Lee, M. W., Hutchinson, D.R., Collet, T.S. and Dillon, W.P., 1996, Seismic velocities for hydrate-bearing sediments using weighted equation, J. Geophys. Res. 101, 20,347-20,359. Lin, A.T., Watts, A.B., Hesselbo, S.P., 2003, Cenozoic stratigraphy and subsidence history of the South China Sea margin in the Taiwan region, Basin Res., 15 (4), 453–478. Liu, C. S., Schnurle, P., Wang, Y., Chung, S. H., Chen, S. C., Hsiuan, T. H., 2006, Distribution and characters of gas hydrate offshore of southwestern Taiwan, Terr. Atmos. Ocean. Sci. 17, 615-644. Zelt, C. A., and R. B. Smith, 1992, Seismic traveltime inversion for 2-D crustal velocity structure: Geophysical Journal International, 108, 16–34.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A004

Analyses of Microbial Diversities and Functions in Potential Gas Hydrate Bearing Area at Offshore Southwestern Taiwan: by Metagenomic Approach Sheng-Chung Chen and Mei-Chin Lai Department of Life Sciences, National Chung-Hsing University, Taichung 402, Taiwan [email protected], [email protected]

Saulwood Lin Institute of Oceanography, National Taiwan University, Taipei 106, Taiwan [email protected] ABSTRACT Gas hydrate is a high potentially alternative energy resource. Due to the interest in marine gas hydrate, the intensive investigations at offshore SW Taiwan, including Bottom Simulating Reflector distribution, high methane and dissolved sulfide concentration, high sulfate reduction rate, shallow depth of sulfate-methaneinterface and carbon isotope composition of the authigenic carbonates, indicated this area is the high potential gas hydrate bearing region. In order to further investigate the microbial community structure and potential functions of methane-based gas hydrate bearing deep sub-seafloor, six DNA samples from top, middle and bottom of two gravity cores, which were obtained from the potential gas hydrate bearing area (G1 station) around Formosa Ridge and control normal area (G2 station) during the OR3-1672 cruise on March 28-30 of 2013, were extracted for metagenomic analyses. Total 1322 archaeal and 9809 bacterial 16S rDNA sequence reads were extracted from six metagenomic datasets and classified based on SILVA taxonomy. Bacterial dominant phylotypes in all datasets are Chloroflexi, Planctomycetes, Deltaproteobacteria and Gammaproteobacteria. The bacterial phylotypes with significantly different occurrences between two areas is the unknown phylotypes of Candidate division JS1 and OD1. In the archaeal part, relative abundance of archaeal 16S rDNA reads in each dataset is 9.02% to 16.05%. Dominant archaeal phylotypes are Deep Sea Hydrothermal Vent Group 6 (DSHVG-6, under Order of Halobacteriales), Marine Benthic Group D/ Deep Sea Hydrothermal Vent Group 1 (MBG-D/DHVEG-1, under Order of Thermoplasmatales), and Thaumarchaeota phylotypes of Group C3, MBG-B and Marine Group I (MGI). In addition, the gas hydrate related phylotypes of ANaerobic MEthane oxidizer (ANME)-2 and ANME-3 have been detected in the bottom of G1 core. Furthermore, the Candidate division JS1 phylotype, which is often associated with gas hydrate bearing sediments and may play important roles in sulfate-methane interface, showed the significant occurrence in the bottom of G1 core. Both phenomena indicated that the bottom of G1 core may be the region of sulfate-methane interface. In addition, functional genes related with methane metabolism were surveyed in this study. Although no methyl-coenzyme M reductase gene (mcr), the key enzyme of methanogenesis, has been found in all datasets, methane metabolism related genes including heterodisulfide reductase genes (hdr) and trimethyltransferase genes (mtt) were found in some datasets. Also environmental stress response genes, e.g., chaperones, were investigated and those genes were widely spread in all datasets. Taken together, the metagenomic analysis could give us the better and more detail understanding of microbial diversity and potential biogeochemical functions without specific spectra or bias of universal primers of these ecosystems. KEYWORDS Gas hydrate, Archaea, Microbial community, Metagenomics 30

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A009

The Genetic Type and Accumulation Characteristics of Biogas in the Guan Tian area of South-Western Taiwan In-Tian Lin, Ching-Tse Chang, Jun-Chin Shen Exploration and Development Research Institute, Chinese Petroleum Corporation, No. 1, Ta Yuan, Wen-Sheng Li, Miaoli 360, Taiwan [email protected]

Tsanyao Frank Yang Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan ABSTRACT Biogas is produced by the metabolism of (anaerobic) bacteria that generate methane in an anaerobic environment. Large accumulations have been found in the Guan-Tian area. It is usually stored in shallow, immature to low-maturity sediments. Biogas plays a part in the Earth’s carbon cycle: 80%~90% of methane in the atmosphere is generated by biogas. The world’s large biogas fields mainly date from the Cretaceous to the Quaternary periods. Biogas fields generally accumulate at depths of several tens to one thousand meters. The studies are based on the gas components of samples that were taken from four wells in the Guan-Tian area. Their contents were mainly methane – up to 97.0% ~ 98.8% - with a few containing ethane and nitrogen. Additionally, the isotope δ13CH4 contained between -64.29‰ ~ -64.47 ‰. From these geochemical characteristics it is adduced that these are primary biogases. Moreover, as the ratio of 3He/4He (Ra) lies in the range 0.06-0.22 it indicates the presence of helium that originated in the earth’s crust - similar to that found in many mud volcanoes in south-western Taiwan. For exploration and production in the Guan-Tian area, the Methanogenesis simulation method is used to evaluate biogas accumulation. As the Erhchuangchi and Kanhsialiao formations have a geothermal gradient below 70℃and a unit yield of 16 mole/m3, it is estimated that primary biogas accumulation in both formations amounts to several hundreds of millions of cubic meters. KEYWORDS Genetic Type; Guan-Tian basin; Primary biogas; Methanogenesis simulation

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A010

Fluid Sources, Intensities, and Biogeochemical Processes of an Active Cold Seep from the Northern South China Sea: Initial Results of Manned Submersible Jiaolong Dong Feng and Duofu Chen Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China [email protected], [email protected]

ABSTRACT Site F (or Formosa Ridge, 22°06.922N; 119°17.130E; 1120 m water depth) represents the only known active seep on the northern South China Sea (SCS). During Dayang 31 cruise in summer 2013, manned submersible Jiaolong dives enabled detailed sampling of the authigenic carbonates and live and dead bathymodiolid mussels from flank to summit of the ridge. Based on mineralogical, stable isotope, and geochronological analyses, this study aims at exploring the origin of the seep fluid and the key biogeochemical processes at the site. Carbonate rocks occurred as fractured blocks, nodules, and nodular masses incorporated in carbonate breccias. The carbonates were comprised mainly of high-Mg-calcite and aragonite. The stable carbon isotope composition (δ13C) of authigenic carbonate varied from 55.38‰ to 34.3‰ (mean: 48.5‰; n=47) vs. VPDB, suggesting methane is the dominant carbon source fuels the system. Oxygen isotopes (δ18O) varied from +1.9‰ to +4.8‰ (mean: +3.9‰; n=47). The observed 18O-enrichement in relation to calculated equilibrium values in the carbonates probably reflects decomposition of gas hydrates. Combination of seafloor observations and the obtained AMS 14C ages suggest that 1) initiation of methane seepage from at least 10.6 ka ago; 2) environmental conditions must have been favorable for enhanced fluid seepage around 6 ka BP and 3) relatively low intensity of seepage from 2 ka BP till today. Factors governing seep activity at this site is not clear. It is speculated that thermally induced destabilization of the local gas hydrate reservoirs that enhanced the seepage activity. Authigenic carbonates from seeps are the unique archives of past seepage and associated environmental parameters. In contrast, using stable isotope compositions of seep mussel tissues could provide detailed information on the biogeochemical processes that was happening at the time of sample collection. Two species of bathymodiolin mussels were observed during the cruise. Bathymodiolus platifrons was common, this specie harbor methanotrophic symbionts while the other rarely observed specie B. aduloides harbor thiotrophic symbionts in their gills. B. platifrons had tissue δ13C values from -77.6‰ to -64.8‰（mean: -70.2‰, n=48, VPDB), reflecting the δ13C values of the seeping methane. The δ13C values of B. aduloides ranged from -37.4‰ to -33.0‰ (mean: -34.2‰, n=12), this values corresponds to the δ13C values of local dissolved inorganic carbon. The δ34S values of B. platifrons and B. aduloides were from 4‰ to 10.5‰ (mean: 6.5‰, n=48, V-CDT) and from -12.9‰ to -4.2‰ (mean: -8.7‰, n=12), respectively. The tissue isotopes clearly indicate that besides the ubiquitous occurrence of anaerobic oxidation of methane (AOM), oxidation of hydrogen sulfide produced during AOM cannot be neglected.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A010

Paired measurement of chemical and isotope compositions in seep carbonate and seep animals would provide valuable insight into the fluid sources, intensities, and biogeochemical process at cold seeps. These proposed analyses would help to build a more complete picture of hydrocarbon seep carbon and sulfur cycling. ACKNOWLEDGMENTS We thank crews of Xiangyanghong 09 as well as the Jiaolong team in helping us meet our scientific objectives during the cruises. Prof. H.Y Zhou (Tongji University) was the chief scientist of the cruise. The research was partially supported by the “Hundred Talents Program” of CAS, NSF of China (Grants: 91228206 and 41373085).

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A011

Molecular Fossils Reveal Biogeochemical Process at an Active Methane Seep from the Northern South China Sea Hongxiang Guan and Nengyou W. Guangzhou Center for Gas Hydrate Research, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, China, [email protected]

Dong Feng and Duofu Chen Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China, [email protected], [email protected] ABSTRACT Anaerobic oxidation of methane (AOM) at cold seeps often leads to formation of authigenic carbonates close to the seafloor. The AOM is conjointly operated by consortia of anaerobic methane-oxidizing archaea (ANME) and sulfate-reducing bacteria (SRB). The composition of AOM communities has been found to vary in response to environmental conditions including flux of methane and sulfate availability, these parameters, on the other hand, affect the mineral composition of the associated carbonates. Thus, a correlation between the composition of AOM communities and carbonate minerals is expected. Lipid biomarkers and their stable carbon isotope compositions among carbonate samples that are dominated by aragonite (sample Bio-1), highMg calcite (HMC; sample Bio-9), and a mixture of aragonite and HMC (samples Bio-4 and Bio-13) from Site F (or Formosa Ridge, 22°06.922N; 119°17.130E; 1120 m water depth), an active cold seep from the northern South China Sea (SCS) have been examined. This study aims to examine the relationship between mineral formation conditions and the AOM communities involved. High contents of lipid biomarkers diagnostic for archaea (δ13C values as low as -133‰ VPDB) and SRB (δ13C values as low as -119‰) were found. Crocetane, characteristic lipid biomarker of ANME-2 archaea, accounts for 67% of hydrocarbons and with sn2-hydroxyarchaeol/archaeol about 2.9, suggesting the prevailing of ANEM-2/DSS during the precipitation of Bio-1. A mixture of ANME-2/DSS and ANME-1/DSS consortia were found in Bio-4 and Bio-13 and predominated by ANME-2/DSS. Interestingly, Bio-9 had extremely low (< 1%) concentrations of AOMassociated lipid biomarkers and no preservation of crocetane. Long-chain n-alkanes contributed with 6% of the hydrocarbon fraction in Bio-1. In contrast, high content of long-chain compounds in hydrocarbons in Bio-4 and Bio-13 indicates that a considerable amount of allochthonous sources contributed to the carbonates. The longchain n-alkanes account for 62% of hydrocarbons in Bio-9. Taking the favored environments for specific AOM consortia and formation conditions for aragonite and calcite together, the factors selecting for specific AOM communities appear to be constrained by the methane flux. If applied with caution, this supposed relationship can be used as a first approximation of methane seepage intensity.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A012

Time-Lapse Seismic Study of Active Gas Seepage at the Arctic Vestnesa Ridge, Southern Fram Strait Sandra Hurter, Stefan Bünz, Andreia Plaza-Faverola and Jürgen Mienert CAGE - Centre for Arctic Gas Hydrate, Environment, and Climate, UiT - The Arctic University of Norway, Department of Geology, Dramsveien 201, N-9037 Tromsø, Norway [email protected]

ABSTRACT The Vestnesa Ridge is a ~100 km elongated sediment drift located on young (< 20 Ma) oceanic crust in the Fram Strait, the only deep-water gateway to the Arctic Ocean. The Vestnesa Ridge sediment drift hosts one of the northernmost oceanic gas hydrate provinces and its proximity of a mid-oceanic ridge makes it unique on the Earth’s ocean floor. Pockmarks occur along the crest of the Vestnesa Ridge, at water depth of 1200-1300 m, but are absent on the flanks of the ridge and on the adjacent western Svalbard continental margin slope. Flares in the water column, detected by single-beam echo sounder system during an R/V Helmer Hanssen cruise in 2012, indicate active seepage of gas from several of these seabed pockmarks to the ocean. High-resolution P-Cable 3D seismic data acquired the same year show sub-seabed vertical fluid flow features connected to the seabed pockmarks. The vertical fluid flow features extend down to the free-gas zone underneath a bottom-simulating reflector (BSR). Above the BSR the presence of gas hydrate is known based on seabed sampling. Below the BSR, these chimneys connect to fault systems, possible pathways to the deeper subsurface. For a time-lapse seismic study of the temporal evolution of gas hydrate and fluid flow systems at the Vestnesa Ridge, we repeated 3D seismic surveys over several years, in order to better constrain the potential dynamics of fluid migration and the gas hydrate stability zone and to reconstruct potential gas migration velocities along the chimneys. Here, we describe seismic acquisition and processing methods used and present preliminary results of our 4D analysis.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A015

Connectivity of the Chemosynthetic Squat Lobster Shinkaia crosnieri (Crustacea: Decapoda: Galatheidae) Between the Cold Seep and Hydrothermal Vent Habitats in the Northwest Pacific Chien-Hui Yang and Tin-Yam Chan Institute of Marine Biology, National Taiwan Ocean University, Taiwan [email protected], [email protected]

Shinji Tsuchida, Katsunori Fujikura, Yoshihiro Fujiwara and Masaru Kawato Japan Agency of Marine Science and Technology, 2-15 Natsushima-cho, Yokosuka, Kanagawa, 237-0061, Japan [email protected] ABSTRACT The deep-sea squat lobster Shinkaia crosnieri, previously only known from hydrothermal vents in the Okinawa Trough, is recently found also from cold seeps off southwestern Taiwan. Preliminary molecular genetic analysis on the mitochondrial COI gene reveals that the vent and cold seep populations form separate clades with 2.4-3.8% divergence. Nevertheless, there is no genetic distinction on the nuclear adenine nucleotide translocase (ANT) intron gene. The result indicates that S. crosnieri from vents and cold seeps may represent distinct populations. More samples as well as more genetic markers will be necessary to confirm this interpretation. INTRODUCTION The deep-sea squat lobster Shinkaia crosnieri is an unique crustacean previously only reported from active deep-sea hydrothermal vents in the Okinawa Trough and Bismark Archipleago, though the record of the latter locality is doubtful. Recently this species is also found from the deep-sea cold seep sites off southwestern Taiwan. Molecular genetic technique is used to investigate the connectivity between the cold seep and hydrothermal vent S. crosnieri populations located at the two sides of Taiwan (i.e. southwestern against northeastern coasts). The genetic markers used are the mitochondrial COI gene barcoding segment and the nuclear adenine nucleotide translocase (ANT) intron gene.

Fig. 1: Shinkaia crosnieri from the Formosa Ridge cold seep site off southwestern Taiwan.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A015

65

S. crosnieri_649-13 S. crosnieri_649-30

S. crosnieri_649-8 S. crosnieri_649-11 S. crosnieri_649-23 S. crosnieri_649-25 S. crosnieri_649-1 S. crosnieri_649-7 S. crosnieri_649-20

S. crosnieri_649-29 77

S. crosnieri_649-18 54 68

S. crosnieri_649-12 S. crosnieri_649-19

S. crosnieri_649-2 S. crosnieri_2 63

Cold seep

S. crosnieri_4 S. crosnieri_5 S. crosnieri_649-14

S. crosnieri_1 S. crosnieri_649-9 S. crosnieri_649-5 S. crosnieri_3 S. crosnieri_649-21 S. crosnieri_649-27 S. crosnieri_649-3 S. crosnieri_649-26 S. crosnieri_649-4 S. crosnieri_649-22 100

S. crosnieri_6 S. crosnieri_7 60

S. crosnieri_649-6 S. crosnieri_649-28 62

S. crosnieri (EU420129) S. crosnieri _9

100 96

S. crosnieri _8 S. crosnieri _10

Hydrothermal vent

0.0020

Fig. 2: Neighbor-joining (NJ) tree from mitochondrial COI barcoding gene (657 bp) for Shinkaia crosineri from hydrothermal vent (n=4) and cold seep (n=37). CONCLUSIONS The preliminary molecular genetic analysis reveals that the vent and cold seep populations form two clades in the mitochondrial COI gene with 2.4-3.8% divergence, though there is no genetic distinction on the nuclear ANT gene. This indicates that S. crosnieri from vents and cold seeps may represent distinct populations. As the present analysis only includes limited individuals from the vents (4 in the COI analysis and 2 in the ANT analysis) and cold seep (37 in the COI analysis and 12 in the ANT analysis), more samples and more genetic markers will be necessary to confirm this interpretation.

REFERENCES Baba, K., A.B. Williams (1998), New Galatheoidea (Crustacea, Decapoda, Anomura) from hydrothermal systems in the West Pacific Ocean: Bismarck Archipelago and Okinawa Trough. Zoosystema, 20, 143156. Baba, K., E. Macpherson, C.-W. Lin, and T.Y. Chan (2009), Crustacean Fauna of Taiwan: Squat Lobsters (Chirostylidae and Galatheidae), National Taiwan Ocean University, Keelung, Taiwan. Chan, T.Y., D.-A. Lee, and C.-S. Lee (2000), “The First Deep-Sea Hydrothermal Animal Reported from Taiwan: Shinkaia crosnieri Baba and Williams, 1998 (Crustacea: Decapoda: Galatheidae),” Bulletin of Marine Science, 67(2), 799-804. Desbruyeres, D., M. Segonzac, M. Bright (2006), Handbook of deep-sea hydrothermal vent fauna, Linz: Biologiezentrum der Oberosterreichische Landesmuseen.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A016

Slope Analysis of a Submarine Landslide near the SW Xiaoliuqiu Huai-Houh Hsu Department of Civil Engineering, Chienkuo Technology University, Taiwan [email protected]

Jia-Jyun Dong and Che-Ming Yang Graduate Institute of Applied Geology, National Central University, Taiwan [email protected], [email protected]

Shu-Kun Hsu Department of Earth Sciences, National Central University, Taiwan [email protected] Win-Bin Cheng Department of Environment and Property Management, Jinwen University of Science and Technology, Taiwan [email protected]

ABSTRACT The characteristics of marine sediments provide important parameters in assessing seabed slope stability. These strength parameters mainly obtained from laboratory triaxial tests. Occurred in the offshore of SW Taiwan on 26 December 2006 with a magnitude of 7.0, the Pingtung earthquake had triggered numbers of submarine landslides (Hsu et al., 2008). This event provides an excellent opportunity to incorporate the back analysis approach to evaluate the representative in situ strength. In this study, two chirp sonar images of the seabed near the SW Xiaoliuqiu before (OR1-809, 29 Step. 2006) and after (OR1-820B, 8 Jan. 2008) the Pingtung earthquake are adopted to identify the location of sliding surface. It is indicated that the studied landslide resulted in a circular sliding surface. The dimensions of the landslide body are 330m in length and a maximum thickness of 30m. Utilizing the widely used software for slope stability (SLIDE 5.0; limit equilibrium method), the strength parameters under the critical condition (i.e. safety factor = 1) can be back calculated. The input parameters included unit weight (ϒ=17 kN/m3, the sediments sampled near the landslide site) and seismic coefficient for pseudo-static analysis (kh=0.067, and kv=0.033) related to the Pingtung earthquake (Central Weather Bureau, Rec. No. 95107). The results indicate that the effective friction angle (ϕ’) of the sliding surface is 14∘ with a cohesion (c’) of 6 kPa. These evaluated strength parameters are close to the results obtained from the isotropically consolidated undrained triaxial (CIU) tests (ϕ’=15.3o , c’=19.4 kPa). According to the infinite slope stability theory, the landslide with a thickness of 30m yields an undrained shear strength (C u) of 37kPa under the critical condition.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A017

Population and Reproduction of the Mussel Bathymodiolus platifrons from Seeps in Southwestern Taiwan Chia-Hsien Chao and Chih-Chien Chang Department of Oceanography, National Sun Yat-sen University, Taiwan [email protected], [email protected] Mei-Chin Lai Department of Life Sciences, National Chung Hsing University, Taiwan [email protected] Saulwood Lin Institute of Oceanography, National Taiwan University, Taiwan [email protected] Li-Lian Liu Department of Oceanography and Asia-Pacific Ocean Research Center, National Sun Yat-sen University, Taiwan [email protected] ABSTRACT In this study, the mussel of Bathymodiolus platifrons from southwestern Taiwan were studied and compared with those from Sagami Bay, Japan. A total of 112 individuals of B. platifrons were collected from Formosa Ridge, southwestern Taiwan in April, 2013 at depth of 1079–1145m. Shell length of the mussels ranged from 31.2 to 119.4mm, with 39% having parasitic polychaete, Branchipolynoe sp. The relationship between shell height (SH) and shell width (SW) in Taiwan and Japan were SW = 0.82SH - 0.18 (N=112; R² = 0.86; **p<0.001) and SW = 0.8SH + 1.0 (N=37; R² = 0.95; **p<0.001), respectively. Histological sections on gonad indicated that B. platifrons is a dioecious species. The condition index (CI), minimum mature size and gamete maturity were further examined. INTRODUCTION The genus of Bathymodiolus within the family of Mytilidae consist species entirely living at hydrothermal vent and cold seep environments. Among them, populations of Bathymodiolus platifrons Hashimoto & Okutani, 1994 has been recorded in cold seeps in Sagami Bay and hydrothermal vents in the Okinawa Trough (Hashimoto and Okutani, 1994; Okutani et al., 2003). The distribution of this species ranges from 644 to 3600m (Hashimoto and Okutani, 1994; Okutani et al., 2003; Sasaki et al., 2005). The occurrence of this species also has been reported by Lin et al. (2007) at Formosa Ridge, southwest of Taiwan. MATERIALS samples of B. platifrons from 3 sites, i.e. 39-2, 42-2 and 50-2, within 1km in distance were collected from Formosa Ridge, southwestern Taiwan in April, 2013 at depth of 1079 – 1145m (from 119o17.125’E and 22o6.929’N to 119o17.146’E and 22o6.962’N).

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A017

RESULTS AND DISCUSSION B. platifrons SH = 0.45SL + 4.93 (N=112; R² = 0.95; **p<0.001; this study) SH = 0.53SL + 0.40 (N=37; R² = 0.97; **p<0.001; Sagami Bay by Okutani et al., 2003) SW = 0.82SH - 0.18 (N=112; R² = 0.86; **p<0.001; this study) SW = 0.8SH + 1.0 (N=37; R² = 0.95; **p<0.001; Sagami Bay by Okutani et al., 2003) (a)

(b)

Bathymodiolus platifrons. (a) Female ovary; (b) male testis.

Based on the results, it is concluded that the mussel B. platifrons is a dioecious species. REFERENCES Hashimoto, J. and T. Okutani (1994), “Four new mytilid mussels associated with deep sea chemosynthetic communities around Japan,” Venus, 53, 61-83. Lin, S., Y. Lim, C.-S. Liu, T. F. Yang, Y.-G. Chen, H. Machiyama, W. Soh, K. Fujikura (2007), “Formosa Ridge, A cold seep with densely populated chemosynthetic community in the passive margin, southwest of Taiwan,” Geochimica et Cosmochimica Acta, 71, A582 Suppl. Okutani, T., K. Fujikura and T. Sasaki (2003), “Two new species of Bathymodiolus (Bivalvia: Mytilidae) from methane seeps on the Kuroshima Knoll off the Yaeyama Islands, southwestern Japan,” Venus, 62, 97110. Sasaki, T., T. Okutani and K. Fujikura (2005), “Molluscs from hydrothermal vents and cold seeps in Japan: A review of taxa recorded in twenty recent years (1984-2004),” Venus, 64, 87-133.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A018

Petrographic and Geochemical Characterization of Cold Seep Carbonate in the Kuohsing Area, Taiwan Qinxian Wang, Chiyue Huang, Duofu Chen Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, China [email protected], [email protected], [email protected]

ABSTRACT Authigenic carbonate has been identified in Miocene marine mudstone succession exposed along the Wushi River near Kuohsing Town, Taiwan. The carbonate deposits collected here are pipe-like structures, mainly composed of dolomite and calcite with abundant terrestrial clasts. The δ13C values of the seep carbonate as low as -44.9‰ VPDB indicate that biogenic methane was the predominant carbon source during the precipitation of seep carbonate. The cold seep carbonate is characterized by slight enrichments of middle rare earth elements and no negative Ce anomalies. This finding suggests that the carbonate was deposited in relatively anoxic environment. ACKNOWLEDGEMENTS This study was partially supported by the National Natural Science Foundation of China (91228206).

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A027

Geochemical Research of Gas hydrate in the northern South China Sea Daidai Wu and Nengyou Wu Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou, China; [email protected], [email protected] ABSTRACT The South China Sea (SCS) is located at the junction of three tectonic plates: the Eurasian, the Pacific and the Indian-Australian. The northern continental slope of the SCS is characterized of the typical passive continental margin in which there developed several oil and gas bearing basins, namely the Qiongdongnan Basin (Southeast Hainan Basin), Pearl River Mouth Basin and Taixinan Basin (Southwest Taiwan Basin) from the southwest to the northeast. The occurrence of gas hydrate in the northern SCS has been confirmed by geological, geophysical and geochemical indicators. Shallow sediment sampling and analysis showed geochemical anomalies revealed the gas hydrates in the South China Sea, i.e., the head-space gas in the sediment, carbon isotopes of methane, Cl–, SO42–profiles, the concentrations of Ca2+, Mg2+, Sr2+, Ba2+, Mg2+/Ca2+ , Sr2+/Ca2+ ratios of the pore waters from sediments, authigenic minerals from sediments. The sulfate-methane interface (SMI) is an important biogeochemical indication for the area with high methane flux and gas hydrate occurrence. The geochemical analysis of pore water from sediments in Dongsha Area shows that the methane flux of upward diffusion in sediments can be controlled sulfate changes gradients of pore water and sulfate methane interface (SMI) depth in sediment, therefore, the change characteristic of sulfate and methane concentration above or below the SMI depth can be used to indicate methane flux below SMI in sediments, and determine the possibility of underlying gas hydrate occurrence. 37 surface cores were collected in the Dongsha Area and the change characteristics of SO42–and H2S concentrations of the pore water and CH4concentration of the headspaces in the sediments were analysed. The results show that the SMI depth is shallower which distributed in range of about 10m in the Haiyang-4 sedimentary body, and the SO42-, H2S and CH4 concentrations abnormity indicates the sulfate reduction zone exists in the surface sediments caused by methane leakage in the Jiulong Methane Reef, which indicates the SMI depth is shallow about 5m below the seafloor. Previous studies show that the methane flux is 2.7 × 10 -3mM / (cm2 • a) in 1244 site of ODP ship, and 0.8 ~ 1.8 × 10-3 mmol / (cm2 • a) in sites of the Black Ridge (Borowski et al., 1996; Borowski et al., 1999). The results of methane flux in Dongsha Area (3.8 ~ 5.9 × 10-3 mmol / (cm2 • a)) are consistent with the these studies, and slightly higher than in the Shenhu Area (2.0 ~ 2.6 × 10-3 mmol / (cm2 • a)), the northern South China (Yang et al., 2010). Two gas hydrate drilling expeditions have been done in the SCS according to the geological, geophysical and geochemical abnormities. The first Chinese gas hydrate expedition (GMGS1) was completed in the Shenhu Area in 2007, and there were 3 gas hydrate bearing sites (SH2, SH3 and SH7). The sulfate methane interaction (SMI) depths were determined according to the pore water concentration profiles of SO42–and CH4 varied from 17 to 27 mbsf. The gas hydrate saturation is calculated from the porewater freshening and its max is up to 25%, 48% and 44% (v/v), respectively at SH3, SH2 and SH7. Methane trapped in the drilling-confirmed Shenhu hydrate deposit is approximately 16 billion m3 (Zhang et al., 2007). The second Chinese gas hydrate expedition (GMGS2) was completed in the Dongsha Area, in the eastern part of the Pearl River Mouth Basin in 2013, and there were 9 gas hydrate bearing sites. The GMGS2 drilled region is a very active area of methane flux, and gas hydrate is common in the first 200 meters below the seafloor (Zhang et al., 2014). 42

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A027 The GMGS-1 & GMGS-2 drilling expeditions help us to better understand the gas hydrate system in Shenhu Area and Dongsha Area in the SCS, and the geochemical data show that gas sources of hydrates are biogenic methane in both areas. However, there are more studies on the geochemical characteristics, distribution features and resource of gas hydrates need to be done in the northern SCS. KEYWORDS Gas Hydrate, the South China Sea, Geochemical indicator, Resource estimate ACKNOWLEDGMENTS This study is financially supported by the National Natural Science Foundation of China (No. 41003010) and (No. 41273022). REFERENCES Zhang, H. Q., Yang, S. X., Wu, N. Y., et al. (2007), Successful and surprising results for China’s first gas hydrate drilling expedition. Fire in the Ice, Methane Hydrate Newsletter, (6-9): 1-5. Zhang, G. X., Yang, S. X., Zhang, M., et al.(2014), GMGS2 Expedition Investigates Rich and Complex Gas Hydrate Environment in the South China Sea. Fire in the Ice, Methane Hydrate Newsletter, 14(1): 1-5. Yang, T., Jiang, S., Ge, L., et al.(2010), Geochemical characteristics of pore water in shallow sediments from Shenhu area of South China Sea and their significance for gas hydrate occurrence. Chinese Science Bulletin. 55(8): 752-760. Borowski, W. S., Paull, C. K., Ussler, Ⅲ W. (1996), Marine pore water sulfate profiles indicate in situ methane flux from underlying gas hydrate. Geology, 24: 655~658. Borowski, W. S., Paull, C. K., Ussler, Ⅲ W. (1999), Global and local variations of interstitial sulfate gradients in deep-water, continental margin sediments: sensitivity to underlying methane and gas hydrate. Mar. Geol., 159: 131~154.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A028

Biogenic/Sub-Biogenic Gas Resource Potential and Gas Hydrate Accumulation in the Pearl River Mouth Basin of the Northern South China Sea Shuhong Wang and Wen Yan CAS Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China [email protected], [email protected]

Jiaxiong He and Wei Zhang CAS Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China [email protected], [email protected]

Zhenquan Lu Institute of Mineral Resources Chinese Academy of Geological Sciences, Beijing 100037, China [email protected]

ABSTRACT The continental marginal basins of the northern South China Sea (SCS) have abundant natural gas resource. Not only a large amount of mature and highly mature coal-formed gas in the shallow and middle-deep strata, but also a large number of biogenic/sub-biogenic gas and their gas reservoirs that independently formed have also been found in shallow layers of the Pearl River Mouth Basin (PRMB) of northern SCS (Pang et al., 2006; He et al.,2008). In this study, the geological and geochemical characteristics of biogenic/sub-biogenic gas and the distribution feature of hydrocarbon source rocks in the Neogene and Quaternary are intensively studied, and the generating capacity and resources of biogenic/sub-biogenic gas also have been predicted based on a large number of gas geochemistry data (Pang et al., 2006; He et al., 2008, 2009) (Fig.1) obtained from gas exploration in recent years and the hydrocarbon accumulation geological conditions. The results show that the biogenic/subbiogenic gas resources are very abundant in this area. Most of the biogenic gas exist in the form of water-soluble gas which mainly displayed in gas drilling measure, but can also be output in the form of free gas to form enriched biogenic/sub-biogenic gas reservoir. The hydrocarbon source rocks of biogenic/sub-biogenic gas in this area are widely distributed, especially the Miocene-Pliocene neritic and bathyal argillaceous source rocks with relatively high abundance of organic matter, where the large hydrocarbon potential can provide adequate gas supply for shallow gas hydrate formed in deep water. Based on the geochemical analysis of the genetic types of deepwater gas hydrate in northern SCS (Gong et al., 2009; Lei et al.,20009; Su et al., 2010, 2011) and the geochemical characteristics of the gas hydrate in other regions of the world (Kvenvolden, 1995; Hachikubo et al., 2010; Vaular et al., 2010), the gas hydrates currently found in this area was further confirmed to be the “self-source diffusion” biogenic hydrate, and their gas source is a mixture gas dominated by biogenic/subbiogenic gas formed in the Organic-rich mudstone from the original area and nearby in deepwater seabed, showing a accumulation model of “self-source diffusion” in which gas source came from original place and nearby and was characterized by near-source migration and accumulation, with a huge resource potential.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A028

Fig. 1 The carbon isotope of methane and the dry coefficient of biogenic/sub-biogenic gas from PRMB REFERENCES Gong, Y.H., S.X. Yang, H.B. Wang, J.Q. Liang, Y.Q. Guo, S.G. Wu, G.H. Liu (2009), “Gas hydrate reservoir characteristics of shenhu area, north slope of the South China Sea,” Geoscience, 23(2), 210-216 (in Chinese with English abstract). Hachikubo, A., A. Krylov, H. Sakagami, H. Minami, Y. Nunokawa, H. Shoji, T. Matveeva, Y. K. Jin, A. Obzhirov (2010), “Isotopic composition of gas hydrates in subsurface sediments from offshore Sakhalin Island, Sea of Okhotsk,” Geo-Marine Letters, 30(3), 313-319. He, J.X., Y.H. Zhu, S.H. Chen, S.S. Cui, W.H. Ma (2009), “Genetic types and mineralization characteristics of gas hydrate and resources potential of northern South China Sea,” Natural Gas Geoscience, 20(2), 237243 (in Chinese with English abstract). He, J.X., Y.J. Yao, H.L. Liu, Z.F. Wan (2008), “Genetic types of natural gas and characteristic of the gas source composition in marginal basins of the northern South China Sea.” Geology in China, 35(5), 1007-1016 (in Chinese with English abstract). Kvenvolden, K.A. (1995), “A review of geochemistry of methane in nature gas hydrate,” Organic Geochemistry, 23(11/12), 997-1008. Lei, X.M., G.X. Zhang, Y. Zheng (2009), “The formation and geological factors of distribution of gas hydrate in the Shenhu area, the northern South China Sea,” Marine Geology Letters, 25(5), 1-9 (in Chinese with English abstract). Pang, X., C.M. Chen, M. Zhu, M. He, J. Shen, B.J. Liu (2006), “A discussion about hydrocarbon accumulation conditions in Baiyun Deep-water Area, the northern continental slope, South China Sea,”. China Offshore Oil and Gas, 18(3), 145-149 (in Chinese with English abstract). Su, P.B., H.Y. Lei, J.Q. Liang, Z.B. Sha, S.Y. Fu, Y.H. Gong (2010), “Characteristics of gas source in the waters of Shenhu and their significance to gas hydrate accumulation,” Natural Gas Industry, 30(10), 103-108 (in Chinese with English abstract). Su, P.B., J.Q. Liang, Z.B. Sha, S.Y. Fu, H.Y. Lei, Y.H. Gong (2011), “Dynamic simulation of gas hydrate reservoirs in the Shenhu area, the northern South China Sea,” Acta petrolei Sinica, 32(2), 226-233 (in Chinese with English abstract). Vaular, E. N., T. Barth, H. Haflidason (2010), “The geochemical characteristics of the hydrate-bound gases from the Nyegga pockmark field, Norwegian Sea,” Organic Geochemistry, 41(5), 437-444. 45

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A029

Seabed Features in the Gas Hydrate Potential Area of the Yung-An and Good Weather Ridges, Off Southwest Taiwan Song-Chuen Chen Central Geological Survey, Ministry of Economic Affairs, Taiwan [email protected]

Shu-Kun Hsu Department of Earth Sciences, National Central University, Taiwan [email protected]

Yunshuen Wang, San-Hsiung Chung, Po-Chun Chen Central Geological Survey, Ministry of Economic Affairs, Taiwan [email protected], [email protected], [email protected]

Ching-Hui Tsai, Hsiao-shan Lin Department of Earth Sciences, National Central University, Taiwan [email protected], [email protected]

Char-Shine Liu, Saulwood Lin and Ho-Han Hsu Institute of Oceanography, National Taiwan University, Taiwan [email protected], [email protected], [email protected]

ABSTRACT The Yung-An and the Good Weather ridges area off SW Taiwan is characterized by a wide BSR distribution on the basis of MCS profiles. High methane fluxes in cored sediments, chemosynthetic communities and authigenic carbonates have been observed in the seabed, suggesting enormous gas hydrate may exist beneath the seafloor. Thrust faults and anticlinal ridges are the main geological structures. Slope basins have also developed in the study area. The thrusts and fractures are the main conduits for fluid migration from deep to shallow strata. We have conducted deep-towed sidescan sonar and sub-bottom profiler surveys to understand the related seabed features in the area. We found gas seeps, pockmarks, pingoes, mud volcanoes, mass-transport deposits (MTDs) and structural lineaments distributed in the study area. The development of gas seeps, pockmarks and mud volcanoes indicates a large amount of methane-rich fluid expulsion. The lineaments could be minor faults or outcrops of bedding plane, providing efficient conduits for fluid migration upward to the seafloor. The high-porosity MTDs in the slope basins are ideal places for gas hydrate formation. In addition, the pingoes could be the gas hydrate mounds. We suggest that the active fluid activity, enormous amount of gas hydrate may exist beneath the seafloor and the near surface gas hydrate may also exist in the study area.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A029 INTRODUCTION The offshore area of the southwest Taiwan belongs to an accretionary wedge setting caused by the NWSE convergence between the Eurasian Plate and the Philippine Sea Plate. The area of the Yung-An Ridge and the Good Weather Ridge is located between the Kaoping and Penghu canyons off SW Taiwan, where the water depths range from 600 m to 1,600 m. The study area is characterized by a series of troughs and anticlinal ridges because of active thrusting and folding. The thrusts and fractures provide efficient conduits for fluid migration from deep to shallow strata in the study area. BSRs are widely distributed in the Yung-An and Good Weather ridges area. In addition, the high methane fluxes, gas plumes and chemosynthetic communities have been observed in the study area based on cored sediments, EK500 sonar and seafloor photos taken by Tow-Cam system, respectively. It indicates that the potential existence of gas hydrate in the study area. In order to understand the related seabed features, we have conducted deep-towed surveys of sidescan sonar and subbottom profiler in the Yung-An and Good Weather ridges area. In this study, we use the deep-towed data to better understand the seabed features in the gas hydrate potential area of the Yung-An and Good Weather ridges. THE RESULTS OF INVESTIGATIONS As the results, we found gas seeps, pockmarks, pingoes, mud volcanoes, mass-transport deposits (MTDs) and structural lineaments are distributed in the study area (Fig. 1). Gas seeps are distributed in the north part of the study area. The fluid conduits of gas seeps are clearly observed in sub-bottom profiles. Pockmarks are widely distributed in the north and south parts of the study area based on sidescan sonar images, indicating active fluid activity. High resistivity anomalies were observed in some pockmarks, implying the gas hydrate or authigenic carbonate were formed in the pockmark area (Hsu et al., 2013). Identified from sidescan sonar images, pingoes are only located in the south part of the study area. They could be gas hydrate or authigenic carbonate mounds (Paul et al., 2007; Hovland and Svensen, 2006). Based the sub-bottom profiles, MTDs are widely distributed in the slope basins in the west of the Yung-An Ridge or between the Yung-An and Good Weather ridges, implying the slumping events sometimes occur at the flank of the ridge. The MTD is an ideal place for the gas hydrate formation due to its high porosity character. Lineaments are observed in the platform and slope basin near the toe of the west flank of the Good Weather Ridge. In general, the lineaments are oriented NNW-SSE, almost parallel to the thrusts. The lineaments could be minor faults or outcrops of bedding plane based on the subbottom profiles. Mud volcanoes are found in the southeastern flank of the Good Weather Ridge. The diameter of crater is ~67 m; the edifice is ~20 m high and the diameter at base is ~300 m. CONCLUSIONS The thrusts, fractures and lineaments are efficient conduits for fluid migration from deep to shallow strata in the study area. The MTD is characterized by a high porosity which facilitates the formation of gas hydrate in the sedimentary layer. In addition, we found many gas venting structures (gas seeps, pockmark and mud volcanoes) distributed in the slope basins, indicating the strong fluid activity in the area. At gas venting sites, the increasing thermal flux at the fluid migration paths makes the bottom of gas hydrate stability zone shallower, thus more methane can be transported outwards than that can be consumed by the anaerobic oxidation of methane (AOM) in subsurface sediment. The increasing thermal, gas and fluid flux create favorable conditions for gas hydrate formation near the seafloor (Poort et al., 2007). The pingoes could be gas hydrate mounds on the seafloor. Meanwhile, the soupy structure was observed in the giant piston core (depth of 5-8 m) MD3277 (25 m long) (Lin, 2010). We suggest that the enormous amount of gas hydrate may exist beneath the seafloor and the near surface gas hydrate may also exist in the study area. 47

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A029

Fig. 1: The geological structures and seabed features in the Yung-An and the Good Weather ridges area.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A029 REFERENCES Hovland, M., and H. Svensen (2006), “Submarine pingoes: Indicators of shallow gas hydrates in a pockmark at Nyegga, Norwegian Sea,” Marine Geology, 228, 15-23. Hsu, S.-K., C.-W. Chiang, R.L. Evans, C.-S. Chen, S.-D. Chiu, Y.-F. Ma, S.-C. Chen, C.-H.Tsai, S.-S. Lin, and Y. Wang (2013), “Marine controlled source electromagnetic method used for the gas hydrate investigation in the offshore area of SW Taiwan,” Journal of Asian Earth Sciences. http://dx.doi.org/10.1016/j.jseaes.2013.12.001. Lin, A.T. (2010), Investigation and Evaluation of Gas Hydrate Resource Potential in the Offshore Area of Southwestern Taiwan : Seismic and Heat Flow Studies – structural and sedimentary characters of hydrate bearing sedimentary layers, report no. 99-25-F, Central Geological Survey, MOEA, Taiwan. Paull, C.K., W. Ussler III, S.R. Dallimore, S.M. Blasco, T.D. Lorenson, H. Melling, B.E. Medioli, F.M. Nixon, and F.A. McLaughlin (2007), “Origin of pingo-like features on the Beaufort Sea shelf and their possible relationship to decomposing methane gas hydrates,” Geophysical Research Letters, 34, L01603. Poort, J., V. Kaulio, D. Depreiter, and V. Soloviev (2007), “The thermal signals in gas hydrate seeps and mud volcanoes: an overview,” In: Tsunemoto H, Shoji H. Yamashita S. editor, Gas Hydrates for the Future Energy and Environment, Proceedings of the 2nd International Workshop on Gas Hydrate Studies and Other Related Topics-for the Future Energy and Enivornment Considerations, Kitami Institute of Technology, Japan, 11-16.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A069

Helium Isotopes of Fluids from Submarine Volcanoes in the South-Okinawa Trough Li-Hsin Kao, Tsanyao Frank Yang, Hsin-Yi Wen and Ai-Ti Chen Department of Geosciences, National Taiwan University, Taiwan [email protected], [email protected], [email protected], [email protected],

Hsiao-Fen Lee Institute of Earth Sciences, Academia Sinica [email protected]

ABSTRACT Many active submarine volcanoes have been found in southern Okinawa Trough. Water column samples from the hydrothermal plumes above venting volcanoes were collected during the OR2-1897 and -1984 cruises. Meanwhile, diving at shallower depths were conducted several times to collect the water samples near the venting sites. In total, 122 water samples from various depths in the offshore area of NE Taiwan were collected for dissolved gases and helium isotopes measurement. The dissolved gases of water column samples show that the CO2 concentration and the alkalinity increase with depth and become higher at the bottom, while the result of O2 concentration shows a reverse pattern. The 3 He/4He ratios near the vicinity of active Kueishantao volcano show highest value, up to 5.5 RA, where RA is the atmospheric ratios of 1.39 x 10-6. The plot of 3He/4He and 3He/20Ne ratios suggests that there may be different sources in this region. Furthermore, we will estimate the helium flux from the venting volcanoes in this area.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session I: September 1st (15:50-16:30)-GIMS12A076

Gas Geochemistry Characteristics of Hydrothermal Fluids from the southwestern Okinawa Trough Hsin-Yi Wen, Tsanyao Frank Yang, Li-Hsin Kao Department of Geosciences, National Taiwan University, Taipei, Taiwan [email protected], [email protected], [email protected]

Hsiao-Fen Lee Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan, ROC [email protected]

Yuji Sano, Naoto Takahata Atmosphere and Ocean Research Institute, The University of Tokyo, Japan [email protected], [email protected]

Shinsuke Kawagucci Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061 Japan Precambrian Ecosystem Laboratory, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa, Japan Submarine Resources Research Project, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa, Japan [email protected]

ABSTRACT Okinawa Trough is a backarc basin of Ryukyu arc-trench system, which extends from SW Kyushu to NE Taiwan. The active volcanic islet lied at the southernmost part of Okinawa Trough and NE offshore Taiwan, called Kueishantao. There are many submarine hydrothermal systems around this area. In this study, we have measured the helium, argon and nitrogen isotopes of two bubble gas samples from Kueishantao and three gas samples extracted from hydrothermal fluids, which collected from Hatoma, Yonaguni knoll IV and Irabu hydrothermal fields during the KY14-02 cruise. The 3He/4He ratios of those samples vary from 4.9 RA to 7.8 RA (where RA is 3He/4He ratios in air), implies a typical subduction signature. The helium isotopic ratios of the sample from Irabu might be a mixing between MORB-type and crust-type helium, and the others consistent with a mixing between MORB-type helium and air-saturated water. The 40Ar/36Ar ratios fall in the range from 280.4 to 307.1, which is similar with the values of atmospheric air. The nitrogen isotopic ratios are heavier than air with δ15N ratios between 1.2 ‰ and 3.8 ‰. Combining with the results of δ15N and N2/36Ar data, we can estimate the contributions based on three-component mixing model, from subducted sediment, atmosphere and mantle components, 27-56%, 41-66% and 2-14%, respectively. KEYWORDS helium, hydrothermal fluid geochemistry, Okinawa Trough, Kueishantao

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IV: September 2nd (08:30-09:10) Keynote speech

Taiwan Gas Hydrate Investigation Program: Present Status and Future Prospective Char-Shine Liu1, Andrew Lin2, Tsanyao Yang3, Saulwood Lin1, Shu-Kun Hsu2, Yunshuen Wang4, San-Hsiung Chung4, Song-Chuen Chen4, Po-Chun Chen4 and the Taiwan Gas Hydrate Investigation Team 1

Institute of Oceanography, National Taiwan University, Taiwan, [email protected] 2 Department of Earth Sciences, National Central University, Taiwan 3 Department of Geosciences, National Taiwan University, Taiwan 4 Central Geological Survey, Ministry of Economic Affairs, Taiwan

ABSTRACT

The area offshore of southwestern Taiwan provides a favorable environment for gas hydrate accumulation. Extensive marine geophysical, geochemical, and geological survey results from the gas hydrate investigation program of the Central Geological Survey, Ministry of Economic Affairs since 2004, reveal that gas hydrates are widely distributed beneath the seafloor offshore of southwestern Taiwan, from the passive margin of the South China Sea continental slope to the submarine Taiwan accretionary wedge. The gas in-place is estimated to be around 2.7 trillion cubic meters. Based on different tectonic settings and geological environments, we can divide the gas hydrate present area into 6 provinces, 2 in the passive margin domain and 4 in the accretionary wedge domain, each with their distinct gas hydrate petroleum systems, play types and prospects. The occurrences of gas hydrates can be categorized into leakage type and combined structural and stratigraphic type. The leakage type is usually associated with gas seepages on top of active mud diapirs, faults that cut across the seafloor, and vertical venting features cutting across sediment strata. Gas hydrates in the combined structural and stratigraphic type are distributed in porous turbidite sands and foraminifer oozes. Various investigation techniques have been used to investigate the distribution and to characterize the gas hydrate reservoirs in recent years. Large-offset multichannel seismic reflection profiling and ocean bottom seismometer observations were conducted over many of the gas hydrate prospects to provide better images of the deeper crustal structures and velocity information. Pseudo 3-D seismic survey and P-cable high-resolution 3-D seismic survey results provide detail images of structural and stratigraphic features as well as fluid migration paths of the gas hydrate prospects. Seismic attribute analyses help to better define the gas hydrate reservoirs and free gas distribution. Giant piston coring cruise using the R/V Marion Dufresne and conventional coring surveys conducted by the R/Vs Ocean Researcher I and V provide seafloor sediment and fluid samples for geological and geochemical analyses. Results from those analyses show that major gas is methane with very few ethane and carbon dioxide, indicating gas hydrates are mostly biogenic in origin. However, some gas samples from active margin exhibit heavier carbon isotopic compositions, implying that there are also thermogenic gas sources in the region. Other high-resolution seafloor surveys, such as deep-towed side-scan sonar and chirp sonar surveys, deep-towed camera images, and ROV and AUV surveys, have discovered active seafloor mud volcanoes and vents, chemosynthetic communities, and carbonate crusts, all indicative of widespread active methane venting systems in the region.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IV: September 2nd (08:30-09:10) Keynote speech

In 2012, the National Energy Program has established a gas hydrate master project to better support and coordinate the Taiwan gas hydrate investigation efforts. International cooperative surveys using advanced survey equipment have been encouraged and emphasized. For example, AUV surveys were conducted in 2012 with MARUM (Germany) and in 2013 with MBARI (USA), P-cable and CSEM surveys were carried out using R/V Sonne in 2013. Sampling tools for Taiwan Ocean Research Institute (TORI) 3000-m depth range ROV have been developed via collaboration with WHOI, USGS and MBARI. More high-resolution 3D seismic (P-cable) surveys, joint AUV-ROV surveys and MeBo shallow seafloor drilling have been planned in the coming years. Eventually, we hope to conduct deep gas hydrate drilling investigation to obtain critical information on gas hydrate studies and to assess the gas hydrate energy resource potentials. In summary, the area offshore southwestern Taiwan provides a unique opportunity to investigate gas hydrate systems in both passive and active tectonic settings, as well as in different geological environments, all close together.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IV: September 2nd (09:10-09:30)

Gas Hydrate Distribution in Channel-Levee Systems of the Danube Deep-Sea Fan (Black Sea) Revealed by New Seismic Data Timo Zander, Jörg Bialas, Christian Berndt, Ingo Klaucke, Dirk Klaeschen, Stephanie Koch, Cord Papenberg and MSM34 Scientific Parties GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstr. 1-3, 24148 Kiel, Gemany [email protected], [email protected], [email protected], [email protected] ABSTRACT The sedimentary succession of the anoxic, deep Black Sea Basin is an ideal location for organic matter preservation and methane gas generation. In the depth range of the gas hydrate stability zone the methane gas will form methane hydrates and large accumulations of gas hydrate probably exist in porous sediments, such as those encountered on the Danube deep-sea fan. Recently collected high-resolution 2D and 3D seismic data, Parasound data, and data from a dense network of ocean-bottom seismometers image the paleo channels of the Danube deep-sea fan in the western Black Sea, which extends from shallow water at the shelf break down to 2000 m water depth. Varying activity of individual channel systems distributed sands along the slope area. As a consequence most of the sandy channel deposits are situated below the zone of gas hydrate stability except for channel-fill deposits. These channel fills may act as migration pathways for gas from the deep parts of the basin into the slope sediments (Lericolais, 2002; Popescu et al., 2006), causing gas hydrate formation in the coarse-grained channel fills.

Fig. 1: Shallow subsurface of the Danube deep-sea fan at the upper limit of the gas hydrate stability zone. The underlying well-stratified sediments below the BSR are characterized by increased amplitudes, indicating high gas content below. A second BSR is observed at about 150 ms below the first one.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IV: September 2nd (09:10-09:30)

A first inspection of the data shows an unexpected rapid deepening of the bottom simulating reflector (BSR) underneath a slump site (Fig. 1), probably indicating that the BSR has not yet reached equilibrium conditions after the slope failure. Failure occurred in water depths of 600 m to 700 m, which is at the updip limit of the hydrate stability zone. Acoustic blanking in Parasound data of the uppermost strata at the BSR outcrop indicates lateral gas migration along the base of the gas hydrate stability zone. Reduced heat flow values and active gas flares at the hanging wall point towards changes in hydrate stability conditions due to the reduced pressure and seawater cooling effects. Another remarkable feature of the Danube deep-sea fan is the presence of multiple BSRs with up to five superposed BSRs within the levee successions. While the uppermost BSR commonly mimics the seafloor at the proposed boundary of gas hydrate stability, the underlying BSRs in places show anomalous dips and fade out in areas below paleo channels. The geological processes that lead to multiple BSRs are still poorly understood. Different BSRs due to different sealevel or bottom water temperatures have been proposed as well as the effect of different gas composition as a cause for this situation. REFERENCES Lericolais, G. (2002), ASSEMBLAGE DELIVERABLE 16 : Report on velocity analysis and on core information about methane release (ASSEssMent of the BLAck Sea sedimentary system since the last Glacial Extreme) Rep., IFREMER, Brest. Popescu, I., De Batist, M., Lericolais, G., Nouzé, H., Poort, J., Panin, N., Versteeg, W., Gillet, H., 2006. Multiple bottom-simulating reflections in the Black Sea: Potential proxies of past climate conditions. Marine Geology 227, 163-176.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IV: September 2nd (09:30-09:50)

Anthropogenic Methane Emissions from Abandoned Oil and Gas Wells in the North Sea- How much Methane is Leaking into the Ocean and finally into the Atmosphere? Lisa Vielstädte, Jens Karstens, Matthias Haeckel, Mark Schmidt, Peter Linke, Susan Reimann, Volker Liebetrau, and Klaus Wallmann GEOMAR, Helmholtz Centre for Ocean Research Kiel, Germany [email protected], [email protected],[email protected], [email protected], [email protected], [email protected], [email protected], [email protected]

Daniel F. McGinnis IGB. Leibniz Institute of Freshwater Ecology and Inland Fisheries, Germany [email protected] ABSTRACT

The North Sea hosts several thousand abandoned wells; many believed to be leaking methane. But just how much of this greenhouse gas is emitted into the water column and ultimately reaches the atmosphere is not known, since there is generally no monitoring mandatory after proper well abandonment (Gasda et al., 2004). Here, we aim to quantify methane leakage from abandoned boreholes in the North Sea. For this purpose, we investigated three abandoned wells in the Norwegian sector of the North Sea, all of which show gas seepage into the bottom water. The isotopic signature of the emanated gas and the minor constituents of higher hydrocarbons, point towards a microbial origin and hence to gas pockets in the sedimentary overburden above the hydrocarbon reservoirs. The shallow origin of the seeping gas is supported by chaotic seismic facieses and high seismic amplitude anomalies in the surface sediments that are indicative of fluid flow and accumulations of gas that the wells were drilled through. In-situ gas flow measurements at the three wells result in total annual CH4 emissions of ~23 tons that are comparable to those at major natural seepage sites such as Tommeliten (Schneider von Deimling et al., 2011). Hence, the three investigated wells are an efficient source for methane into North Sea bottom waters. Nevertheless, bubble-driven atmospheric methane fluxes are small at the studied wells since more than 98% of the gas released at the seabed is dissolved in the 81 to 93 m deep water column before reaching the sea surface. Leaky wells at shallower water depths will be more relevant in terms of atmospheric fluxes. Considering the extensive drilling activity over the past 40 years and given the high density of shallow gas accumulations in the North Sea, leakage from abandoned wells is likely to constitute an important part of the respective regional CH4 budget. In order to assess the total methane flux from abandoned boreholes in the North Sea, we compare the well-paths of ~50 wells with locations of shallow gas pockets that have been identified by bright spots in 3D seismic data in the Norwegian sector of the North Sea. First results indicate that ~ 30% of the abandoned wells were drilled through shallow gas and are thus supposed to be leaking methane. Further extrapolation to the entire area of the North Sea and using simulations with a numerical bubble dissolution model allows us to estimate the resulting anthropogenic methane flux into the ocean and across the sea surface.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IV: September 2nd (09:30-09:50) REFERENCES Gasda, S.E., Bachu, S., Celia, M.A., 2004. Spatial characterization of the location of potentially leaky wells penetrating a deep saline aquifer in a mature sedimentary basin. Environmental Geology 46, 707-720 Schneider von Deimling, J., Rehder, G., Greinert, J., McGinnis, D.F., Boetius, A., Linke, P., 2011. Quantification of seep-related methane gas emissions at Tommeliten, North Sea. Continental Shelf Res. 31, 867-878.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IV: September 2nd (09:50-10:10)

Development of Abyss Twisted-Pair Imaging System and Autonomous Benthic Lander for Gas Hydrate Exploration Chau-Chang Wang, Hsin-Hung Chen, Yuan-He Lin, Jian-Hong Chen, Chun-Cheng Huang, ChiaMin Lin, Chung-Ray Chu, and Ying-Hsueh Chien Institute of Undersea Technology, National Sun Yat-sen University, Taiwan [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]

Chin-Chang Hung Department of Oceanography, National Sun Yat-sen University, Taiwan [email protected] ABSTRACT Starting from 2012, the gas hydrate was officially announced as one of the main themes of the National Science and Technology Program– Energy (NSTPE) by the National Science Council (NSC) of Taiwan. Either the projects hosted by Central Geological Survey (CGS), or the forerun project of the Gas Hydrate NSTPE, introduced many advanced survey instruments from other international ocean research institutes. Instruments such as Deep-Towed Camera from Woods Hole Oceanographic Institution, Autonomous Underwater Vehicle and TV-guided Grabber from MARUM, served the gas hydrate surveys with good performance. However, these unique instruments or tools are, in general, developed jointly by the scientists and engineers to meet special needs for ocean field experiments. In other words, they are not commercial products supported by private companies. In case of revision or modification of the system is needed, the local scientists will not have as good services as that of commercial products. The objective of this work is to form an engineering team within Taiwan to provide technical support and custom-made development needed by the exploration of Gas Hydrate NSTPE. Two instruments, Abyss Twisted-pair Imaging System (ATIS) and Autonomous Benthic Lander (ABL), were prioritized in the developments at the first stage. ATIS was developed for real-time seafloor observation, especially for locating the gas-hydrate outcrops and the biological/ecological characteristics around the gas hydrate seeps. ATIS, operated via a CTD cable and with its telemetry link, can uplinks sensor data and highdefinition (HD) live video streams up to 1920 by 1080 resolution to the surface vessel in real time through the 8000 m long CTD cable. The diving capability of the ATIS allows it to reach the depth of 3000 m. In all, the ATIS has made 24 dives, 75 km track lines, and 73 hours dive duration off southern-west Taiwan until the end of 2013, in which the deepest dive is 2630 m. In addition to the visual survey, another investigation target is the dissolved organic carbon (DOC) which is a significant product associated with microbial methane consumption. Therefore, the ABL was developed as an instrument platform suitable for water sampling at different heights near the sea floor. The ABL is battery powered, in which an onboard micro control unit (MCU) coordinates the power cycles and the operation of each sampler. The ABL is also equipped with a dual-anchor release mechanism to reduce the possibility of release failure. After the ABL survey is completed, the dual release mechanism is activated to free the ABL from the ballast and the glass floatation lifts the instrument to the sea surface. The prototype of the ABL was built and tested in field trial at the end of 2013. Based on the techniques we have developed in this work, the ATIS and ABL will be extended to integrate several sub-systems, such as chirp sonar sub-bottom profiler or Raman spectrometer. The multi-purpose platform can have co-site measurement of different physical and chemical parameters. This approach provides more reliable evidences of the existence of gas hydrate deposit such that the success of the pilot drilling program can be better ensured. KEYWORDS Gas hydrate, Abyss Twisted-Pair Imaging System, Real-time video, Autonomous Benthic Lander, The south-west waters of Taiwan 58

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session V: September 2nd (10:30-10:50)

Gas Seeps BioGeoChemical Anomalies at Active and Passive Margin of the South China Sea Saulwood Lin, Wan-Yen Cheng, and Chieh-Wei Hsu, Institute of Oceanography, National Taiwan University, Taipei, Taiwan [email protected], [email protected], [email protected]

Tsanyao Frank Yang Department of Geosciences, National Taiwan University, Taipei, Taiwan [email protected]

ABSTRACT Gas flares, shallow SMTZ, high concentrations of methane, reduced sulfide minerals, and large-scale build up of authigenic carbonate were found in areas near gas flares on summits of echelon ridges in the active margin and also on top of some erosional ridges on the passive margin (Lin, 2011, Lin et al., 2006). In addition, BSR were found in areas up to 50% of the Northeastern South China Sea continental margin near Taiwan, which implied abundant gas hydrate at depth (Liu, et al., 2006; Lin et al., 2009). The existence of seeps in both active and margin in the close vicinity provides an excellent setting in studying differences, if any, between the active and passive environments. In this report, we have studied the Formosa Ridge (FR) in the passive margin and the 4WC Ridge (4WCR) in the active margin. Near Sea floor visual survey, coring, and a series of chemical analysis, i.e., pore water sulfate, sulfide, methane, chloride, stable isotopic O18, and sediment carbonate, organic carbon, pyrite, stable isotopic carbon of organic and carbonate, were conducted to better define differences and similarities of gas seep and benthic chemosynthesis communities. Our results show that significant differences existed between seeps at the active and the passive margin. Strong flares were found on top of the FR, weak at the 4WCR, shallow SMTZ (10s cm) vs. deep, large benthic chemocommunites vs. small, as well as types of benthic community. Similarities also were found between the two sets of study environments, e.g., both show conduits from deep strata, carbonate build up, patches of mussel beds, large bacterial mats. Fig. 1A show one dense galathea crab patch on top of the mussel bed at the FR and Fig. 1B the mussel bed on top of 4WCR. Fig. 2A show a large authigenic carbonate build up on FR and Fig. 2B the platy carbonate on the 4WCR. Large scale carbonate build up on surface and pyrite the highest concentration of authigenic minerals in sediments are the two most typical anomalies at seeps of both the active and passive margin. Existence of dense galathea crab patch at the FR differed that at the 4WCR where mussel beds were mostly dominant observed of that chemo-community. Higher concentration of seep methane is the driving mechanism for the observed variations. However, exact nature for the differences require further study.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session V: September 2nd (10:30-10:50)

Fig. 1A. Dense galathea mussel bed on the FR.

Fig. 1B. Dense mussel bed on the 4WCR.

Fig. 2A. Large carbonate build up on top of the FR.

Fig. 2B. Authigenic carbonate on top of the 4WCR.

REFERENCES Lin, C,-C., A. T.-S. Lin, C. S. Liu, G.-Y. Chen, W.-Z. Liao, P. Schnurle (2009), Geological controls on BSR occurrences in the incipient arc-continent collision zone off southwest Taiwan. Mar. Petrol. Geol. 26, 11181131. Liu, C.-S., P. Schnurle, Y. Wang, S.-H. Chuang, Chen, T.-H. Hsiuan (2006) Distribution and characters of gas hydrate offshore of southwestern Taiwan. Terr. Atmos. Ocean. Sci. 17, 615–644. Lin, S., W.-C. Hsieh, Y. C. Lim, T. F. Yang, C. S. Liu, Y. Wang (2006) Methane migration and its influence on sulfate reduction in the Good Weather Ridge region, South China Sea continental margin sediments. Terr. Atmos. Ocean. Sci. 17, 883–902. Lin, S (2011) Summary Reports of Geochemical Studies on the Gas Hydrate as Resource Potential, the Investigation Offshore Southwestern Taiwan. Central Geological Survey Report 100-25, 130 pp.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session V: September 2nd (10:50-11:10)

Methane Gas Flares in the Tatarskyi Strait Boris Baranov, Dar’ya Rukavishnikova P.P.Shirshov Institute of Oceanology, Russian Academy of Sciences Moscow, Russia [email protected]

Young Keun Jin Korean Polar Research Institute, Incheon, Korea [email protected]

Vladimir Prokudin, Alexander Salomatin, Natal’ya Nikolaeva, Alexander Derkachev, Anatoliy Obzhirov V.I.Il’ichev Pacific Oceanological Institute, Far East Branch Russian Academy of Sciences, Vladivostok, Russia [email protected]

Hirotsugu Minami, Hitochi Shoji Environmental Energy Resources Research Center, Kitami Institute of Technology, Japan [email protected]

ABSTRACT The Tatarskyi Strait separates the Primorye district of the Russian Far East and the Sakhalin Island; in the bottom relief it corresponds to the same name trough striking in SW-NE direction. The trough’s depth ranges from 1800 m in the south to less than 300 m in the north. Methane gas flares in the Tatarskyi Trough were first discovered and studied in the frame of international project Sakhalin Slope Gas Hydrates (SSGH) (Operation Report., 2013, 2014). Within the study area gas flares were found only in the north-eastern slope of the Tatarskyi Trough. They appear in the area stretching along the outer shelf and shelf break at a distance of about 80 km. Maximum depth of gas flares occurrence is 340 m in water depth and their heights do not exceed 300 m (Fig.1). The gas flares occurring in the north part of Fig. 1b (gray color zone) spatially coincides with a zone of remarkable relief features that were found within outer shelf and upper slope in depth intervals of 400-250 m. They are represented by elongated V-shaped depressions or cracks. The individual cracks are up to several km long, 500 m wide and 40 m deep. The cracks are stretched sub-parallel to the slope; they are spaced up to several hundred meters apart and may locate in en-echelon pattern (Fig. 2). The cracking zone area extends 40 km long and 5 km width. Cracks disappear southward of the point where slope’s morphology and strike changes (Fig. 1b). Similar cracking structures were found on other continental slopes, for example, on Norwegian continental margin (Mienert et al., 2010; Laberg et al., 2013). Several mechanisms are supposed to explain their genesis; one of them implies that cracks were originated due to gas expulsion caused by the dissociation of gas hydrates. This supposition is confirmed by evidence of gas escape (pockmarks, acoustic masking) in the cracks-containing area; nevertheless no evidence of active fluid escape from seabed cracks in form of gas flares were found there (Mienert et al., 2010). 61

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session V: September 2nd (10:50-11:10)

Fig. 1.Bathymetric maps of the Tatarskyi Trough (a) and its north-eastern slope (b), the locations of the gas flares (reverse triangles) and part of echosounder profile LV62_12 showing gas flares (c). Thick closed line indicates the study area. Grey color area in Fig. 1b marks cracking zone. Location of profile LV62_12 is shown in Fig. 2a. SRTM data and data obtained in SSGH cruises were used for drawing of Figs.1a and 1b, correspondently.

Fig. 2. Bathymetric maps (a, b) of the coring stations (numbered white diamonds) where gas hydrates were retrieved and parts of seismic sections along the profiles LV62_12 (c) and LV62_17 (d). Reverse triangles indicate gas flares; dotted line marks contour of the gas chimneys, lines indicate location of the seismic profiles. Arrows mark edges of seismic lines shown in Fig. 2a and 2b. Contour interval is 5 m.The locations of the maps are shown in Fig.1b.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session V: September 2nd (10:50-11:10) In contrast, active fluid escape from seabed cracks in form of gas flares are observed on the north-eastern slope of the Tatarskyi Trough. It supports a suggestion (Mienert et al., 2010) that cracks origination can be conditioned by hydraulic fracturing caused by increase of pore pressure due to gas hydrates dissociation. Active fluid escape suggests also presence of vertical turbid gas chimneys with horizontal dimension of up to 2.6 km on seismic cross-sections under the clusters of the gas flares (Fig. 2).Three sedimentary cores with gas hydrates were retrieved inside these gas chimneys. Gas flares area and cracking zone correspond well to the depths of around 300 m in water depth where the base of the hydrate stability zone (BHSZ) outcrops (Jin et al., 2010). Thus we can suppose that present day methane release from the seabed to the water column occurs due to gas hydrates dissociation. From other hand reflection seismic data suggest that the gas chimneys extend to deeper depths below the BHSZ. It indicates that gascharged fluids may also originate from deep-seated hydrocarbon reservoirs.

REFERENCES Jin, Y.K., Y.G., Kim, B.Baranov, H.Shoji, and A. Obzhirov (2011), “Distribution and expression of gas seeps in a gas hydrate province of the northeastern Sakhalin continental slope, Sea of Okhotsk,” Marine and Petroleum Geology, 28, 1844-1855. Laberg, J.S., N.J. Baeten, P. Lagstad, M.Forwick, and T.O. Vorren (2013), “Formation of a large submarine crack during the final stage of retrogressive mass wasting on the continental slope offshore northern Norway,” Marine Geology, 346, 73–78. Mienert, J., M. Vanneste, H. Haflidason, and S. Bunz (2010), “Norwegian margin outer shelf cracking: a consequence of climate-induced gas hydrate dissociation?” International Journal of Earth Sciences, 99(1), S207–S225. Operation Report of Sakhalin Slope Gas Hydrate Project 2012, R/V Akademik M. A. Lavrentyev Cruise 59 (2013), Korea Polar Research Institute, Jin Y.K., H. Shoji, A. Obzhirov and B. Baranov, 163. Operation Report of Sakhalin Slope Gas Hydrate Project II, 2013, R/V Akademik M. A. Lavrentyev Cruise 62 (2014), Environmental and Energy Resources Research Center, Kitami University, Shoji, H. Y.K. Jin, B. Baranov, N. Nikolaeva, and A. Obzhirov, 111.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session V: September 2nd (11:10-11:30)

Geochemistry of Gases and Fluids at “MV12” Offshore SW Taiwan Nai-Chen Chen, Tsanyao Frank Yang, Yu-Chun Huang, Hsuan-Wen Chen, Lulu Chen Hong-Chun Li Department of Geosciences, National Taiwan University, Taiwan [email protected], [email protected]

Pei-Ling Wang Institute of Oceanography, National Taiwan University [email protected]

Chin-Chang Hung Department of Oceanography, National Sun Yet-sen University

Chau-Chang Wang Institute of Undersea Technology, National Sun Yet-sen University

ABSTRACT Submarine mud volcanoes play an important role for marine carbon cycle. At least 13 mud volcanoes have been found (Chen, 2011) in offshore SW Taiwan. In this study, we present results of gases and pore waters collected at acoustic chimney site located at MV12. Pore water profiles of sulfate and total alkalinity show that sulfate-methane transition zone (SMTZ) is around 260 cmbsf. That pore fluids are abruptly depleted in chloride, sodium and other major cations indicate that there is an upward fluid. Relative to chloride, pore waters are enriched in sodium and depleted in potassium; D decreasing and 18O increasing with depth. These evidences may imply clay mineral dehydration. Below SMTZ, molecular (C1/C2+ < 40) and isotopic (13C-CH4= -38.2 ‒ 36.0‰) indicators point to a thermogenic dominated gas. At SMTZ, 13C of methane, carbon dioxide and dissolved inorganic carbon show an complicated relationship. It may be associated with anarobic oxidation of mehane (AOM) and the upward fluid. Although there can be back reaction of AOM and methenogenesis near SMTZ, the characteristic of microbial source of methane is still unapparent due to the strong upward fluid. KEYWORDS carbon isotope, AOM, mud volcano, oxygen isotope INTRODUCTION On-land mud volcanoes in Taiwan have been surveyed for more than 10 years. Through the geophysical research, plenty of mud diapirs have been found under offshore SW Taiwan (Chow et al., 2000; Lin et al., 2008, 2009); however, it’s hard to conclude there are submarine mud volcanoes without direct evidence. Recently, with advenced technology, including sidescan sonar, sub-bottom profiler survey (Chen et al., 2010) and remotely operated vehicle (ROV), the amount of studies of submarine mud volcanoes can become more.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session V: September 2nd (11:10-11:30) Submarine mud volcanism are an important pathway for degassing of deeply buried sediments and fluids enriched in hydrocarbons and other elements (e.g., Dimitrov 2002; Etiope and Klusman 2002; Kopf 2002). The chemistry of extrusion of fluids, gases, and sediments provides information of sedimentary diagenetic process because it reflects the interaction with surrounding sediments and rocks. There are lots processes can affect chemistry of pore water, including (1) organic matter degredation (Jørgensen, 1982; Martin et al., 1993; Wallmann et al., 2006), (2) sedimentary mineral precipitation and dissolution (Chan and Kastner, 2000; Dahlmann and de Lange, 2003; Moore et al., 2004; Luff and Wallmann, 2003), (3) interaction with surrounding rock (Vanneste et al., 2011; Reitz et al., 2011; Chao et al., 2013), (4) formation and dissosiation of gas hydate (Saito and Suzuki, 2007; Hiruta et al., 2009). The chemistry of gases can offer other details of dynamic microbial activities at shallow marine sediment (around 200 cmbsf). Combining chemistry of pore water and gas is an important approach for differntiating these processes. In this study, sediment cores were retrieved by piston corer (200 - 800 cm of length) in year 2013 aboard the r-v OR5 (Leg 1309-2) not only from MV12 but also Virgin Ridge (MT7, Fig. 1). Generally, in SW Taiwan, fluids flow through diffusion at lots of area (Chuang et al., 2013); howevre, at submarine mud volcanoes, advection is the major migration. Sediment core taken from Virgin Ridge is for comparison with MV12 because the types of migration are different from these two sites.

Fig. 1: The map of coring sites. 65

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session V: September 2nd (11:10-11:30) RESULTS AND DISCUSSIONS At MT7, Cl- and K+ show no anomoly. Br- and NH4+ increase with depth, and it may be caused by organic matter degradation. Due to carbonate precipitation, Ca2+ and Mg2+ decrease. At MV12, most profiles of cations and anions show concave curves and significant decreasing at around 250 cmbsf. It may indicate an upward fluid here.

Fig. 2: Profiles of cations and anions at site MV12 (circle) and MT7 (triangle). CONCLUSIONS We can have following conclusions: gas profiles at both sites, MV12 and MT7, show obvious 13C-depleted CO2 and DIC, and indicate AOM process. 12C-enriched CH4 appear below SMTZ, it may because of methanogenesis. Methanogen would use lighter DIC and can produce methane with more 12C. From the values of Br/Cl, we find a deep organic carbon source at MV12. Results of d18O and dD of pore water show that fluid from MV12 may be affected by clay minerl dehydration; however, the extent of delpetion of potassium is not obvious. Concentration of lithium and boron may be associated with dehydration of hydrous minerals, and give more information of this upward fluid. REFERENCES Chan L. H. and Kastner M. (2000) Lithium isotopic compositions of pore fluids and sediments in the Costa Rica subduction zone: implications for fluid processes and sediment contribution to the arc volcanoes. Earth Planet. Science Letters 183, 275–290. Chao, H. C., You, C. F., Liu, H. C., Chung, C. H. (2013) The origin and migration of mud volcano fluids in Taiwan: Evidence from hydrogen, oxygen, and strontium isotopic compositions. Geochimica Et Cosmochimica Acta 114, 29–51. Chen, S. C., Hsu, S. K., Tsai, C. H., Ku, C. Y., Yeh, Y. C., Wang, Y. S. (2010) Gas seepage, pockmarks and mud volcanoes in the near shore of SW Taiwan. Marine Geophysical Research 31, 133–147. Chow, J., Lee, J. S., Sun, R., Liu, C. S., Lundberg, N. (2000) Characteristics of the bottom simulating reflectors near mud diapirs: offshore southwestern Taiwan. Geo-Marine Letters 20, 3-9. 66

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session V: September 2nd (11:10-11:30)

Chuang, P. C., Dale, A. W., Wallmann, K., Haeckel, M., Yang, T. F., Chen, N. C., Chen, H. C., Chen, H. W., Lin, S., Sun, C. H., You, C. F., Horng, C. S., Wang, Y. S., Chung, S. H. (2013) Relating sulfate and methane dynamics to geology: Accretionary prism offshore SW Taiwan. Geochemistry Geophysics Geosystems 14, 2513–2545. Dahlmann and de Lange (2003) Fluid-sediment interactions at Eastern Mediterranean mud volcanoes: a stable isotope study from ODP Leg 160. Earth and Planetary Science Letters 212, 3-4, 377-391 Dimitrov L. I. (2002) Mud volcanoes – the most important pathway for degassing deeply buried sediments. Earth-Science Review 59, 49–76. Etiope G. and Klusman R. W. (2002) Geologic emissions of methane to the atmosphere. Chemosphere 49, 777– 789. Hiruta, A., Snyder, G. T., Hitoshi, T., Matsumoto, R. (2009) Geochemical constraints for the formation and dissociation of gas hydrate in an area of high methane flux, eastern margin of the Japan Sea. Earth and Planetary Science Letters 279, 326-339. Jørgensen B. B. (1982) Mineralization of organic matter in the seabed – the role of sulfate reduction. Nature 296, 643–645. Kopf, A. J. (2002) Significance of mud. Reviews of Geophysics 40, 2. Lin, A. T., Liu, C. S., Lin, C. C., Schnurle, P., Chen, G. Y., Liao, W. Z., Teng, L. S., Chuang, H. J., Wu, M. S. (2008) Tectonic features associated with the overriding of an accretionary wedge on top of a rifted continental margin: An example from Taiwan. Marine Geology 255, 186-203 Lin, A. T., Yao, B. C., Hsu, S. K., Liu, C. S., Huang, C. Y. (2009) Tectonic features of the incipient arc-continent collision zone of Taiwan: Implications for seismicity. Tectonophysics 479, 28-42. Luff, R., Wallmann, K. (2003) Fluid flow, methane fluxes, carbonate precipitation and biogeochemical turnover in gas hydrate-bearing sediments at Hydrate Ridge, Cascadia Margin: Numerical modeling and mass balances. Geochimica Et Cosmochimica Acta 67, 3403-3421. Martin, J. B., Gieskes, J. M., Torres, M., Kastner, M. (1993) Bromine and iodine in Peru margin sediments and pore fluids—implications for fluid origins. Geochimica Et Cosmochimica Acta 57, 4377-4389. Moore, T. S., Murray, R. W., Kurtz, A. C., Schrag, D. P. (2004) Anaerobic methane oxidation and the formation of dolomite. Earth and Planetary Science Letters 229, 141-154. Peng, T. R., Wang, C. H., Huang, C. C., Fei, L. Y., Chen, C. T. A., Hwong, J. L. (2010) Stable isotopic characteristic of Taiwan's precipitation: A case study of western Pacific monsoon region. Earth and Planetary Science Letters 289, 357-366. Reitz, A., Pape, T., Haeckel, M., Schmidt, M., Berner, U., Scholz, F., Liebetrau, V., Aloisi, G., Weise, S. M., Wallmann, K. (2011) Sources of fluids and gases expelled at cold seeps offshore Georgia, eastern Black Sea. Geochimica Et Cosmochimica Acta 75, 3250-3268. Saito, H., Suzuki, N. (2007) Terrestrial organic matter controlling gas hydrate formation in the Nankai Trough accretionary prism, offshore Shikoku, Japan. Journal of Geochemical Exploration 95, 88-100. Vanneste, H., Kelly-Gerreyn, B. A., Connelly, D. P., James, R. H., Haeckel, M., Fisher, R. E.,Heeschen, K. (2011) Spatial variation in fluid flow and geochemical fluxes across the sediment-seawater interface at the Carlos Ribeiro mud volcano (Gulf of Cadiz). Geochimica Et Cosmochimica Acta 75, 1124-1144. Wallmann, K., Aloisi, G., Haeckel, M., Obzhirov, A., Pavlova, G., Tishchenko, P. (2006) Kinetics of organic matter degradation, microbial methane generation, and gas hydrate formation in anoxic marine sediments. Geochimica Et Cosmochimica Acta 70, 3905-3927

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session V: September 2nd (11:30-11:50)

The Bremer Canyon Ocean Animal Hotspot: – A Case of Seepage-Induced Congregation? Martin Hovland1 and David Riggs2 1Tech Team Solutions, Stavanger, Norway 2RiggsAustralia, Bremer, SW Australia ABSTRACT In the water column above the 600 – 1000 m deep Bremer Canyon in the Southern Ocean, about 60 km off the shores of SW Australia, there are several anomalous occurrences of various features and animals: Occasionally, there are slicks of oil and ‘dirty’, organic-rich surface water Annual congregations of many types of birds, including the Albatross and schools of fish For ten years, there have been annual congregations of larger animals, such as pods of large orcas (killer whales), sperm whales, and pilot whales; schools of large sharks, and the occasional giant squid. Dave has studied the annual congregation for ten years in succession and found that orcas come to the location not only for feeding, but also for social and vital purposes, such as mating, reproduction and giving birth. The presence of so many large marine predators begs the question: What are the special conditions that attract the animals to this specific location? Although it has not been documented, there are most probably seeps of hydrocarbons and other fluids on the bottom of the Bremer Canyon. The reason for this suspicion is that the oil industry has released data indicating that there are prospects in the area, and also salt diapirs to the seafloor surface. This year’s annual survey confirms that there is very high activity in the area, including the occasional surface oily slicks.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session V: September 2nd (11:50-12:10)

Aerobic Conversion of Methane to Inorganic and Organic Carbon Pools Assessed by Stable Isotope Probing Ruei-Long Guo, Mmeng-Shen Huang and Yu-Shih Lin Department of Oceanography, National Sun Yat-Sen University, Taiwan [email protected], [email protected], [email protected]

Li-Hung Lin and Tsanyao Frank Yang Department of Geosciences, National Taiwan University, Taiwan [email protected], [email protected]

Pei-Ling Wang and Saulwood Lin Institute of Oceanography, National Taiwan University, Taiwan [email protected], [email protected]

ABSTRACT The seafloor offshore southwest Taiwan is characterized by morphological features typical for gas seepage such as mud volcanoes, mussel beds, and carbonate mounds. Elevated concentrations of methane (more than 4 μmol L–1; Chuang et al., 2010) have been frequently detected in the bottom water, yet the fate of methane in seawater is poorly understood. To clarify the kinetics and mechanism of methane conversion to dissolved inorganic carbon (DIC), dissolved organic carbon (DOC) and particulate organic carbon (POC) under oxic conditions, we carried out a stable isotope probing experiment using the materials collected from the Four-Way Closure Ridge in November, 2013. Bottom-water samples collected near a cold seep habitat were inoculated with surface sediment retrieved with a suction sampler mounted on a towcam. The water samples were then incubated in closed containers with a headspace containing air and 13CH4, amended to a final dissolved concentration of 796 μmol L–1. After 37 days of incubation, the stable carbon isotopic (δ13C) values of DIC and POC increased by 25,000‰ and 7,700‰, respectively. The potential aerobic methane oxidation rate was 42 μmol L–1 d–1, which is in the same order of magnitude to aerobic methane oxidation rates in freshwater environments (Guérin and Abril, 2007). The amount of methane-derived POC was about 1% of total added 13 CH4. Our next step is to determine the δ13C values of DOC, and to compare the kinetics of methane conversion to the three distinct carbon pools. REFERENCES Chuang, P.-C., T.F. Yang, W.-L. Hong, S. Lin, C.-H. Sun, A.T.-S. Lin, J.-C. Chen, Y. Wang, and S.-H. Chung (2000), “Estimation of methane flux offshore SW Taiwan and the influence of tectonics on gas hydrate accumulation,” Geofluid, 10, 497–510. Guérin, F., and G. Abril (2007), “Significance of pelagic aerobic methane oxidation in the methane and carbon budgets of a tropical reservoir,” Journal of Geophysical Research - Biogeosciences, 112, doi:10.1029/2006JG000393.

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Methane Fluxes, Gas Hydrate and Oil-gas Deposit in the Okhotsk Sea Anatoly Obzhirov V.I.Il’ichev Pacific Oceanological Institute, 690041, Baltiyskaya St.43, Vladivostok, Russia. E-mail: [email protected] ABSTRACT Gas hydrate in the Okhotsk Sea was taken in the surface sediment of area with methane flux. The first methane flare was found in North-East Sakhalin slope in 1988. In this area in 1991 the present gas hydrate was found in the surface layers of sediment (2-5 m under Sea floor). Since from 1988 to 2013 methane bubbles fluxes (flares) from sediment to water column increased every year and now they were found in the East Sakhalin slope and shelf of Okhotsk Sea more than 500. Methane concentration increased in 100-1000 times as well as in bottom, column and surface water and sediment in area with bubbles. Gas hydrate in surface sediment in Okhotsk Sea was found in the 17 areas. Source of methane is deep layers that contain oil-gas on hydrocarbon deposit. It is very important regularity of relationship between methane fluxes, gas hydrate and oil-gas deposit. Investigation of gas hydrate and other geological characteristic in the Okhotsk Sea was provided in frame international projects from 1998 year. These are Russian-Germany (KOMEX, 1998-2004), Russian-JapanKorea (HAOS, 2003-2006 and SAKHALIN, 2007-2012 and 2013-2017). Thus, complex investigations with international cooperation allow us to discover methane fluxes, gas hydrate and tofind much regularity to form and to destroy gas hydrate in the Okhotsk Sea. There is show that it is present relationship between methane fluxes, gas hydrate and oil-gas deposit.

RESULT OF IVESTIGATION Very important to understand what is gas hydrate and what is relationship to form and to destroy gas hydrate and what is substance around gas hydrate. There is question what is age gas hydrate. When it is forming in the past and present years and what is source of methane to form gas hydrate. If we can answer in these questions we may estimate how many gas hydrate areas and what is volume of hydrocarbon in the gas hydrate. Other question – how gas hydrate influences in the environment. Methane distribution on the Okhotsk Sea were investigated from 1984. The first purpose was to search oil-gas deposit to use gas (especially hydrocarbon) like indicator of oil-gas structures. The first gas hydrate was found in Okhotsk Sea in area with bubbles of methane flux that was gone from sediment to water. The first flux of methane bubbles has been found in water column in 1988 in North-East Sakhalin slope (Obzhirov et. al., 1989) and in this area gas hydrate has been found the same in near surface sediment (depth about 1-5 m below sea floor) in 1991 (Ginsburg et.al., 1993, Gaedicke Ch., et. al.. 1997). After the first discovery of methane flux and gas hydrate field many international expedition were provided in Sakhalin shelf and slope of the Okhotsk Sea to search flux of methane and gas hydrate (Obzhirov, 1993, Obzhirov et.al., 2002, Obzhirov et.al., 2004, Young-Gyun Kim et.al., 2013).

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VI: September 2nd (13:30-13:50) Monitoring investigation of it show that methane fluxes appear in this area in the period seismo-tectonic activity of the west part Okhotsk Sea. It is beginning in 1988-1989 and it is continued today. In zones fault methane goes up from bottom gas hydrate-bearing sediment (BSR). Sources of methane are free gas from deep hydrocarbon bearing layers sediment and destroyed gas hydrate because temperature increased and pressure decreased in zones fault. In the Okhotsk Sea in depth more than 400 m in surface layers of sediment second (young) gas hydrate is formed in areas with methane flux. It is usually like layer 1-3 cm thickness or fragments different morphology (fig. 1). There was found more thickness of the layer of gas hydrate - 34 cm (see fig. 1, Г).

Fig. 1 Cores sediment were sampled gravity pipe. White color layers in the mud sediment are gas hydrate. Gas hydrate layers have different morphology. One layer have thinks 34 cm (see fig.1 Г) and agglomerate of gas hydrate (see fig.1 B)

In East Sakhalin slope of the Okhotsk Sea we found layer sediment in depth 10-12 m under surface sediment with great methane anomaly – 100-200 mM/l, but without gas hydrate. I think it is layer consisted gas hydrate in the past years. In past period the same like now there were seismic activity, methane fluxes and have formed gas hydrate. In our period of investigation including geological, geophysics and hydro-acoustics survey have been found the next regularities: 1 Every year new methane bubbles fluxes (flares) from sediment to water column were found (fig.2a and 2b). In most flare areas, methane concentration in bottom water column (1000-10000 nl/l) and sediment (10100 ml/l) increase up to 100-1000 times as high as background value. All summer of methane flux in Sakhalin shelf and slope of Okhotsk Sea reached to 2013 more than 500 (fig. 3a).

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a

b

Fig.2a Hydroacoustics image of methane babbles flux from sediment to water in the Sakhalin slope of Okhotsk Sea (fig 2a in depth 820 m), and shelf (fig. 2b, depth 175 m). Gas of flux destroy layers of surface sediment (see layers of sediment under flux, fig. 2a). Hydroacoustics image of fluxes wrote of A.Salomatin

a

b

Fig. 3a. The scheme shows a region where detailed gas geochemical investigations have been carried out. Many new flares were found on the Sakhalin North-East slope of the Okhotsk Sea. Red circles indicate flare positions. Fig. 3b Methane distribution in area with flux of methane bubbles (Station 30, bottom water depth is 650 m). Red rhombus are points of water samples to measure methane in stations (St.9 – St. 14) in the North-East Sakhalin shelf and slope of the Okhotsk Sea.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VI: September 2nd (13:30-13:50) 2. Mostly methane fluxes located in the zones fault. It connections with the fellow: 2.1 Sakhalin shelf consist many oil-gas deposits. Thickness of sediment with oil-gas-bearing layers in this area reach 7-9 km and in slope of it thickness of sediment is about 5-6 km. It consist the same oil-gasbearing layers. Methane is going from deep layers to up in surface sediment and water column via zone fault. Source of methane is mostly from oil-gas bearing layers. Isotopic ratio of carbon of the methane бC13 is -55 – 65 %o (.Akihiro Hachikubo et.al., 2010) It is show of mixture microbial and thermogenic sources of methane. But microbial methane is forming to use flux of thermogenic methane from oil-gas deposit. When thermogenic methane come up to surface sediment methane oxidation bacteria destroy CH4 to form ion HCO3- and other bacteria form methane to use ion HCO3- to take light in weight isotopic C12. After it process isotopic ratio of methane бC13 to come to light -55 – 65 %o 2.2 Monitoring investigation showed that activities of methane fluxes were increased during in the period of seismic-tectonic activity in the Sakhalin slope of the Okhotsk Sea. It starts from 1988 and continue now. It regularity supports episodes of earthquakes – 1995-Neftegorsk, 2001-Uglegorsk, 2003-Khokkaido, 2007-Nevel’sk, 2011 Fukusima and other. 2.3 Methane bubbles come up to the sea floor from the depths of the sediment via zone fault. In this area gas hydrate is form in near surface layers sediment in gas hydrate stability zone. Below this zone (bottom gas hydrate thickness, BSR) free gas accumulates. If zone fault activities pass way increase and free gas (mostly methane) come up in surface sediment and water. Methane could form gas hydrate layers in near surface sediment in the gas hydrate stability zone (low temperature and high pressure). 2.4 Methane reach the Sea floor and in cool temperature in it condition a second (new) gas hydrate layers form near Sea floor sediment usually with cm-scaled layer or fragments in the water depth deeper 400 m. A remarkable sample was massive hydrate layer with about 34 cm thickness (see fig.3a). 3. In areas without oil-gas deposit and gas hydrate concentration of methane is background, about 20-30 nl/l in bottom water and 70-80 nl/l in surface water in the Okhotsk Sea. Methane anomalies in bottom water rich 1000- 2000 nl/l and more in area with flux of methane bubbles (fig. 3b). 4. Sea floor in area with methane flux destroyed. In this area hole and hillock are formed like mud volcano. Diameter one of it is about 100-800 m. 5. In sea floor of methane flux area usually appear a new assemblage (many shell and other benthos, crab and fish). In near surface sediment layers carbonate fragment and concretions are formed. CONCLUSION So, methane fluxes and high methane concentration in bottom water are great indicator to search gas hydrate in the sediment of Sea. The increasing quantities of methane flares and methane concentration in water column since 1988 are connected with seismic-tectonic activation of the faults in the Sea of Okhotsk. In other side, in area with methane fluxes morphology of Sea floor is changing (hill and hole appear), structure of chimney is forming in sediment where gas is going up via sediment. In this area in sediment appear shells, carbonate concretions and other mineral association. All geological, geophysical, gas geochemical, hydroacoustic, morphostructure complex are very important indicator to search gas hydrate and to understand regularity to form and to destroy of it (V.Yusupov et. al., patent, 2008, A.Obzhirov, et.al., patent, 2008 ). Thus, complex investigations allow us to discover methane fluxes, gas hydrate and to find much geological regularity around gas hydrate in the Okhotsk Sea as well as to examine relationship between methane fluxes, gas hydrate and oil-gas deposit. It is knowledge help to work out of mining hydrocarbon from gas hydrate (Obzhirov, Tagiltsev, patent, 2010)

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VI: September 2nd (13:30-13:50) REFERENCES Ginsburg G.D., Soloviev V.A., Cranston R.E., Lorenson T.D., Kvenvolden K.A. (1993) Gas hydrates from the continental slope, offshore Sakhalin Island, Okhotsk Sea//Geo-Marine Letters, 13, 41-48. Gaedicke Ch., Baranov B. et. al. (1997) Seismic stratigraphy, BSR distribution and venting of methane –rich fluids west off Paramushir and Onecotan Island, Northern Kurils//Marine Geology, V.116. Akihiro Hachikubo, Alexey Krylov, Hirotoshi Sakagami, Hirotsugu Minami, Yutaka Nunokawa, Hitoshi Shoji, Tatiana Matveeva, Young K. Jin, Anatoly Obzhirov. Isotopic composition of gas hydrates in subsurface sediments from offshore Sakhalin Island, Sea of Okhotsk. Geo-Marine Letters, 2010 г., Том 30, № 3-4, 313-319 Obzhirov A.I., Kazansky B.A., and Melnichenko Yu.I. (1989): Effect of the sound scattering in water of the Okhotsk Sea. // Pacific Geology, N2: 119-121 (in Russian). Obzhirov A.I. (1993): Gas geochemical fields in bottom water of seas and oceans; Science Publ., Moscow: 139 pp. (in Russian). Obzhirov A.I. et .al., (2002) Methane monitoring in the Sea of Okhotsk. Dalnauka, Vladivostok, 250 p. (in Russian). Obzhirov A., Shakirov R., Salyuk A., Suess E., Biebow N., Salomatin A. (2004). Relations between methane venting, geological structure and seismo-tectonics in the Okhotsk Sea//Geo-Marine Letter. Vol. 24 № 3., p. 135–139. Young-Gyun Kim, Sang-Mook Lee, Young Keun Jin, Boris Baranov, Anatoly Obzhirov, Alexander Salomatin, Hitoshi Shoji The stability of gas hydrate field in the northeastern continental slope of Sakhalin Island, Sea of Okhotsk, as inferred from analysis of heat flow data and its implications for slope failures // Marine and Petroleum Geology 45 (2013) 198-207 V.Yusupov, A.Salomatin, A.Obzhirov. Gas-Geophysical complex to search underwater gas hydrate. Patent. RU № 70377 U1, 2008. Bull. No 2. A.Obzhirov, V.Yusupov, A.Salomatin. Gas-Hydroacoustic complex to estimate seismic-tectonic activity. Patent. RU № 78333 U1, 2008. Bull. No 32. A.Obzhirov, A.Tagil’tsev. Technological complex to extract gas from gas hydrate fields of Okhotsk Sea, Patent. 2010. Bull. No 10

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VI: September 2nd (13:50-14:10)

Comparative Methane Cycling and Microbial Communities in Marine and Terrestrial Mud Volcanoes Li-Hung Lin Department of Geosciences, National Taiwan University, Taipei, Taiwan [email protected]

Pei-Ling Wang Institute of Oceanography, National Taiwan University, Taipei, Taiwan [email protected]

Tsanyao F. Yang Department of Geosciences, National Taiwan University, Taipei, Taiwan [email protected]

Yunshuen Wang Central Geological Survey, Ministry of Economic Affairs, Taipei, Taiwan [email protected] ABSTRACT

Methane exerts profound effects on the global warming over geological time. Recent estimates suggest that methane released from mud volcanoes and seepages contributes significantly to the atmospheric methane budget. Of various factors, microbial methane producing (methanogenesis) and consuming (aerobic and anaerobic methane oxidation) processes appear to play a vital role in regulating the exact flux of methane emission. To address how these microbial processes operate under different geochemical contexts in marine and terrestrial realms, and what microbial community assemblages could account for these processes, sediment cores collected from three mud volcanoes offshore and onshore Taiwan were analyzed using geochemical and molecular approaches. The geochemical results indicate a metabolic zonation pattern with anaerobic oxidation of methane (AOM) overlying methanogenesis for most samples investigated. The terminal electron accepting processes potentially coupled to AOM, however, vary upon sites. While sulfate reduction is prevalent in the marine setting and one of the terrestrial sites, ferric and/or manganese reduction dominates over others in another terrestrial site. Aerobic methane oxidation appears to be less significant to the overall methane consumption. The geochemical resemblance and distinction among sites could be also correlated to the variations in community assemblages. In particular, a number of specific bacterial and archaeal lineages are endemic to specific sites. Overall, our results demonstrate that the prevalence distribution of AOM provides an effective biological filtration for the removal of methane produced in situ or migrating from a deep source. Complex assemblages of microbial communities are likely modulated by the geochemical contexts imposed by the subsurface-surface interactions inherited with different mud volcano systems.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VI: September 2nd (14:10-14:30)

Doming and Seepage, Development of shallow Gas Migration Pathways – Opouawe Bank, Offshore New Zealand Stephanie Koch, Joerg Bialas, Matthias Haeckel GEOMAR Helmholtz Centre of Ocean Research Kiel, Wischhofstr. 1-3, 24148 Kiel, Germany [email protected]

Gareth Crutchley GNS Science, 1 Fairway Drive, Avalon 5011, Lower Hutt, New Zealand [email protected]

Cord Papenberg, Dirk Klaeschen GEOMAR Helmholtz Centre of Ocean Research Kiel, Wischhofstr. 1-3, 24148 Kiel, Germany [email protected]

ABSTRACT The migration of gas through marine sediments typically manifests itself as gas chimneys or pipes and can lead to the formation of cold seeps. Seeps are often linked to seafloor features like seabed domes and pockmarks. Seabed domes have been reported from many different places around the world, forming as a result of focused fluid migration reaching the shallow sub-seafloor (Hovland and Judd 1988; Hasiotis et al., 1996; Lee and Cough, 2003; Plassen and Vorren, 2003). They usually appear as unimpressive topographic highs with diameters ranging from 10-1000 m (Hovland and Judd, 1988) and exhibit small vertical displacements and layer thickness in comparison to their width (Boudreau, 2012). The dome-like uplift of the sediments results from an increase in pore pressure caused by gas accumulation in near-seabed sediments. In this context doming is widely discussed to be a precursor of pockmark formation. However, our study demonstrates that doming can also be a preliminary stage in the evolution of active seep sites without pockmark formation. In this contribution, we show that methane migration and accumulation can lead to sediment doming and the subsequent formation of gas seeps. We present high resolution sub-bottom profiler (Parasound), high resolution 2D and 3D multichannel seismic data and geochemical data from Opouawe Bank, an accretionary ridge at the Hikurangi Margin, offshore New Zealand’s North Island. Beneath this bank, methane migrates along stratigraphic pathways (Krabbenhoeft et al., 2013) from a maximum source depth of 1500-2100 mbsf (meter below seafloor) towards active cold seeps at the seafloor, which could be mapped and classified by Dumke et al. (2014). We show that, in the shallow sediment of the upper 100 mbsf, this primary migration mechanism changes into a process of gas accumulation leading to sediment doming and related fracturing of strata above the accumulation zones. This is reflected by the transformation of the gas migration structures from elongated conduits at depth to almost rounded seabed structures in the shallow surface sediment. Our high-resolution data allow for a detailed inspection of the different stages from doming to seafloor seepage and enable us to develop a conceptual model for gas seepage development in the shallow sediment.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VI: September 2nd (14:10-14:30)

Fig. 1: Images of cold seeps related seafloor doming and gas migration pathways.

REFERENCES Boudreau, B.P. (2012), “The physics of bubbles in surficial, soft, cohesive sediments.” Marine and Petroleum Geology, 38, 1–18. Dumke, I., I. Klaucke, C. Berndt, and J. Bialas (2014), “Sidescan backscatter variations of cold seeps on the Hikurangi Margin (New Zealand): indications for different stages in seep development.” Geo-Marine Letters, doi 10.1007/s00367-014-0361-7. Hasiotis, T., G. Papatheodorou, N. Kastanos, and G. Ferentinos (1996), “A pockmark field in the Patras Gulf (Greece) and its activation during the 14/7/93 seismic event.” Marine Geology, 130, 333–344. Krabbenhoeft, A., G.L. Netzeband, J. Bialas, and C. Papenberg (2010), „Episodic methane concentrations at seep sites on the upper slope Opouawe Bank, southern Hikurangi Margin, New Zealand.” Marine Geology, 272, 71-78. Lee, S.H. and S.K. Chough (2003), “Distribution and origin of shallow gas in deep-sea sediments of the Ulleung Basin, East Sea (Sea of Japan).” Geo-Marine Letters, 22, 204-209. Plassen, L. and T.O. Vorren (2003), “Fluid flow features in fjord-fill deposits, Ullsfjorden, North Norway.” Norwegian Journal of Geology, 83, 37-42.

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Activating Mud Volcanism Indicated by 210Pb Geochronology at a Submarine Mud Volcano, Offshore Kaohsiung, Southwestern Taiwan Akihiro Hiruta, Tsanyao Frank Yang, Yi-Jyun Chen, Hsuan-Wen Chen, Nai-Chen Chen, Tsun-Han Yang, Kuo-Yen Wei, Jyh-Jaan Huang and Sheng-Rong Song Department of Geosciences, National Taiwan University, Taiwan [email protected] (present; Meiji University, [email protected]), [email protected]

Chih-Chieh Su and Saulwood Lin Institute of Oceanography, National Taiwan University, Taiwan [email protected], [email protected]

Song-Chuen Chen Central Geological Survey, Ministry of Economic Affairs, Taiwan [email protected] ABSTRACT At a submarine mud volcano named MV12 offshore southwestern Taiwan, gas bubble emission disperses sediment particles into the water column and re-deposition of the particles becomes massive (structureless) zone at a restricted area of the MV12 crest. We applied lead-210 (210Pb) geochronology to the sediments and revealed activating mud volcanism from sediment deposition rate. In a reference core without mud breccia, 210Pb activity decreases with sediment depth. In the massive zone at the MV12 crest, the activity increases with sediment depth. The unusual trend suggests increase in the sedimentation rate. Because the massive zone sediments originate in the gas bubble emission, increased sedimentation rate indicates activated mud volcanism at MV12. INTRODUCTION Taiwan is located at compressional tectonic zone between the Philippine Sea plate and the Eurasian plate. Dozens of terrestrial and submarine mud volcanoes (MVs) are distributed in the south of the Western Foothills which is the second geological province inland from the east, and offshore the coast line of the province (e.g., Chen et al., 2013; Hsu et al., 2013; Liu et al., 1997; Shih, 1967; Yang et al., 2004). Among the thirteen submarine MVs discussed by Chen et al. (2013), MV12 is one of the largest conical structures. Although most of the other MVs in that study (MV1–11) are located above two active mud diapirs, MV12 is found above a ~15-km-long isolated mud diapir (Lin et al. 2009a; Chen et al. 2013). Compared with MV1, which has active mudflow from the crest, the mud volcanism of MV12 is gentler (Chen et al. 2013; Hsu et al. 2013), and the near-seafloor sediments of MV12 probably record transiting mud volcanism. Four sediment cores from the MV12 discerned its eruption history. Radiographs of these cores revealed wide distribution of mud breccia sediments over the MV12 and a restricted distribution of seafloor massive (structureless) zone around a core site on the flat crest. The massive layer above mud breccia zone is characterized by enrichment of coarse silt-sized particles. The size sorting is due to re-deposition of particles dispersed into the water column by bubble emission. In this study, radioactive lead-210 (210Pb) geochronology was applied in order to reveal the rate of particle deposition related with gentle gas bubble emission. For comparison, one reference core outside of another MV was included. 78

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VI: September 2nd (14:30-14:50) CONCLUSIONS In a reference core without mud clasts, 210Pb activity decreases with sediment depth; however, the activity increases with sediment depth in the massive zone at the MV12 seafloor. The unusual trend suggests increased sedimentation rate which depends on amount of particles dispersed into the water column. The unusual 210Pb activity trend indicates re-activated mud volcanism after eruption of mud breccia sediments which distributes below the massive zone.

REFERENCES Chen, S.C., S.K. Hsu, Y. Wang, S.H. Chung, P.C. Chen, C.H. Tsai, C.S. Liu, H.S. Lin, and Y.W. Lee (2013), “Distribution and characters of the mud diapirs and mud volcanoes off southwest Taiwan,” J Asian Earth Sci, In press. Hsu, S.K., S.Y. Wang, Y.C. Liao, T.F. Yang, S. Jan, J.Y. Lin, and S.C. Chen (2013), “Tide-modulated gas emissions and tremors off SW Taiwan,” Earth Planet Sci Lett, 369-370, 98-107. Liu, C.S., I.L. Huang, and L.S. Teng (1997), “Structural features off southwestern Taiwan,” Mar Geol, 137, 305-319. Shih, T.T. (1967), “A survey of the active mud volcanoes in Taiwan and a study of their types and the character of the mud,” Petrol Geol Taiwan, 5, 259-311. Yang, T.F., G.H. Yeh, C.C. Fu, C.C. Wang, T.F. Lan, H.F. Lee, C.H. Chen, V. Walia, and Q.C. Sung (2004), “Composition and exhalation flux of gases from mud volcanoes in Taiwan,” Environ Geol, 46, 1003-1011.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VI: September 2nd (14:50-15:10)

Trophic Structure of Megabenthic Assemblages at Seep and Surrounding Ecosystems in the South China Sea Hsuan-Wien Chen Department of Biological Resources, National Chiayi University, Taiwan, [email protected]

Hsing-Juh Lin Department of Life Science, National Chung Hsing University, Taiwan, [email protected]

Chun-Ming Yeh Department of Life Science, National Chung Hsing University, Taiwan, [email protected] ABSTRACT The biological compositions and trophic relationships of benthic megafauna were investigated at the seep and surrounding ecosystems located in the South China Sea. Based on the samples collected by three survey cruises in 2013, we had recognized more than 60 taxa from over 260 pieces of large benthic animal specimens. Among them, 15 species of fish, 23 species of crustacean, and one species of gastropods were presented, including 4 new records in the area and one potential new species to be described. Additional 20 plus invertebrate taxa remained to be identified with both morphological and molecular characteristics for the better understanding of biological diversity at the seep ecosystems in the South China Sea. Furthermore, stable isotopic measures ( δ 13C , δ 15N ) were taken from tissues of these megabenthos for elucidating the trophic relationships among them. The preliminary results of stable isotope analysis showed two distinct trophic assemblages suggested the use of different food sources. The seep endemic deep-sea bivalve and squat lobsters were apparently consumed chemosynthetic organic carbon derived from seep methane; while the fishes, shrimps and other epibenthic invertebrates were feed with photosynthetic fixed carbon. Within the seep fauna, the stable isotope nitrogen suggested three trophic subgroups. The deep-sea bivalves were major symbiotic chemosynthetic producers. The squat lobsters and the parasitic polychaetes of the bivalves were two primary consumers in this seep ecosystem. The weak trophic links between megafauna of the seep and the surrounding ecosystems inferred by the stable isotopic data remained to be thoroughly examined. Further applications of DNA identification for food content in the megabenthos would verify the observed tropic interaction pattern from our current study.

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Intensity of Hydrocarbon Leakage Reflected by Vertical Successions of Methane-Related Carbonates, Pockmarks and Chimneys; a Study of Fluid Venting Structure in 3D Seismic Data, Offshore Angola Sutieng Ho School of Earth and Ocean Sciences, Cardiff University, United Kingdom Cenozoic Geoscience Editing and Consulting, Australia [email protected]

Patrice Imbert Total-CSTJF, France [email protected]

Joe Cartwright School of Earth and Ocean Sciences, Cardiff University, United Kingdom [email protected]

Jean-Philippe Blouet Department of Geosciences, University of Fribourg, Switzerland [email protected]

ABSTRACT A number of venting structures such as acoustic chimneys, pockmarks and amplitude anomalies are observed in 3-D high-resolution seismic data of Offshore Angola, in a succession of Neogene-Quaternary hemipelagite deposits, above the oil and gas-bearing reservoirs. Positive high amplitude anomalies (PHAAs) (fig. 1) associated with pockmarks or acoustic chimneys have recently started to be studied by seismic interpreters. These PHAAs in the our study area often occur either at the top of acoustic 'pull-up' chimneys (fig. 2) or at pockmark bases (fig. 3) or surrounded the lower part of pockmarks. Their high positive amplitude indicates that they correspond to higher impedance material than the background sediments. Seismic pull-up effects under the PHAAs (fig. 2) show that they correspond to high velocity material. Combined with the local character of the anomalies in the fine-grained clastic environment of the Neogene interval in this basin, PHAAs are interpreted as seep carbonates, possibly associated with gas hydrates in some cases. In addition, a PHAA with negative depression has been drilled through recently. Samples from borehole caving as well logs recorded confirm that PHAA corresponds to hard carbonate. Methanogenic carbonates can form either on the seafloor or in the sulfate methane transition zone (SMTZ), a few tens of meters below at the maximum. Below the surface, they result mostly from anaerobic oxidation of methane (AOM), while on the seafloor they may result from AOM or from the development of chemosynthetic communities. Fluid leakage at the seabed can be indicated directly by chimneys, pockmarks and PHAAs. Among these indicators, only PHAAs are diagnostic of methane gas. The fact that PHAAs form close to or on the seafloor (within the limits of SMTZ) means that their vertical successions reflect their temporal evolutions. The size, number and morphology of the PHAAs are interpreted to reflect the relative quantities of escaped methane. In combination with the presence of pockmarks and chimneys associated with vertical successions of PHAAs on seismic, the dynamics of fluid expulsions and the flux rate variations over time can be determined. 81

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VI: September 2nd (15:10-15:30) The rules used in our interpretation were derived from the framework previously established by other authors. Linear PHAAs without conical pockmarks or circular depressions characterizes relatively slow fluid seeps. They can be succeeded by sub-circular PHAAs and shallow depressions which inferred slow to moderate seeps (fig. 3). Then the seep can become either a fast vent and terminated into a pockmark crater (fig. 3). This succession in time indicates that relatively slow flux rates at the venting site changed lately to faster rates until they reached the eruption threshold and making the final crater (fig. 4). In this study we suggest that the histories of regional fluid flux can be reconstructed by studying the genetic relationship and the spatial-temporal evolution of fluid venting structures.

+ 0 _ Amp

10ms TWT 30m

Figure 1. Seismic wriggles of a positive high amplitude anomaly. Image taken from Ho et al. (2012). 100m

Figure 2. The linear PHAAs are associated with seismic pull-up indicating a "seismic fast material". Image taken from Ho et al. (2012).

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Pockmark 3 crater

-

Initial pockmark crater  fluid eruption Sub-circular PHAA  moderate vent

0 3

2 Linear PHAAs  initially slower vent

2

+ Amp 1

1

400m

Figure 3. A succession records variation of fluid flux. The rate of fluid venting increasing over time is expressed by the stacked-up linear and sub-circular PHAA below a pockmark. Images taken from Ho et al. (2012).

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VI: September 2nd (15:10-15:30)

Ho et al. (2012) Figure 4. A hypothetical combined vertical succession for the evolution of different venting structures, depending on the dynamics of venting. (A) Initiation of seepage. (B) Slow seeps at fault locations are characterized by linear PHAAs (interpreted carbonates). (C) (Slow to) moderate seeps are characterized by subcircular PHAAs, and often generate sub-circular like depressions with gently dipping base. (D) Deactivation of seepage. (E) Fast seeps are represented by circular crater or characterized by absences of PHAAs. Image taken from Ho et al. (2012).

REFERENCES Ho, S., P. Imbert, and J. A. Cartwright (2012). “Fluid Venting Structures of the Lower Congo Basin on 3-D Seismic: Gas Flux Variations Recorded by the Vertical Evolution of Pockmarks and Associated Amplitudes Anomalies”, Search and Discovery Article #50763, AAPG Annual Convention and Exhibition, Long Beach, California, April 22-25, 2012.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A001

Origin and Flux of Methane Gas from Submarine Mud Volcanoes in the Upper Slope off SW Taiwan Yuchun Huang, Tsanyao Frank Yang, Nai-Chen Chen, Ching-Yi Hu Department of Geosciences, National Taiwan University [email protected], [email protected] Saulwood Lin Institute of Oceanography, National Taiwan University Song-Chuen Chen Central Geological Survey, MOEA, Taipei, Taiwan, R.O.C.

ABSTRACT Thirteen submarine active mud volcanoes, which named MV1~ MV13, have been recognized in the area between Kaoping Canyon and Fangliao Ridge, offshore southwest Taiwan. It has been considered that these mud volcanoes are closely related to the intrusion of mud diapirs. The predominant composition of those gas seeps is methane, which may escape to the atmosphere and become an important natural source of greenhouse gas. To estimate the methane flux emission via those mud volcanoes in this area, we have conducted threecruise surveys during the period of 2011-2012. In this study, we traced the location of gas plume for each mud volcano by echo sonar (EK60) survey first. And then, we can collect the water column samples right above the venting mud volcanoes, and also the sediment samples by gravity corer. The carbon isotopic data of methane gas from cored sediments range from -30 to -50 ‰. It indicates that the methane gas is mostly thermogenic in origin, and may mix with different proportions of biogenic gas source. Meanwhile, the dissolved methane concentrations of sea water above the seepages are 2-20 times higher than those in the background area. Many factors may affect the migration of dissolved methane, including the distribution of methane gas bubble sizes and upwelling / lateral current resulted by initial condition of venting. All the evidences point out the dissolved methane which supplied by deep water submarine mud volcanoes can be transferred to the shallow depth in study area. Based on the diffusive exchange equation and Fick’s First Law, the methane flux of sediment-to-bottom water and ocean-to-air can be estimated ca. 1.14 ~ 157 and 0.15 ~ 127 μmol m-2 d-1, respectively. The result shows that the sea water would play an important role in methane source to atmosphere, at least, in the studied region. Furthermore, we can have an approximate estimation of the total methane flux of ca. 4,100 kg yr-1 in this region.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A064

Temporal Variations of Methane Flux from Submarine Mud Volcanoes off Southwest Taiwan Tsung-Han Yang, Tsanyao Frank Yang, Nai-chen Chen Department of Geosciences, National Taiwan University, Taipei, Taiwan [email protected], [email protected], [email protected]

Saulwood Lin, Pei-Ling Wang Institute of Oceanography, National Taiwan University, Taipei, Taiwan [email protected], [email protected]

Shu-Kun Hsu Department of Geosciences, National Central University, Taiwan [email protected] ABSTRACT Submarine mud volcanoes are features that episodically emit gases, fluids, and mud onto the seafloor. Methane is the representative gas transport by mud volcanoes efficiently from deep buried sediment to the water column, and potentially to the atmosphere as a greenhouse gas. G96, MV10, MV1, are active mud volcanoes located on the upper slope of southwest Taiwan. G96 has plume from the top of mud volcano (360m) direct to the sea surface. Bubbles at the sea surface was observed. This study was conducted during cruise OR3 1693 in June 2013 and OR3 1755, 1756 in April 2014. To understand the activity of gas emissions of mud volcano, we scanned back and forth over mud volcanoes with 38kz echo sounder and got totally 250 acoustic images of plumes. 5 water column samples were collected above the venting of each mud volcano at the tidal maximum and minimum. Three gravity cores were taken at the mudflow site of G96. High concentration of methane (38522 ul/l) and shallow sulfate methane transition zone (~70cm) was shown in the sediment. (G96) The C1/(C2+C3) ratio from core sediment range from 29-392, indicates that the methane gas is mostly thermogenic in origin. Area of the plumes from echo sounder were calculated and show good correlation with the tide on 30th -31st May 2013 at MV10 and 14th -15st April 2013 at MV1. Flux of methane from the water column to atmosphere can be calculate by diffusive exchange equation, showing that gas emission of mud volcano G96 can largely differ (0.065, 3.426, 3.414, 0, 41.739 umol m-2 d-1) from time to time.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A021

A Newly Discovered Cretaceous Seep Carbonates in Tibet Hongpeng Tong Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, China [email protected]

Duofu Chen Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, China [email protected]

ABSTRACT A section developing Cretaceous seep carbonates was recognized in the southern Kardio village, Xigaze, Tibet. The southern Kardio seep carbonates, occurring as clustered, isolated, chimney-like and stratoid concretions, are enclosed in Cenomanian turbidite strata of the Xigaze forearc basin. These concretions consist of carbonate (63.2% on average), clastic quartz and feldspar (23.2% on average), and clay minerals (chlorite, illite and smectite, 13.5% on average). The carbonates exhibit negative δ13C values ranging from -34.1‰ to 12.9‰, indicating a carbon origin from seeping thermogenic methane. A relatively deep origin of thermogenic methane is also supported by the lower 87Sr/86Sr ratios of these samples (from 0.706221 to 0.706808). The carbonates have low δ18O values varying from -13.1‰ to -2.2‰, most of which indicate diagenetic alteration. The negative linearity between oxygen and carbon isotopic values suggests a diagenetic fluid with relatively high δ13C values and high temperature. The shale-normalized REE patterns show varied Ce anomalies. Most samples with no real Ce anomaly illustrate reducing environments. The stratoid concretions and an isolated concretion just above the clustered concretions have real negative Ce anomalies suggesting changeable redox conditions and several sudden changes of flux rate possibly resulted from suspended-reactive cycles of seep activities. Several cycles within short time are likely related with the paroxysmal activities of turbidite sedimentation, which would result in fast loading and finally promote hydrocarbon seeps. ACKNOWLEDGEMENTS This study was partially supported by the National Natural Science Foundation of China (41273041).

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A022

Microbial Turnover and Benthic Geochemical Flux of the Pockmark Field in Southwestern Xisha Uplift, Northern South China Sea: Insight from Reaction-Transport Model Min Luo and Duofu Chen Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, China [email protected], [email protected]

Andrew W. Dale and K. Wallmann Helmholtz Center for Ocean Research Kiel (GEOMAR), Germany [email protected], [email protected] ABSTRACT Pockmarks, one of the most common manifestations of fluid flow on the seafloor, are widespread along continental margins worldwide. The newly discovered mega-pockmarks in southwestern Xisha Uplift are speculated to be caused by both fluid seepage and strong bottom currents and may be presently inactive. However, quantification of microbial turnover rates and benthic flux of pore water species in this pockmark field is lacking. Thus, we calculate the early diagenetic processes controlling the particulate organic carbon (POC), methane, sulfate, calcium, and dissolved inorganic carbon turnover via a reaction-transport model. The results of transient state modeling suggest that fresher organic matter (young initial age) with higher sedimentation rate has deposited since the end of Little Ice Age (~200 yrs BP). Sulfate was consumed via organic matter mineralization at rates of 136 mmol m2- yr-1 and 108 mmol m2- yr-1 for C9 and C14, respectively, while AOM rates were 3 mmol m2- yr-1 and 12 mmol m2- yr-1. Thus, the vast majority of sulfate was consumed by OSR in C9 and about 10% of sulfate was consumed by AOM in C14. Nearly zero benthic methane flux at both cores suggests that AOM as the effective “microbial filter” consumed almost all dissolved methane ascending from underlying sediments, which could also imply that fluid seepage is currently inactive. The depth-integrated rates of DIC produced via OSR are 272 mmol m2- yr-1 and 216 mmol m2- yr-1 for C9 and C14, while the rates of authigenic carbonate precipitation amount to 39 mmol m2- yr-1 and 48 mmol m2- yr-1, respectively. The data hence suggest that 14% and 22% of DIC generated via OSR are removed by authigenic carbonate precipitation. Still, a fair amount of DIC enters the bottom water with a benthic flux of ~90 mmol m2yr-1 for both cores. Consequently, DIC derived from rapid organic matter degradation may play a significant role in carbon cycle at sediment-water interface. ACKNOWLEDGEMENTS This study was partially supported by the National Natural Science Foundation of China (91228206).

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A030

Numerical Simulation of Gas Composition Differentiation in Marine Sediments: An Application at IODP Site 1327 Yuncheng Cao and Duofu Chen CAS Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, China [email protected], [email protected]

ABSTRACT Gas hydrates are solids physically resembling ice that crystallized with inclusion of gas molecules into rigid cages of water molecules. Each water cage encloses a space of a particular size, and only a gas molecule proper enough to fit within this site can be hosted in that specific hydrate structure. Structure I methane hydrate is the most common type found in nature. Structure I gas hydrate has tow types of cages that gas molecules may be hosted. Because the larger cavities filled with ethane would be much stable than those filled by methane (Sloan and Koh, 2008), the larger cavities preferentially enclose ethane during the formation of gas hydrate, which results gas composition differentiation during gas hydrate formation. Based on the principle of gas composition differentiation, we establish a numerical model of gas composition differentiation between methane and ethane during gas hydrate accumulation and applied the model to IODP site 1327. The simulation shows that the gas composition differentiation only occurs at the interval where gas hydrate presents. The lowest methane/ethane (C1/C2) point indicates the bottom of hydrate zone, and the composition differentiation produces the upward increase of C1/C2 within the gas hydrate zone. The C1/C2 reaches the largest value at the top occurrence of gas hydrate and keeps relative stable above the top occurrence of gas hydrate. The top and bottom occurrence of gas hydrate indicated by the inflection points of the C1/C2 profile are similar to those indicated by the negative anomalies of measured chloride concentrations (Riedel et al., 2006). By comparing with the measured C1/C2, the differentiation coefficient (kh=Xe,h/Xe,w, Xe,h is C1/C2 of the formed gas hydrate, Xe,w [mol/kg] is the concentration of ethane in water ) is calculated to 70 kg/mol. The top occurrence of gas hydrate indicated by the C1/C2 profile also confines the water flux to be 0.4kg/m2-year, similar to that confined by the chloride profile. To best fit the measured C1/C2 profile, the methane flux is calculated to 0.04mol/m2-year. Therefore, the C1/C2 profile could be used to obtain the gas hydrate accumulation information. REFERENCES

Riedel M, Collett T S, Malone, M J, et al. (2006), Proceedings of the Integrated Ocean Drilling, Volume 311. Sloan D E, Koh C A. (2008), Clathrate Hydrates of Natural Gases. Third edition. CRC Press, New York,USA

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A008

Pore Water Geochemistry in Shallow Sediments in the Dongsha Area of Northern South China Sea: Evidences of the Anaerobic Oxidation of Methane and Its Impact on the Cycle of Redox-Sensitive Elements Yu Hu and Duofu Chen Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China [email protected], [email protected]

Qianyong Liang and Hongbin Wang Guangzhou Marine Geological Survey, Guangzhou 510740, China

ABSTRACT Cold hydrocarbon seepage is a frequently observed phenomenon along continental margins worldwide. However, little is known about the impact of venting reducing fluids on the cycle of redox-sensitive elements. Four gravity cores, DS08, DS05, DS07 and F sites, were collected in the Dongsha Area, northern South China Sea. The geochemistry of the pore waters, including SO42-, Mg2+, Ca2+, Sr2+, dissolved inorganic carbon (DIC), δ13CDIC values, Fe and Mn concentrations and trace elements (e.g. Mo, U), was analyzed to elucidate the biogeochemical processes associated with sulfate consumption and their influences on the cycle of redoxsensitive elements. The sulfate concentration–depth profiles, δ13CDIC value and (ΔDIC+ΔCa2++ΔMg2+) /ΔSO42ratios suggest that organoclastic sulfate reduction (OSR) is the dominant process in DS08 site, whereas, the anaerobic oxidation of methane (AOM) and OSR both control the sulfate concentration at DS05, DS07 and F sites. Based on the sulfate concentration gradient, the depth of the sulfate–methane interface (SMI) of DS05, DS07 and F sites ranged from 14 m to 7 m, and the calculated methane diffusive flux varied from 0.14 to 0.29 mol·m-2·yr-1. The relatively shallow SMI and high methane flux may be related to the occurrences of gas hydrates in this region where massive gas hydrates were sampled by drilling program in 2013. The pore-water Mg/Ca and Sr/Ca weight ratios indicate that high Mg-calcite is the dominant authigenic mineral that has recently precipitated from pore water at all the four sites. The U concentration with depth of pore water from the four sites reveals that U concentration has decreased significantly within the Fe–Mn reduction zone, and AOM has limited influence on the cycle of U. In contrast, the pore water Mo shows that gradually enhanced sulfate flux corresponds to the gradually increased removal flux of Mo in the pore water, suggesting that AOM has significantly controlled the cycle of Mo at cold seeps. Cold seep environments may serve as an important potential sink in the marine geochemical cycle of Mo.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A033

Gas Hydrate Characteristics Retrieved off Southwestern and Southwestern Sakhalin Island Akihiro Hachikubo, Hirotoshi Sakagami, Hirotsugu Minami, Satoshi Yamashita, Nobuo Takahashi and Hitoshi Shoji Environmental and Energy Resources Research Center, Kitami Institute of Technology, Japan [email protected] Young Keun Jin Korea Polar Research Institute, Korea [email protected] Olga Vereshchagina and Anatoly Obzhirov V.I. Il’ichev Pacific Oceanological Institute, FEB RAS, Russia [email protected]

ABSTRACT We report gas hydrates retrieved off southeastern and southwestern Sakhalin Island. Sakhalin Slope Gas Hydrate (SSGH) project started in 2007, and we retrieved sediment cores including gas hydrates off northeastern Sakhalin Island in 2009-2011. In the recent cruises (2012-2013), we sampled sediment cores at the Terpeniya Ridge and the Tatarsky Trough (SE and SW Sakhalin Island, respectively) in the cruises of LV59 and LV62 (R/V Akademik M. A. Lavrentyev). We found a lot of gas plumes ascend from the sea bottom and the dissolved methane in sediment pore water was rich. Dissociation heat and hydration number of gas hydrate samples were measured by a calorimeter and Raman spectrometer, respectively. Dissociation heat of gas hydrates was almost the same as that of pure methane hydrate. Raman spectra indicated that the hydrate crystals of both Terpeniya Ridge and Tatar Trough belonged to the structure I, and the hydration number was estimated about 6.0. Molecules of hydrogen sulfide were detected in the clathrate cages of the structure I. Ethane was also detected and its Raman peaks suggested the structure I. Therefore, the hydrate crystal is similar to that obtained from NE Sakhalin Island in our previous cruises. We obtained hydrate-bound gas and dissolved gas in pore water on board and measured their molecular and stable isotope compositions. Empirical classification of the methane stable isotopes; δ13C and δD indicated that the gases obtained at the Terpeniya Ridge are microbial origin via CO2 reduction, whereas some cores at the Tatarsky Trough showed thermogenic origin. We retrieved three sediment cores including gas hydrate at the Tatarsky Trough, and their δ13C of hydrate-bound methane were -47.5‰, -44.2‰, and -68.8‰, respectively. Therefore, gas hydrates encaged both microbial and thermogenic gases yield at the small region (12 km distance) of the Tatarsky Trough. Ethane-rich (up to 1% of the total guest gas) hydrates were found both at the Terpeniya Ridge and the Tatarsky Trough. Ethane δ13C of the all gas samples suggested their thermogenic origin.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A023

Low Chloride Anomalies in Sediment Pore Waters off Southwest Sakhalin Island, Russia Yota Sasaki, Hirotsugu Minami, Akihiro Hachikubo, Satoshi Yamashita, Takuma Hirano, Hirotoshi Sakagami, Nobuo Takahashi and Hitoshi Shoji Environmental Energy Resources Research Center, Kitami Institute of Technology, Kitami, Japan [email protected]

Young Keun Jin Korea Polar Research Institute, Incheon, Korea [email protected]

Nataliya Nikolaeva, Alexander Derkachev and Anatoly Obzhirov V.I. Il’ichev Pacific Oceanological Institute, FEB RAS, Vladivostok, Russia [email protected]

Boris Baranov P.P. Shirshov Institute of Oceanology, RAS, Moscow, Russia [email protected] ABSTRACT The Sakhalin Slope Gas Hydrate Project (SSGH) is an international collaborative effort by scientists from Japan, Korea, and Russia to study natural gas hydrates (GHs) that have accumulated on the continental slope off Sakhalin Island, Russia. In 2012 and 2013, the R/V Akademic M.A. Lavrentyev conducted two research cruises for the SSGH-12 and SSGH II-13 projects – the LV59 and LV62 cruises, respectively. Three GH-bearing cores LV59-27HC, LV62-17HC, and LV62-26HC and 23 GH-free cores (by visual observation) were retrieved using steel hydro- and gravity-corers in the Tatarsky Trough, off southwestern Sakhalin Island. The pore water was sampled on board the ship using squeezers designed and constructed at the Kitami Institute of Technology (KIT, Kitami, Japan). The concentrations of anions, such as chloride, sulfate, and bicarbonate, in the pore waters were measured by ion chromatograph at KIT. The sulfate concentration in the pore waters decreased linearly with core depth to the sulfate methane interface (SMI) for 22 cores. The depths of the SMIs of the GH-bearing cores LV59-27HC and LV62-17HC were 0.6 and 1.1 m below the sea floor (bsf), respectively, whereas for the GH-free cores they were 1.1‒3.6 m bsf. Since the depth of the SMI depends on the intensity of the upward methane flux, we conclude that intensive methane flux was observed at the GH-bearing core sites. The linearity of these profiles suggests that sulfate depletion is largely driven by an upward flux of methane, rather than by the flux of organic matter from above, and the anaerobic oxidation of methane (AOM) at the SMI. Three cores show concave-up sulfate profiles indicating a sudden increase in the methane flux from below, presumably caused by the formation of GH adjacent to the core sampling sites. However, the sulfate concentration in the pore water of the GH-bearing core LV62-26HC (core length: 189 cm) remains essentially constant up to the GH-bearing interval (174–189 cm bsf), with no evidence for consumption of sulfate in the pore water. Since the depth of the SMI depends on the intensity of the upward methane flux, this phenomenon suggests a very weak methane flux although GH is observed in the sediment core. Future studies are needed to understand the mechanism responsible for this phenomenon. 92

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A023 Twelve cores show that the chloride concentrations in the pore water along the whole core are similar to that of the bottom seawater. Two cores show increases in the chloride concentration with core depth, suggesting the formation of GH adjacent to the core sampling sites since ions are excluded from the water when GHs form. By contrast, the chloride concentrations in the other 12 cores, including two GH-bearing cores, are initially similar to those of the bottom seawater, and then decrease with depth. A large number of gas flares/methane plumes emerging from the seafloor were observed during these cruises at the sites where low chloride anomalies in the pore water were obtained. This finding suggests that excessive free gas could induce flow through cracks such as those produced by fracturing. If this is the case in this study area, the diffusive process as well as the chloride-depleted/free gas-rich fluid flow as an advective process may contribute to these low chloride anomalies in the pore waters. However, further studies are needed to understand these phenomena at the study area.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A037

Measurements and Prediction of Methane Hydrate Equilibrium in the Presence of Ionic Liquid 1-Ethyl-3-Methylimidazolium Chloride Che-Kang Chu, Yan-Ping Chen, Shiang-Tai Lin and Li-Jen Chen Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan [email protected]

Po-Chun Chen Central Geological Survey, New Taipei City 235, Taiwan. [email protected] ABSTRACT The dissociation conditions for methane hydrates in the presence of ionic liquid 1-ethyl-3methylimidazolium chloride were experimentally measured by using a differential scanning calorimetry operated at constant high pressure within the range from 5 to 35 MPa. In addition, a predictive method was applied to predict the vapor-liquid-hydrate three-phase equilibrium condition of methane hydrate in the presence of ionic liquid. The Peng-Robinson-Stryjek-Vera equation of state incorporated with COSMO-SAC activity coefficient model and the first order modified Huron-Vidal mixing rule were chosen to evaluate the fugacity of vapor and liquid phase. A modified van der Waals and Platteeuw model was applied to describe the hydrate phase. This predictive method can successfully describe the inhibition effect of this ionic liquid at different concentrations on the methane hydrate formation qualitatively. INTRODUCTION Gas hydrates are crystalline solids which looks like ice but gas are trapped in its water molecule cage structure which formed with hydrogen-bond. The possibly way to extract methane gas from hydrate under deep sea including in exchange carbon dioxide for methane gas and dissociating methane hydrate by hydrate inhibitor. Thermodynamic hydrate inhibitor can alter the hydrate stable region to a lower temperature and higher pressure range, it can help gas extracting from natural deep sea hydrate. Ionic liquid is one kind of salts but with a melting point below 100 oC under ambient pressure. Ionic liquid has some convenient characters like low vapor pressure, good thermal stability, and excellent solvating property, some ionic liquid also has unusual high carbon dioxide solubility. One factor to choose ionic liquid as hydrate inhibitor in this study is environment-friendly, if the ionic liquid is used to extract the hydrate in the ocean, the pollution of material must be considered. In previous research, it has found that 1-butyl-3-methylimidazolium could be broken up into small low-toxic organic compounds by electrochemical waste water treatment, and if there is an ester function group on the 1-butyl-3methylimidazolium molecule structure, the speed of biodegraded by bacterial would increasing dramatically.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A037 EXPERIMENT A differential scanning calorimeter (μ DSC 7 evo, Setaram, France) was performed at constant high pressure within the range from 5 to 35 MPa to measure the dissociation conditions for methane hydrates in the presence of ionic liquid 1-ethyl-3-methylimidazolium chloride. To control the pressure of reaction system, a motorized pump is connected to the DSC. A drop of measurement solution about 0.1 mL is loaded into reaction cell each time then the cell is pressurized to the experimenting target pressure with methane gas. For the hydrate formation and dissociation process, first the system is cooled from 298.15 K to 233.15 K at rate of 0.6 K/hour to promote hydrate formation by overcooling. Second, the system temperature is heated back to 298.15 K at a much slower rate of 0.05 K/min, hydrate dissociation temperature and enthalpy can be measured during heating. The chemical structure of ionic liquid 1-ethyl-3-methylimidazolium chloride is listed in Table 1.

Table 1: Ionic liquid, 1-ethyl-3-methylimidazolium chloride, used in this study Symbol

Chemical name

EMIM-Cl

1-Ethyl-3-methylimidazolium chloride

Chemical structure

MODELLING OF METHANE HYDRATE PHASE EQUILIBRIUM A predictive method was applied to predict the vapor-liquid-hydrate three-phase equilibrium condition of methane hydrate in the presence of the ionic liquid EMIM-Cl (Chin et al., 2013; Chin et al., 2013; Hsieh et al., 2012; Hsieh et al., 2011). At equilibrium, the fugacity of water is equal in all coexisting phases (vapor, liquid, and hydrate phase). The fugacity of vapor and liquid phase is described by the Peng-Robinson-Stryjek-Vera equation of state (Stryjek and Vera, 1986). In this work, we use the modified Huron-Vidaw (MHV1) mixing rule with COSMO-SAC activity coefficient model to acquire the parameters in PRSV EoS for mixtures. (Hsieh et al., 2012; Hsieh et al., 2011). The fugacity of hydrate phase is determined by the modified van der Waals and Platteeuw mode (van der Waals and Platteeuw, 1959), i.e, an explicit pressure dependence of the Langmuir adsorption constant in the van der Waals-Platteeuw model is applied. (Hsieh et al., 2012) RESULTS AND DISCUSION The experimental data of pure methane hydrate and methane hydrate in the presence of 10 wt%, 20 wt% and 40 wt% EMIM-Cl are shown in Fig. 1. It was found that the inhibition effect of EMIM-Cl of 10 wt% is less than 2 K. But as the EMIM-Cl concentration is increased up to 40 wt%, the inhibition effect of EMIM-Cl would lower the dissociation temperature by 12 K. The predictive method used in this study slightly overestimates the inhibition effect of EMIM-Cl on methane hydrate formation, but successfully describes the tendency of phase behavior of methane hydrate in the presence of EMIM-Cl in the range of 10 to 40 wt%. 95

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A037

Fig. 1: Pure methane hydrate (filled black square) (Sloan and Koh, 2007) and methane hydrate in the presence of EMIM-Cl of different concentrations: black square, pure water; blue triangle & blue curve, 10 wt%; red dimond and red curve, 20 wt%; green circle and green curve, 40 wt%. CONCLUSIONS EMIM-Cl acts as an inhibitor on the methane hydrate formation. As the concentration of EMIM-Cl is increased, the ability of inhibition of EMIM-Cl is much enhanced. The predictive method successfully describes the tendency of phase behavior of methane hydrate in the presence of EMIM-Cl without any fitting parameter. REFERENCES Chin, H.-Y., M.-K. Hsieh, Y.-P. Chen, P.-C. Chen, S.-T. Lin and L.-J. Chen, (2013). "Prediction of Phase Equilibrium for Gas Hydrate in the Presence of Organic Inhibitors and Electrolytes by Using an Explicit Pressure-Dependent Langmuir Adsorption Constant in the van der Waals–Platteeuw Model." The Journal of Chemical Thermodynamics, 66, 34-43. Chin, H. Y., B. S. Lee, Y. P. Chen, P. C. Chen, S. T. Lin and L. J. Chen, (2013). "Prediction of Phase Equilibrium of Methane Hydrates in the Presence of Ionic Liquids." Industrial & Engineering Chemistry Research, 52, 16985-16992. Hsieh, M.-K., W.-Y. Ting, Y.-P. Chen, P.-C. Chen, S.-T. Lin and L.-J. Chen, (2012). "Explicit Pressure Dependence of the Langmuir Adsorption Constant in the van der Waals–Platteeuw Model for the Equilibrium Conditions of Clathrate Hydrates." Fluid Phase Equilibria, 325, 80-89. Hsieh, M.-K., Y.-T. Yeh, Y.-P. Chen, P.-C. Chen, S.-T. Lin and L.-J. Chen, (2011). "Predictive Method for the Change in Equilibrium Conditions of Gas Hydrates with Addition of Inhibitors and Electrolytes." Industrial & Engineering Chemistry Research, 51, 2456-2469. Sloan, E. D. and C. Koh (2007). Clathrate Hydrates of Natural Gases, Third Edition, CRC Press. Stryjek, R. and J. H. Vera, (1986). "PRSV: An Improved Peng—Robinson Equation of state for Pure Compounds and Mixtures." The Canadian Journal of Chemical Engineering, 64, 323-333. van der Waals, J. and J. Platteeuw, (1959). "Clathrate Solutions." Adv. Chem. Phys, 2, 1-57. 96

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A053

Geothermal Gradient and Heat Flows in the Continental Slope of the Northern South China Sea near Taiwan Wei-Zhi Liao, Andrew T. Lin Department of Earth Sciences, National Central University [email protected], [email protected]

Char-Shine Liu Institute of Oceanography, National Taiwan University [email protected]

Jung-Nan Oung CPC Corporation, Taiwan

Yunshuen Wang Central Geological Survey, MOEA, [email protected] ABSTRACT We use Bottom Simulating Reflectors (BSRs) from reflection seismic images and hydrocarbon exploration boreholes to derive geothermal gradients and heat flows in the northern margin of the South China Sea near Taiwan. Sub-bottom temperatures are calculated from BSRs and from measured bottom-hole temperatures using Horner-plot method for temperature corrections at exploration wells. Our results show that the geothermal gradients and heat flows in the study area range from 28 to 128 ℃/km and 40 to 159 mW/m2, respectively. It is cooler beneath the shelf with an averaged geothermal gradient of 34.5 ℃/km, and of 62.7 mW/m2 for heat flows. The continental slope shows a higher averaged geothermal gradient of 56.4 ℃/km, and of 70.9 mW/m2 for heat flow. This feature is most likely caused by thicker sediments that have accumulated beneath the shelf comparing to thinner sediment thickness beneath the slope. In addition, the continental crust is highly extended beneath the continental slope. A north-dipping graben-bounding fault exists beneath the upper slope and yields higher heat flows in the Jiulong Ridge, indicating vigorous vertical fluid convection taking place along this fault. Our study also reveals that the crust in the Tainan Basin is a little cooler than others in the northern margin of the South China Sea in the west. It is hotter, however, than the adjacent Taiwan accretionary wedge in the east.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A054

Climatic Change and Records of AOM in the Lake Baikal Freshwater Environment Wan-Yen Cheng, Jing-Yang Tseng, Saulwood Lin, and Chieh-Wei Hsu, Institute of Oceanography, National Taiwan University, Taipei, Taiwan [email protected], [email protected], [email protected], [email protected]

Genady V. Kalmychkov Institute of Geochemistry, Siberian Branch, Russian Academy of Sciences [email protected]

Tatyana V. Pogodaeva Limnological Institute, Siberian Branch, Russian Academy of Sciences [email protected]

ABSTRACT In marine environment, anoxic oxidation of methane (AOM) is an important mechanism in removing methane before seeping to the upper water column. In freshwater environment, e.g., Lake Baikal, sulfate is usually low in concentration and hence could not act as an important mechanism in removing methane and its subsequent emitting into the atmosphere. Watanabe et al. (2004) indicated that rivers could carried extra sulfate into the Lake during warm period and supplying AOM reaction in leaving higher concentration of pyrite in sediment record. However, venting from gas hydrate dissociation and hydrothermal fluid have been found in the Lake which may provide additional sulfur to the lake water. In order to better understand role of sulfate and AOM reaction in the freshwater Lake Baikal, a set of 15 gravity cores were collected together with 15 river water from surrounding rivers, and 18 sites of hot spring waters. Analytical works include water sulfate, chloride, methane, alkalinity, stable isotopic oxygen of water and sediment organic carbon, organic nitrogen, carbonate content, pyrite, biogenic silica, grain sizes, stable isotopic methane carbon, stable isotopic sulfur and sediment iron content. Age of the sediments was determined by C14 analysis of sediment organic carbon and biogenic silica variations. Contrary to Watanabe’s result, our results show that pyrite accumulation did not occur during climatic warm period but during climatic cold period. During warm period, river water do carry sulfate to the Lake, however, well-circulation of Lake water also carried sufficient oxygen to the Lake bottom. As a result, limited accumulation of pyrite occurred in sediments by preventing AOM reaction in the oxygenated environment. Our result indicated that during climatic cold period, retarded or slow Lake water circulation favor the AOM reaction in inducing a high concentration of pyrite accumulation.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A055

Using Ethanol Vapor as Catalyst for Decomposing Artificial Methane Hydrate Po-Chun Chen, Kuan-Chen Liu, San-Hsiung Chung, and Yunshuen Wang Central Geological Survey, MOEA., Taiwan [email protected], [email protected], [email protected], [email protected]

ABSTRACT At atmospheric pressures methane hydrates display unexpected slow dissociation rates in a temperature window slightly below the melting point of ice. This phenomenon which is called “self-preservation” allows methane hydrate to exist at unequilibrium pressures and temperatures for a relatively long period of time. In this study, we demonstrated that the “self-preservation phenomenon” can be destroyed entirely by introducing just few ethanol into the system (stand still time can be as short as 4 hours) without adjusting any other parameters. This discovery may play an important and practical role in the regasification stage while utilizing artificial gas hydrates as a medium for transporting natural gas. KEYWORDS Gas hydrate; methane hydrate; ethanol; catalyst; ice powder; synthesize; vapor. INTRODUCTION Yakushev and Istomin (1992) reported that at atmospheric pressures methane hydrates display dissociation rates several orders of magnitude lower than expected from extrapolation of the dissociation kinetics in a temperature window slightly below the melting point of ice. It is called “Self-preservation phenomenon” or “Anomalous preservation” which allows gas storage with low boil off rates at very moderate P/T conditions (Rehder et al., 2012). The interest in self-preservation is caused by the possible application of this effect for storage and transportation of natural gas (Subbotin et al., 2007) even if this same characteristic turns in a drawback during the regasification stage. However, if the decomposition rate of gas hydrates can be accelerated by adding some trace additives instead of rising ambient temperature, we suppose that the energy efficiency of gas hydrate transportation technology can be improved further. APPARATUS The apparatus (Fig. 1) used for synthesis of methane gas hydrate (MGH) was modified from Stern et al. (1996, 2000). The system was equipped with a freezer (∼240 K) within which a trapezoidal copper vessel (25.5×50.5 cm width × 51.5 cm length × 23 cm height) was set on a heating plate (25.5 × 51.5 cm). The copper vessel held a fluid bath of 95% ethyl alcohol aqueous solution, in which two pressure vessels (reservoir and reactor, both made of stainless steel with a total inner volume of 315 cm3) were immersed. The sample holder was a high-density polyethylene (HDPE) cylinder (5 cm outer diameter and 4.8 cm inner diameter, with a length of 8 cm and wall thickness of 0.1 cm).

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A055 The methane pressure was increased using a gas booster and monitored using a pressure transducer. The pressures reported were absolute pressure with an accuracy of (0.02%. Four type-K thermocouples were used to independently monitor the bath temperature, gas temperatures within both the reservoir and reactor, and midspecimen sample temperature. The reliability of pressure and temperature data was verified by determining the P-T equilibrium boundary between methane hydrate and methane + water. One syringe pump was used for injecting liquid additives into the system in the high-pressure environment.

Fig. 1: Experimental apparatus. The dashed line frame indicates the refrigerator (not to scale). EXPERIMENTAL PROCEDURES Methane hydrate samples were synthesized from ultrapure methane (99.99%) and seed ice (50.7g, grain sizes ranging from 180 to 250 μm, prepared from a nearly gas free ice block made from ultra-pure deionized water) through exactly the same P-T-t path. Once hydrate synthesis process was finished, we would assign every experiment a different decomposition temperature and started the dissociation stage. In another two experimental series, volatile ethanol was chosen as the additive and injected into the system by a syringe pump right before and after the synthesis stage. At the dissociation stage, we rapidly vented the reactor pressure to 0.1 MPa over 10 s to destabilize the MGH and started the dissociation. The system vent was then immediately closed, while simultaneously opening the valve connecting the sample to the flow meter, allowing for collection and measurement of all released methane. The cumulative weight of displaced water in the flow meter and gas collection apparatus was continuously monitored for getting the information of dissociation rate. From the displaced water weight, we could get the released methane volume from the displaced water weight and then calculated the methane hydrates yield.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A055 RESULTS AND DISCUSSION From the experiments without additive (Solid red dots in Fig. 2 and paths in Fig. 3), we could recognize that methane hydrates indeed exhibit an anomalous “Self-preservation phenomenon” in a temperature window around 265.2 to 272.2K. Even standing still for 24 hours, more than half of methane molecules were still trapped in hydrates while the decomposition temperature was set at 272.2K. Stern (2011) reported that methane hydrates possess the lowest decomposition rate around 268.2K at which we got the second low decomposition rate. Among the second experimental series in which ethanol was added before the synthesis stage, the “Selfpreservation phenomenon” could be destroyed intensely (blue solid squares in Fig. 2). This interesting finding caught our attention and inspired us to conduct the third experimental series in which ethanol was introduced into the system after the synthesis stage (green open dots in Fig. 2). Again, the “Self-preservation phenomenon” was wiped out and hydrates decomposed even quicker in this series.

Fig. 2: Cumulative amount of released methane (24 hours after the start of decomposition).

Fig. 3: Cumulative amount of released methane during decomposition stage (experiments without additive). The system was heated purposely over 283K after 24 hours for decomposing all residual hydrates. 101

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A055 CONCLUSIONS In this study, we demonstrated that the self-preservation phenomenon of methane hydrates can be nearly destroyed with the existence of trace ethanol vapor. Such findings may be of importance in the regasification stage while utilizing artificial gas hydrates as a medium for transporting natural gas. Nevertheless, the mechanism behind this phenomenon is still unclear and needs further exploration. REFERENCES Rehder, G., R. Eckl, M. Elfgen, A. Falenty, R. Hamann, N. Kahler, W.F. Kuhs, H. Osterkamp and C. Windmeier (2012), “Methane Hydrate Pellet Transport Using the Self-Preservation Effect: A Techno-Economic Analysis,” Energies, 5, 2499–2523;doi:10.3390/en5072499. Stern, L.A., S.H. Kirby and W.B. Durham (1996), “Peculiarities of Methane Clathrate Hydrate Formation and Solid-State Deformation, Including Possible Super Heating of Water Ice,” Science, 273, 1843-1848. Stern, L.A. (2000), “Laboratory Synthesis of Pure Methane Hydrate Suitable for Measurement of Physical Properties and Decomposition Behavior,” Natural Gas Hydrate in Oceanic and Permafrost Environments, Max, M.D. (ed), Kluwer Academic Publishers, Netherlands, 323-348. Stern, L.A., S. Circone, S.H. Kirby and W.B. Durham(2001), “Anomalous Preservation of Pure Methane Hydrate at 1 atm” J. Phys. B. Chem, 105, 1756-1762. Subbotin, O.S., V.R. Belosludov, T. Ikeshoji, E.N. Brodskaya, E.M. Piotrovskaya, V. Sizov, R.V. Beloslufov and Y. Kawazoe (2007), “Modeling the Self-Preservation Effect in Gas Hydrate/Ice systems,” Materials Transactions, 48(8), 2114–2118. Yakushev, V.S. and V.A. Istomin (1992), “Gas-Hydrates Self Preservation Effect,” In Physics and Chemistry of Ice; Hokkaido University Press: Sapporo, Japan, 136-139.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A056

Observation and Quantification of Bubble Gas Escapes in Lake Baikal with Echosounder Makarov Mikhail Mikhailovich, Kucher Konstantin Miroslavovich, Granin Nikolay Grigorievich, Gnatovskiy Ruslan Yurievich. Limnological institute of the Siberian Branch of the Russian Academy of Sciences, Ulan Bator St. - 3, Irkutsk, Russia. [email protected], [email protected], [email protected], [email protected]

Muyakshin Sergey Ivanovich. Nizhny Novgorod State University. NI Lobachevsky.Gagarin Avenue - 23, Nizhny Novgorod, Russia. [email protected] ABSTRACT The results of methane flux evaluation of bubble gas escapes from the bottom of Lake Baikal are presented. Three groups of these escapes (deep, mid and shallow) were identified. The correlation between “flare” height and gas flux was determined for each group. Several deep flares demonstrated eruptive activity. INTRODUCTION Lake Baikal is located in the central part of the Asian continent between 51° 27.5' and 55° 46.3'N and 103° 42.5' and 109° 57.5'E at 456 m above sea level (Fig. 1). The length of the lake is 636 km and the width reaches 79 km. The water area of the lake is 31,722 km2 with water volume of 23,615 km3. This is about 20% of the world’s surface fresh water reserves (Shimaraev et al., 1994).

Fig. 1. Map of gas escapes at Lake Baikal

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Lake Baikal was inscribed by UNESCO on the World Heritage List. Some of the unique specific features of the lake include gas hydrates found in the near-bottom sediment layers, as well as numerous gas escapes of methane bubbles, the so-called “flares”, from the lake bottom (Granin et al., 2002). A regular search and monitoring of bubble gas escapes started in the 2000s with echosounders. More than 100 shallow bubble gas escapes (whose depth did not exceed the depths gas hydrate stability, it is 380 m for Lake Baikal), and over 20 deep bubble gas escapes were recorded in the lake (Granin et al., 2010). More than 90% of shallow gas escapes were located in the Selenga River delta. Deep gas escapes were found in all basins of Lake Baikal: southern, central and northern (Fig. 1). Maximal height of the flare (1025 m) was registered at 1300 m at the Malenky mud volcano. The deepest gas escape "St. Petersburg" was recorded at 1390 m in the central basin near the St. Petersburg mud volcano. According to our data, its height was 950 m. The total area of lake bottom deeper than 380 meters that was covered by regular echosounding surveys (2005-2012) was 42, 28 and 19% for southern, central and northern basins, respectively. To date, about 28% of the entire Lake Baikal area has been investigated. Echosounding gives a possibility to detect bubble gas escapes and assess bubble gas fluxes. As a result of our investigations, we revealed regularities of flares distribution with depths and identified correlation between flare height and its gas flux. CORRELATION BETWEEN GAS FLUX AND FLARE HEIGHT To perform acoustic measurements in Lake Baikal, the calibrated single-beam echosounder Furuno FCV1100 was used at 28 kHz frequency with 24° beam width. Software and hardware systems were specially developed to obtain and store digital data from the echosounder concurrently with data from GPS. Bubble methane flux was estimated as described by Muyakshin and Sauter (2010). This technique was based on the principle of noncoherent combining of echo intensity, taking in account bubbles size distribution and speed of their ascending and interpretation of impulse echosounder volume as a spatial filter. Granin et al. (2012) presented the first results on the application of this technique for studying of four deep flares (>380 m) in Southern and Central Baikal.

Fig. 2. Correlation between flare height and gas flux

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A056 According to the data of 2010-2013, 20 flares were detected at mid (380÷700 m) and shallow (<380 m) depths. A threshold value of volume scattering cross-section (-80 dB/m-1) was introduced for assessment of flare height. Flare heights varied from 100÷300 m (at fluxes 1÷30 t/year) to 500÷900 m (at fluxes 30÷110 t/year). Flares at 900÷1300 m never ascend higher than the depth of gas hydrate stability even at fluxes of 30÷100 t/year. At the same time, flares at 400÷600 m almost reach the surface at comparable fluxes (Fig. 2.). The height of flares emerged at 400÷600 m dropped rapidly with flux decrease (< 30 t/year). OBSERVATION OF GAS ERUPTION Several cases of “eruptions” – the beginning of bubble gas escapes activity have been registered. One of the events was registered at the Malenky mud volcano at 1:22 a.m. on 18 July, 2012 (Fig. 3a). The flare height increased up to 783 m for less than an hour, and average velocity of the flare height rise was 17 cm/s. This velocity is typical for bubbles with a diameter of 1-2 mm (McGinnis et al., 2006). The successive batches of bubbles escaped every 2-7 min. Another eruption was registered at a depth of 1390 m at 3:28 a.m. on 19 July, 2012 at the St. Petersburg bubble gas escape (Fig. 3b). The scientific research vessel stayed above the gas flare for a long time because there was no drift on the lake. It allowed us to continuously observe the cloud of gas bubbles ascending after the eruption. The flare height increased up to 905 m for 1 hour and 19 minutes. Average velocity of bubbles ascending was 19 cm/s. The successive batches of bubbles discharged every 7-11 min. One more eruption was registered at the Malenky mud volcano a two month later at 3:04 a.m. on 6 September, 2012. Average velocity of the flare height rise was 18 cm/s, the height being 450 m. Average velocity of the flare height rise was 18 cm/s, ultimately flare height increased up to 450 m. The successive batches of gas erupted every 3-8 min. The first two eruptions were registered for a comparatively short period of time. The gas escape was likely provoked by earthquakes that had happened shortly before that time.

Fig. 3. a – Eruption of the “Malenky” flare on 18.07.2012, b – Eruption of the “St. Petersburg” flare on 19.07.2012 CONCLUSION Three groups of bubble gas sources were identified: deep (h>1000 m), mid (1000 m > h > 380 m) and shallow (h < 380 m) at depths above the gas hydrate stability zone. Each group had its own logarithmic correlation between the height of acoustic gas “flare” and its gas flux. The results of this investigation can be used for quick (rough) quantification of gas flux from known flare height and for determination of the effect of gas fluxes on water mixing in Lake Baikal. The eruptive activity of some deep sources was observed. 105

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A056 REFERENCES M.N. Shimaraev, V.I. Verbolov, N.G. Granin, P.P. Shertyankin (1994), “Physical limnology of Lake Baikal”, BICER, Irkutsk-Okayama N.G. Granin, L.Z. Granina (2002), “Gas hydrates and gas venting in Lake Baikal”, Russian Geol Geophys, (43),629–637 N.G. Granin, M.M. Makarov, K.M. Kucher, R.Y. Gnatovsky (2010), “Gas seeps in Lake Baikal – detection, distribution, and implications for water column mixing”, Geo Marine Letter, (30), 399–409. N.G. Granin, M.M. Makarov, S.I. Muyakshin, K.M. Kucher, L.Z. Granina (2012), “Estimation of methane fluxes from bottom sediments of Lake Baikal”, Geo Marine Letter, 32(5-6), 427-436. McGinnis, D. F., J. Greinert, Y. Artemov, S. E. Beaubien, and A. Wu¨est (2006), “Fate of rising methane bubbles in stratified waters: How much methane reaches the atmosphere?”, J. Geophys. Res., 111, C09007, doi:10.1029/2005JC003183. S.I. Muyakshin, E. Sauter (2010), “The hydroacoustic method for the quantification of the gas flux from a submersed bubble plume”. Oceanology, 50(6), 995–1001.

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P-Wave Velocity Model above the Formosa Ridge (Southwest Off Taiwan) From Combined Analysis of OBS and Multichannel Seismic Reflection Data Elodie Lebas, Theresa Roth, Christian Berndt, Marion Jegen, Anne Krabbenhoeft, Cord Papenberg and Anke Dannowski Marine Geodynamics, GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]

Wu-Cheng Chi Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan [email protected] ABSTRACT Twelve ocean bottom seismometer (OBS) stations were deployed during the TAIFLUX oceanographic cruise (R/V Sonne, 2013) along a NW-SE transect above the Formosa Ridge, southwest off Taiwan. Six 2D seismic reflection lines oriented E-W (4), NW-SE and NE-SW were collected above the ridge as well as a 3Dcube of 10.5 km length to 2.5 km width, in a NW-SE direction, using the P-Cable system (Fig.1). A 105/105 cu-in GI gun source was used for collecting the two datasets. Analysis of the multichannel seismic reflection (MCS) lines allows recognition of a prominent bottom-simulating reflector (BSR) below the ridge whose depth varies considerably from 150 ms TWT to the north (in the canyon area) to 500 ms TWT below the summit area. Reverse polarity associated with the BSR indicates that it results from the presence of free gas below gas hydrate accumulations. The MCS data reveal important sedimentological changes throughout the Formosa Ridge with a predominance of older refilled canyons in the northern part of the ridge; while the southern part is mainly composed of contourite deposits. Ubiquity of the BSR within the ridge indicates that these sedimentological changes have little effect on free gas distribution. Several prominent seismic horizons could be picked throughout large parts of the 3D MCS cube and can be matched to arrivals in the OBS data. These horizons in addition to the BSR were used to construct a seismic velocity model by forward modeling using the Rayinvr software. Here, we present a first P-wave velocity model above Formosa Ridge based on combined analysis of OBS and 3D MCS data. Anomalous high seismic velocities indicate hydrate accumulations at various depth within the hydrate stability zone.

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Fig.1: Location of the twelve OBS the Formosa Ridge during the TAIFLUX oceanographic cruise (R/V Sonne, 2013). Blue lines represent the OBS shooting profiles and the rectangle, the area where the P-Cable data have been collected. Black dashed line corresponds to the MCS profile shown in Figure 2.

Fig.2: Multischannel seismic reflection profile collected along the Formosa Ridge showing the overall subbottom depth variation of the BSR identified within the ridge. Important sedimentological changes are highlighted from the MCS data with a predominance of older refilled canyons in the northern part of the ridge (erosional unconformities) to a prevalence of contourite deposits in the southern part. Pipe structures and seep sites are also observed. Location of the seismic line is shown in Figure 1. 108

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A074

Response of the Cascadia Margin Gas Hydrate Reservoir to Warming North Pacific Intermediate Water Evan A. Solomon, Susan Hautala, H. Paul Johnson, Una K. Miller, Brendan Philip School of Oceanography, University of Washington, USA [email protected], [email protected], [email protected]

Robert Harris College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, USA [email protected]

ABSTRACT Gas hydrates are stable at moderate pressures and low temperatures, and are ubiquitous in sediments at continental margins worldwide. Considering their widespread occurrence, they represent one of the largest reservoirs of organic carbon on Earth. As a result of the positive geothermal gradient in the seafloor, gas hydrates exist as a stable phase only within the upper few hundred meters of continental slope sediments. The upper limit of gas hydrate stability depends on bottom water temperature and is generally around 500 m outside the Arctic for Structure I gas hydrate. This up-slope limit of hydrate stability represents one of the most climate-sensitive boundaries for the global gas hydrate reservoir. Compared to other climate-sensitive gas hydrate accumulations, including those associated with thinning Arctic permafrost, continental slope hydrates are located in close proximity to actively circulating seawater. This close physical association promotes hydrate dissociation over relatively short timescales in response to modest seawater warming at intermediate depth; periods of tens of years vs. 102 to 103 years for other climate sensitive deposits (e.g. Berndt et al., 2014; Ruppel, 2011). Thus, documenting the vulnerability of these deposits to ocean warming is important for understanding the response of methane hydrate systems to environmental change. The additional flux of hydrate-derived methane to the ocean could contribute to local ocean acidification and hypoxia through microbial oxidation of methane, play a role in upper continental slope stability, and potentially increase the emission of CH4 and methane-derived CO2 from the ocean to the atmosphere. The Cascadia margin in the NE Pacific contains a large inventory of methane hydrate (e.g. Riedel et al, 2006; Tréhu et al., 2004). In order to examine whether gas hydrates on the upper continental slope are susceptible to contemporary bottom water warming, we collected all available high-resolution CTD, glider, and ARGO float temperature profiles that extend to a depth of at least 200 m along the Washington state sector of the Cascadia margin. The data was rigorously filtered and processed, and, when averaged over the entire region, the temperature at the upper limit of gas hydrate stability shows significant warming over the last 40 years.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster session II: September 2nd (15:50-16:30)-GIMS12A074 We used a 2-D finite element heat flow model to simulate the change in temperature distribution in the shallow sediments at the upper limit of gas hydrate stability resulting from the observed bottom water warming. The model includes the thermodynamics of Structure I methane hydrate and simulates the shoaling of the gas hydrate stability zone and downslope propagation over the period of historical warming. Our simulations show a significant retreat in the gas hydrate stability zone of ~1 km downslope. Recent field programs along the Washington and Oregon margins have revealed evidence for water column bubble plumes emanating from seafloor seeps within the region of gas hydrate dissociation simulated in our models. These observations suggest a significant fraction of the methane present in the sediments impacted by contemporary warming is emitted to the water column as has been observed offshore Svalbard (Westbrook et al., 2009; Thatcher et al., 2011; Berndt et al., 2014). Many recent studies investigating gas hydrate dynamics associated with contemporary warming have focused on Arctic environments. Our observation-based results highlight the importance of contemporary intermediate-depth water warming to a mid-latitude gas hydrate reservoir, and suggest downslope retreat of the upper limit of the Cascadia margin gas hydrate reservoir will likely continue into the future. To fully understand the impact of bottom water warming on the Cascadia margin gas hydrate system and the effect of enhanced methane emissions on regional biogeochemical cycles will require direct seafloor and water column sampling and eventual long-term monitoring.

REFERENCES Berndt, C., Feseker, T., Treude, T., et al. (2014), “Temporal constraints on hydrate-controlled methane seepage off Svalbard”, Science, 343, 284-287. Riedel, M., Collett, T. S., Malone, M. J., Expedition 311 Scientists (2006), Proceedings of the Integrated Ocean Drilling Program Expedition 311, IODP, Washington DC. Ruppel, C. D. (2011), “Methane Hydrates and Contemporary Climate Change”, Nature Education Knowledge, 3 (10):29. Thatcher, K. E., Westbrook, G. K., Sarkar, S., Minshull, T. A. (2013), “Methane release from warming-induced hydrate dissociation in the West Svalbard continental margin: Timing, rates, and geological controls”, J. Geophys. Research: Solid Earth, 118, 22-38. Tréhu, A.M., Torres, M.E., Bohrmann, G., and Colwell, F.S. (2006). “Leg 204 synthesis: gas hydrate distribution and dynamics in the central Cascadia accretionary complex”. In Tréhu, A.M., Bohrmann, G., Torres, M.E., and Colwell, F.S. (Eds.), Proc. ODP, Sci. Results, 204: College Station, TX (Ocean Drilling Program), 1–41. doi:10.2973/odp.proc.sr.204.101.2006. Westbrook, G. K., Thatcher, K. E., Rohling, E. J., et al. (2009), “Escape of methane gas from the seabed along the West Spitsbergen continental margin”, Geophys. Res. Lett., 36, doi:10.1029/2009GL03191.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VII: September 3rd (08:30-09:10) Keynote speech

10 Years Shallow Gas Hydrate Exploration in Japan Sea Ryo Matsumoto Meiji University - Gas Hydrate Laboratory [email protected]

ABSTRACT Japan has two contrasting types of marine gas hydrates. One is deep-seated, stratigraphic accumulation of fine grained hydrates in Nankai Trough, western Pacific (Type 1) and the other is nodular to platy accumulation in shallow mud and clay in the eastern margin of Japan Sea (Type 2). Japan's national project of gas hydrates exploration has been largely focused on Type 1 in Nankai trough since 1995, leading to offshore production test in 2013, whereas, Type 2 in Japan Sea has been investigated from viewpoints of scientific interests since 2004. 10 years exploration in Japan Sea have revealed that shallow gas hydrates 1) occur in gas chimneys ("acoustic chimney") in close association with active methane seeps, wide spread bacterial mat and carbonate concretions and pavements, 2) grow in mud and silt in gas chimney structure, displacing sediment particles, 3) often coexist with free gas as indicated by anomalously low Vp, 1.0 to 1.3 km/sec, and 4) are composed of mixed thermogenic-microbial gases with wide range of carbon isotopic composition. Shallow gas hydrates had not been seriously considered as natural gas resources because the distribution were believed to be limited within a smaller gas chimneys in Joetsu basin, however, recent regional mapping has identified similar gas hydrate bearing structures in Mogami trough to the north and Oki trough to the west. Responding to the outcome of recent academic research and expeditions, METI (Ministry of Economy, Trade and Industry) launched national program to explore shallow gas hydrates of Japan Sea in 2012. Thus, the exploration of Japan Sea gas hydrates has been drastically changed. In this paper, I will present the recent development and outcome of shallow gas hydrate exploration in Japan Sea.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VII: September 3rd (09:10-09:30)

Field Experiments on Decomposition of Deepwater Gas Hydrates during the Lifting from the Bottom to the Surface. Alexander V. Egorov and Robert I. Nigmatulin PP Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia [email protected]

Alexey N. Rozhkov A. Ishlinsky Institute for Problems in Mechanics, Russian Academy of Sciences, Moscow, Russia [email protected] ABSTRACT Gas hydrates (GH) are of practical interest mainly as a huge potential resource of hydrocarbons. Despite the fact that many of hydrate accumulations found in the ocean, cost-effective technology for their exploitation has not yet developed. Among the various types accumulations can be identified GH GH are exposed on the seabed. Now are known at least 5 regions with such manifestations of GH. The exploitation of GH outcrops on the sea floor probably the most simple. Their discovery and research is caused by use of different types of submersibles, as manned and autonomous. In the future the geography of such accumulations will be increasingly expanding. Using submersibles opens wide possibilities for full-scale studies of the properties of GH. Such studies allow us to solve many problems associated with the GH technologies. It is important that the full-scale experiments provide able to observe the progress of these processes. This report is dedicated to the description of set of experiments on the decomposition of solid natural GH during the crossing of the phase boundary of their stability. During the Russian Academy of Sciences “MIRI na Baikale, 2008-2010” expedition, deep-water researches in Lake Baikal by means of manned submersible (MS) MIR were carried out. Outcrops of massive gas hydrate (GH) directly in water were discovered in the small cleft on one of hills located in a zone of active faults at the depth of 1400 meters. In addition to outcrops GH of over an area of km2 under a thin layer of sediment were found vast fields of monolithic GH. The experiments were carried out with fragments broken off from GH monolith (Fig. 1).

Fig. 1 Outcrops of the massive GH in a small cleft on the top of GH hill (1400 м), The semi-transparent piece of monolithic hydrate similar to ice, in the manipulator’s arms. 112

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VII: September 3rd (09:10-09:30) While MS MIR has not floated above the phase stability GH grasped by the manipulator remained unchanged. Further were recorded the following the stage of decomposition GG:  Cracks occur; inside the methane bubbles are formed.  Establishing network of cracks, of which there is intense release of same size bubbles.  Small bubbles Stok’s size formed on the outer surface of GH in the form of falling down turbidity.  Breakup of monolithic piece of GH into fragments takes place.

Fig. 2 The stages of decomposition of GH which is kept in the mechanical arms during lifting upper phase boundaries The experiment for lifting GH on shipboard in an open container were carried out. We used the selfconservation effect of the GH. The GH sample clamped in the gripper of the mechanical arm washed with the ambient water whose temperature was close to 3.2–3.5°С. Only the thin layer of surface water warms up to 10– 12°С by late summer. Evidently, to reduce the uptake of heat, it was necessary to prevent the direct contact of the GH with the ambient water. For this purpose, it was proposed to put the GH into a container with an open bottom. Being similar to ice in its physical features, the GH came to the upper part of the container and remained there. To improve the thermal insulation, it would be desirable to put the GH into a gaseous medium which heat conduction in several orders less than the heat conduction of water. The GH itself has helped to solve the problem because it decomposed out of hydrate stability zone. The liberated gas ejected water from the container while the GH floats at the surface being 9/10 submerged according to its volume. As the water becomes completely displaced from the container, the largest part of the GH may go outside to be heated by the surrounding flow. Thus, the block of GH can be entrained by the flow and lost. To avoid the situation, we placed 113

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VII: September 3rd (09:10-09:30) a grid which keeps GH inside the container, In order to balance the buoyancy of the container after filling it with gas we increased the weight of the bucket with the ballast which weight slightly exceeded the buoyancy. We used a 12 l bucket with the kentledge of 13 kg (Fig. 3). The kentledge was a plastic hose filled with nickel shot. A handle suitable for the gripper of the arm of the MIR was riveted to the bucket’s bottom. A thin perforated aluminum disk fixed on stems within 5 cm of the bottom of the container for the samples served as a grid. The container with GH was placed over the grid so that the latter occurred inside the bucket. Before lifting to 106 m there was nothing then has begun the first gas outbursts from the “bucket” occurred, and the subsequent surfacing was accompanied by intensive gas bubble liberation and large groups of bubbles went off through the open bottom of the container. At the surface the bubbles continued to escape from the “bucket.” On shipboard the “bucket” container was dismantled and a multitude of almond nut size white pieces of the GH were seen on the grid dominated by a large block more than 10 cm across. Being placed in water, the small pieces rapidly decomposed, the whole mass of the GH crackled, and tiny splinters flew off the mass. The GH pieces were selected for analyses.

G

Fig. 3 The sketch of the “bucket” container. GH decomposes and gas displaces water from the container completely. The additional gas leaves the bucket through the open bottom. Filling the “bucket” container with the GH.

To carry out temperature measurement container has been modified. Temperature sensors were installed under the cap of the container and on the grid for GH. Container loaded with GH was installed in receiving bunker such a way that the grid is provided inside the container. When lifting the container both sensors recorded a monotonous change of temperature with depth (Fig. 3). Initially this change was insignificant. The upper sensor showed a stronger decrease in temperature than the bottom. This is due to the expansion of a small amount of gas that is in contact with an upper temperature sensor during lifting. Lower sensor during lifting seems, was in an aqueous medium and its indications, however, slightly different from ambient temperature.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VII: September 3rd (09:10-09:30) Temperature curves have a break at a depth of 300-250 meters. This is due to the energy consumption during the decomposition of GH. For the upper sensor temperature falls faster because of the lower heat capacity of the gas phase and from carry out the work expanding gas against the external pressure during the ascent. When crossing the mark of depth of 200 meters in the gas phase temperature becomes negative -0.25 0C, and remains so until the ascent to the surface (Fig. 4). Cooling the bottom of the container with the fragments of GH to the freezing temperatures, takes place on 100 meter mark. At this depth, the water is completely displaced from the container with methane formed by the decomposition of GH. Cooling to a negative temperature (Celsius) leads to the freezing of the water released during the GH decomposition. Hydrate surface is covered by ice shell, which prevents degradation. There is a well-known effect of self-preservation hydrate.

Fig. 4 On the left is transparent container with a fragment of the gas hydrate. The temperature sensor are visible under the cap. On the right is the temperature graph, B1 and B2 - data upper and lower temperature sensors, M - water temperature outside the container

ACKNOWLEDGMENTS This study was supported by Program no. 23 & 27 of Basic Research of the Presidium of the Russian Academy of Sciences, by the Foundation for the Assistance of Lake Baikal’s Preservation, and by Government Contract no. 16.420.11.0013.

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Geometric Analysis of a Cluster of Mud Volcanoes and Associated Mud Chambers Description of Shallow Fluidization Zones Dupuis Matthieu, Vendeville Bruno Université des Sciences et Technologies de Lille1, Laboratoire Géosystème, UMR CNRS 8217, 59655 Villeneuve d’Ascq cedex, France [email protected], [email protected]

Imbert Patrice Total, 64000 Pau, France [email protected] ABSTRACT We investigated the architecture of mud volcano systems using a 3-D seismic block that covers an actively growing anticline in an oil and gas bearing basin. Our geometric analysis helped us constrain the emplacement of the mud volcanoes and propose a mechanism for such an emplacement. For some authors, methane gas is inherently involved in the formation of all mud volcanoes (Etiope & Martinelli, 2009). According to the literature, even the more recent, mud volcanoes are described as surface features of a larger system in which mud originates deep overpressured levels, then migrates upward. Our work brings a new hypothesis on the role of fluids and their migration based on the observation of sub-surface fluidization zones interpreted as shallow mud chambers. A series of nine mud volcano systems ranging from Late Pliocene to present-day was observed on the seismic survey. Their morphology ranges from flat mud pies to well-developed cones, having typical diameters of 2 to 5km. Several of the inactive volcanoes allow visualizing the underlying plumbing system, which commonly consists of a shallow collapsed zone corresponding to the former mud chamber, and whose volume roughly matches that of the corresponding mud volcano. The collapse can occur either along normal faults dipping towards the axis of the volcano, or as smooth deflation and subsidence of the roof. In one example, the visibility is sufficient to allow reconstructing the pre-eruption morphology of the chamber. The evacuation surface is defined as the contact between the truncated level (toplap) of the underlying horizons and the apparent downlap of the overlying reflectors. The series above can be split into a parallel-layered intervals, whose reflections can be compared and projected directly into the regional background series, and a lenticular body that appears to wedge out radially into a very thin sedimentary interval (one or a few seismic phases, i.e. thinner than 50 m). Assuming that the interval of the mud chamber was deposited as parallel continuous hemipelagites, as can be observed over the whole area outside the mud volcanoes, the chamber is restored as a lenticular zone about 2 km in diameter and 500 m in thickness. The chamber in that particular case is completely depleted. The lenticular body is interpreted as a succession of mud volcanic flows radiating from a central vent; the first flows now dip inwards because of the progressive subsidence of the chamber. The fact that the whole body wedges out into a very thin interval is interpreted to indicate that the emplacement occurred over a short period after the whole chamber had been liquefied. The maximum diameter (equatorial plane) of most mud chambers occurs at the same stratigraphic level, although the timing of mud volcanic eruption varies from one volcano to the other. This is interpreted to reflect a stratigraphic constraint on the area of maximum liquefaction, while episodes of mud volcanic “eruptions” would rather reflect the time at which the liquefied chamber became too wide to continue to effectively support its overburden. The eruption process would in that case be related to a problem of roof resistance, rather than overpressure in the chamber by fluids migrating from deeper series. 116

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VII: September 3rd (09:30-09:50) REFERENCES Etiope, G. and G. Martinelli (2009), “Pieve San Stefano” is not a mud volcano: Comment on “Structural controls on a carbon dioxide-driven mud volcano field in the Northern Apennines” (by Bonini, 2009), Journal of Structural Geology 31 (2009) 1270-1271. Bonini, M. (2009), Structural controls on a carbon dioxide-driven mud volcano field in the Northern Apennines (Pieve San Stephano, Italy): relations with preexisting steep discontinuities and seismicity, Journal of Structural Geology 31, 44-54.

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Turning Stratified Fine-grained Sediment into Homogeneous Mud: the Role of Gas Patrice Imbert1, Matthieu Dupuis1,2, Viviane Casenave1 1Total CSTJF, 64000 Pau, France [email protected], [email protected], [email protected]

Bruno Vendeville2 2

Université de Lille [email protected]

Francis Odonne Université de Toulouse [email protected] ABSTRACT Seismic observations from various sedimentary basins evidence a coincidence between remobilization of fine-grained sediment and the presence of gas at shallow levels nearby. A series of examples will be presented, encompassing a full spectrum from mud volcanoes and mud pies to subsurface evacuation craters and homogeneous bodies interpreted as failed mud chambers. Comparisons between the morphologies observed for the various examples on the one hand, and between the emplacement process deduced from these morphologies on the other, suggest that in many cases gas plays an active part in fine-grained sediment remobilization. THE SPECTRUM OF MUD REMOBILIZATION SYSTEMS Remobilization of fine-grained sediments occurs in a variety of manners, the most classical being mud volcanism. It must be made clear, though, that the term itself encompasses a variety of physical behaviors, from the buildup of real (mud) stratovolcanoes made up of stacked individual flows, up to the concentric growth of thick mud pies by radial crushing of their walls. Other types of remobilization have been described over the last decade, in particular large (several tens of km²in diameter) crater-like features (Riis et al., 2005; Imbert and Ho, 2012; Imbert et al., 2014).

Fig. 1: Cross-section of a 5-km by 8-km crater of the South Caspian Basin. Arrows denote seismic evidence of gas pools at shallow levels (cf. Imbert et al., 2014) 118

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VII: September 3rd (09:50-10:10) The study reported by Dupuis et al. (this GIMS12 conference) shows that mud volcanism in some cases records the geologically rapid vertical transfer of a multi-km3 body upwards through its overburden to the seafloor, while the emitted fluids are regionally known to come from much deeper levels. The craters mentioned in the previous paragraph similarly show evidence of material removal below overburden. In the case shown by Riis (2005), the removed material can be found above its source, slightly offset downslope by mass transport. In the other two cases, no evidence of the disappeared material could be found, suggesting that it may have been evacuated as dilute sediment plumes in sea water. All these examples record the transformation of an originally layered sediment body into a mass fluid enough to be expelled through sub-seismic features, likely vertical conduits. Field observations of mud volcanoes show that most of the time they expel disorganized mud breccia, or simply fluid mud. This raises the issue of the way layered sediment can be turned into homogeneous mud. An additional observation of interest is that most of the features described here sit atop anticline crests in hydrocarbon-bearing basins. MUD CHAMBERS Observations from the South Caspian Basin (Dupuis, this conference) and West Africa (Casenave, 2011) show evidence of seismically homogeneous masses of sediment, with volumes on the order of 1 km3, scattered in the sediment pile. Their limits cross-cut the stratigraphy around without any specific reflection associated, their envelope ranges from bowl-shaped to Christmas-tree-shaped. One such homogeneous, reflection-free mass shows in its middle a layered block that matches the seismic succession of reflections observed several hundred meters higher up near the top of the mass, suggesting that it is a stoped block from the roof of a plastic volume (Fig. 2).

Fig. 2: Seismically transparent mass (interpreted in blue on the right part) with a stoped block in the middle: a mud volcano that never made it?

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By analogy, the other transparent masses of the area are interpreted as mud chambers or failed mud chambers, i.e. km3-scale masses of homogenized sediment that may remain plastic, ready to be expelled to the surface, or that once became plastic enough to be homogenized and have now stabilized. A number of the latter features show evidence for limited transfer of material upwards, suggesting that there may have been segregation inside and expulsion of a small part of the chamber while the rest was fossilized. OBSERVED ASSOCIATION WITH GAS AND PROPOSED PROCESS The association of mud remobilization with gas expulsion is nearly systematically observed on active systems (Fig. 1, Fig. 3, full review in Etiope et al., 2009), suggesting that gas may well be an active part of the process. In a majority of the cases described above, seismic indications of shallow gas can be seen near the locus of sediment remobilization or removal, either laterally (Riis et al., 2005) or immediately below or above (Fig. 1, Imbert et al., 2014). In the case documented offshore Australia by Imbert and Ho (2012), the presence of gas at the time of remobilization was inferred from the regional knowledge of the petroleum system and from comparison with modern analogues where gas hydrates have been sampled in geometrically similar situations (George and Cauquil, 2007, Sultan et al., 2010). The transparent body of Fig 1 and several tens of similar features offshore W Africa develop above anticline crests in an oil and gas province.

Fig. 3: A bursting gas bubble on a small gryphon in the Gobustan area, Azerbaijan. Bubble diameter ca. 15 cm Recent experiments by Sultan et al. (2012) have shown that decreasing the confinement pressure of mud samples previously saturated with gas-saturated water caused gas exsolution of course, but also a loss of resistance to shear in the sediment. This process, monitored in the laboratory with relatively low confining pressures (a few bar) is hypothesized to be the cause of mud liquefaction at depth when the overburden pressure is decreased on gas-bearing fine-grained strata. This can for instance occur in the following cases: growth of a submarine anticline, crestal erosion of an anticline on land or mass failure in any setting.

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REFERENCES Aiello, I.W., C. Lazar, M. Zabel, K.-U. Hinrichs, A. Teske, T. Goldhammer, M. Elvert, V. Heuer (2013), “An expanded seafloor in the brine lake of the Urania Basin: a new deep-water marine environment”, abstract of the 30th IAS Meeting, Manchester, UK, September 3-6, 2013. Casenave, V. (2011). “Les chambres de boue”, internship report, Total unpublished document Dupré, S., J. Mascle, J.-P. Foucher, F. Harmegnies, J. Woodside, C. Pierre (2014), “Warm brine lakes in craters of active mud volcanoes, Menes caldera off NW Egypt: evidence for deep-rooted thermogenic processes”. Geo-Marine Letters, 34 (2-3), 153–168 Etiope, G., A. Feyzullayev, C.L. Baciu, C.L. (2009), “Terrestrial seeps and mud volcanoes: A global perspective of gas origin”, Marine and Petroleum Geology 26, 333-344 George, R.A. and E. Cauquil ( 2007). “AUV Ultra High-Resolution 3D Seismic Technique for Detailed Subsurface Investigations”, Offshore Technology Conference, Houston (2007), paper # OTC 18784 Imbert, P. and S. Ho (2012), “Seismic-scale funnel-shaped collapse features from the Paleocene-Eocene of the North West Shelf of Australia”, Marine Geology, 332-334, 198–221 Imbert, P., B. Geiss and N. Fatjó de Martín (2014) “How to evacuate 10 km3 of mud: saturate with gas and decrease the pressure!”, Geo-Marine Letters, 34, 199–213 Riis, F., K. Berg, J. Cartwright, T. Eidvin and K. Hansch (2005), “Formation of large, crater-like evacuation structures in ooze sediments in the Norwegian Sea. Possible implications for the development of the Storegga Slide”, Marine and Petroleum Geology, 22 (1–2), 257–273 Sultan, N., B. Marsset, S., Ker, T. Marsset, M. Voisset, A.-M. Vernant, G. Bayon, E. Cauquil, J. Adamy, J.-L. Colliat, and D. Drapeau (2010), “Hydrate dissolution as a potential mechanism for pockmark formation in the Niger delta”. Journal of Geophysical Research 115 (B08), doi: 10.1029/2010JB007453

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Oxygen and Sulphur Isotopic Compositions of Authigenic Gypsum from Methane Seeps of the Southwest African Continental Margin Catherine Pierre, Sorbonne Universités, Université Pierre et Marie Curie, LOCEAN-IPSL, 4 Place Jussieu, 75252 Paris Cedex 05, France., [email protected] Jérôme Demange, Sorbonne Universités, Université Pierre et Marie Curie, LOCEAN-IPSL, 4 Place Jussieu, 75252 Paris Cedex 05, France., [email protected] ABSTRACT The southwest African continental margin is a well known area of active methane seeps that are related to high deposition rates of organic-rich sediments where intense methanogenesis occur in the subseafloor environment. The wide pockmark structures offshore Gabon and Congo at water depths of 3000-3500 m are associated with authigenic carbonates and often with gas hydrates accumulations. In a previous study dedicated to authigenic carbonates from these methane seeps, Pierre et al (2012) demonstrated that these carbonates were clearly derived from the anaerobic oxidation of methane (AOM) that was coupled with the reduction of sulphate, both processes being mediated by microbial activity. These pockmarks are also characterized by the presence of abundant chemosynthetic benthic fauna of bivalves and tubeworms that represent important actors for bioirrigation at the seafloor. The organic-rich sediments are totally anoxic up to the surface and contain huge H2S concentrations that justify the frequent occurrence of pyrite. There is also abundant authigenic gypsum that occur as hyaline prisms more or less elongated or as dull prismatic or lenticular crystals. Pierre et al (2012) interpreted these gypsum crystals as the product of oxidation of sulphide (pyrite or H2S) by oxygenated bottom water during bioturbation /bio-irrigation by benthic organisms. The oxygen and sulphur isotopic compositions of pyrite and gypsum from the sediments of three pockmarks (Worm Hole, Deep Hole, Regab pockmark) have been performed to verify this interpretation of the origin of gypsum from methane seeps environments. The oxygen isotopic composition of gypsum from 9 different sedimentary samples varies widely (+1.6 < d18O ‰ V-SMOW < +7.9). These values are lower than the value characteristic of the sea-water sulphate (d18O = +9 ‰ V-SMOW), which indicates that the sulphate of gypsum is issued partly from sulphide oxidation, either by dissolved oxygen or by oxygen of water. The sulphur isotopic composition of pyrite from 8 different sedimentary samples varies within a narrow range (-50.4 to -44.9 ‰ V-CDT) that indicates a strong isotopic fractionation during the bacterial reduction of the sea-water sulphate (d34S = +20‰ V-CDT). The sulphur isotopic composition of gypsum displays very large variations (-38.8 < d34S ‰ V-CDT < +10.9) with values intermediate between those of pyrite and sea-water sulphate. Overall, these results demonstrate clearly that these authigenic gypsum crystals are issued from the oxidation of sulphide close to the seafloor, more probably H2S that is easily available in pore solutions and is also used by the chemosynthetic organisms. Moreover, there seems to be a significant enrichment in 34S in gypsum from sediments containing gas hydrates compared to gypsum from sediments devoided of gas hydrates. REFERENCE Pierre C, Blanc-Valleron M-M, Demange J, Boudouma O, Foucher J-P, Pape T, Himmler T, Fekete N, Spiess V, 2012. Geo-Mar Lett 32 :501-513 122

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Active Methane Seep Events Offshore Southwestern Taiwan Inferred from 230Th-Dated Authigenic Carbonate Chuan-Chou Shen and Yi-Chi Chen Department of Geosciences, National Taiwan University, Taipei, Taiwan ROC [email protected]

Yun-Shuen Wang and Po-Chun Chen Central Geological Survey, MOEA, Taiwan ROC

Horng-Sheng Mii Department of Earth Sciences, National Taiwan Normal University, Taipei, Taiwan ROC

Shih-Wei Wang National Museum of Nature Science, Taichung, Taiwan ROC

Pei-Ling Wang and Saulwood Lin Institute of Oceanography, National Taiwan University, Taipei, Taiwan ROC

ABSTRACT Formation of carbonate concretions has been suggested to be enhanced with gas hydrate decomposition and considered to be a chronometer of past methane seep events. Using 230Th dating techniques, we determined formation ages of authigenic carbonates collected from gas hydrate sites offshore southwestern Taiwan, including Yuan-An Ridge, Good Weather Ridge, and 96 Mud Volcano Group. These carbonates deposited at three time intervals of 50-80, 150-200, and 350-400 thousand years ago (ka). Most of them intensively formed during 150-200 ka, equivalent to Marine Isotope Stage (MIS) 6, the penultimate glacial time with sea level about 80-100 m lower than present. Our results implied that the decreased sea floor pressure shoaled the base of gas hydrate stability and triggered massive dissolution of gas hydrates. Depleted carbonate δ13C values are from -48‰ to -44‰, suggesting that the carbon source could be from both oxidized methane (δ13C = -100 to 30‰) and hydrocarbons (δ13C = -20 to -30‰). 18O data of the authigenic carbonates range from 3 to 7‰, expressing a mixture of two sources of seawater (δ18O = 0 to 1‰) and decomposition of 18O-enriched gas hydrate.

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Iodine as an Indicator of Deep Marine Diagenesis: Pore Water Chemistry of Sediments Associated with Methane Generation in Coalbeds of the Shimokita Peninsula. Glen Snyder Gas Hydrate Research Laboratory, Meiji University, Tokyo, Japan [email protected]

Hitoshi Tomaru Chiba University, Chiba Japan [email protected]

Chiaki Toyama JAMSTEC, Yokosuka, Japan [email protected]

Yasuyuki Muramatsu Gakushuin University, Tokyo, Japan [email protected] ABSTRACT Elevated concentrations of dissolved iodide in the pore waters of marine sediments have long been considered to be indicative of active release of iodine from marine organic matter. Dissolved hydrocarbons, particularly methane, are often associated with high iodine content, such that it is presumed that the processes which govern deep methanogenisis are also associated with the breakdown of iodine-rich organic substances. Not much is known about this process, beyond relatively shallow sediment sampling. Iodine-129 analyses have consistently suggested that both the iodine and associated methane in the upper few hundred meters of marine sediments are consistently older than shallow hosts sediments. This is not surprising given the observed concentration gradients and stable isotope results which frequently suggest that methane associated with shallow sediments is often at least partly of thermogenic origin and is actively diffusing upward as host sediments are buried. The Shimokita Peninsula coalbeds are presently situated beneath more than 1500m of marine sediment offshore the northeastern coastline of Japan’s Honshu Island. Using results from a single hole drilled initially during the Chikyu Shakedown cruise and subsequently drilled to more than 2500 mbsf during IODP Expedition 337, we compare pore water profiles for iodide and the other halides, as well as alkalinity. Although the initial drilling showed notable increases in iodide and alkalinity in the upper 300 meters of the sediment column, concentrations are quite low, similar to seawater in the deep sediments and coalbeds. Our results suggest that active methanogenesis coupled with rapid burial established high concentrations observed today at about 300 mbsf. The coalbeds in their current setting are not actively releasing iodine or dissolved organic carbon, and the pore water composition reflects seawater perhaps from even deeper sediments that are poor in organic matter.

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Methane Release from the Seabed and Reliability of the Paleo-Record Kamila Sztybor, Tine L. Rasmussen, Jürgen Mienert, Stefan Bünz and Chiara Consolaro CAGE - Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geology, University of Tromsø, Norway [email protected], [email protected], [email protected], [email protected], [email protected] ABSTRACT A suite of cores collected from the Vestnesa Ridge from an area with several active methane gas flares is currently investigated. The Vestnesa Ridge (west of Svalbard at ~79o N) is a 100km long sediment drift in the Fram Strait and represents one of the northernmost gas hydrate provinces that exist along the Arctic continental margins. Sediment cores have been collected within and outside one of the active pockmarks. The main purpose of the study is to investigate the frequency of methane emissions from the seafloor through time in relation to past climate change. Pockmark cores are characterized by a strong hydrogen sulfur odor in the upper part with gas bubbles and carbonate rocks present in the sediment. Numerous large bivalve shells in the cores probably mark the time when the seep site became more active. The lithological log, X-ray, magnetic susceptibility and numerous AMS (accelerator mass spectrometer) dates were used to constrain the age model and for high-resolution inter-core correlation. The magnetic susceptibility record of the control core shows a pattern with values typical for the western Svalbard margin (Jessen et al., 2010) and that it covers the last ca 30,000 years. The cores from the active seep area show almost constant values of very low magnetic susceptibility. The seeping of methane clearly destroyed the signal. Other proxies used in order to reconstruct the dynamics of changes of bottom water properties as well as North Atlantic hydrography were oxygen and carbon isotopes of benthic and planktonic foraminifera, assemblage counts and content of ice-rafted debris. Benthic foraminifera show low δ13C values within several intervals, indicating increased methane flux from the seafloor. Carbon isotope values measured in planktonic foraminifera shells are also extremely low (<-10 ‰), which can be caused by coating of AOM (Anaerobic oxidation of methane)-derived carbonates (authigenic overgrowth). This precipitation process affects the outcomes of AMS dating. Radiocarbon dates are in chronological order downcore, but they deviate from the age model based on the lithological log. Our results suggest that radiocarbon dates measured in planktonic foraminifera and bivalve shells are approximately 2000 cal years too old. To construct the correct age model for a core from the seep site, it must have undisturbed, recognizable lithological units and a control core from outside the seepage area is needed for correlation. REFERENCES Jessen, S.P., Rasmussen, T.L., Nielsen, T., Solheim, A., 2010. A new Late Weichselian and Holocene marine chronology for the western Svalbard slope 30,000 - 0 cal years BP. Quaternary Science Reviews 29, 13011312. doi: 10.1016/j.quascirev.2010.02.020.

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Evolution of Hydrocarbon Seepage Mechanisms and Flux through Time Deduced from the Vertical succession of Methane-Derived Authigenic Carbonates: A Case Study from the Vocontian Basin, SE France Jean-Philippe Blouet Department of Geosciences, University of Fribourg, Switzerland [email protected]

Patrice Imbert Total-CSTJF, France [email protected]

Anneleen Foubert Department of Geosciences, University of Fribourg, Switzerland [email protected]

Sutieng Ho School of Earth and Ocean Sciences, Cardiff University, United Kingdom Cenozoic Geoscience Editing and Consulting, Australia [email protected] ABSTRACT Fluid seepage is an important phenomenon occurring in different marine settings and can include leakage of hydrocarbons from marine sediments. The precipitation of authigenic carbonates associated with seepage of methane-rich fluids is the result of the anaerobic oxidation of methane coupled with sulfate reduction. The morphology and geometry of methane-derived authigenic carbonates (MDAC) is strongly influenced by the processes and style of methane seepage. In order to establish a potential link between the mechanisms and fluxes of seepage and the geometric character of MDAC, the Aptian/Albian Marnes Bleues Formation, well-exposed in the Vocontian Basin, SE France, has been investigated in detail. The Marnes Bleues Formation in the Vocontian Basin is characterized by several types of carbonate concretions, which have been classified based on their morphology (Fig. 1) and mapped over an area that is 150 m in vertical and 200 m in lateral extent. A detailed petrographic study of the sampled carbonate concretions has been performed using classic microscopy, SEM, fluorescence and cathodoluminescence microscopy. Stable isotope analyses have been measured to trace the diagenetic pathways and the fluids involved in carbonate precipitation. Mapping and sampling of the carbonate concretions distinguished two main morphologies: 1) sub-spherical nodules and 2) complex ramified carbonate tubes characterized by a central conduit. The carbonate concretions are either aligned along beds, gently crossing stratigraphic layers or clustered in vertically stacked groups. Stable isotope analysis provides evidence that concretions are depleted in δ13C (with lowest values of - 41‰PDB), and slightly enriched in δ18O (as high as 1‰PDB) in comparison to normal marine carbonates. These values imply that anaerobic oxidation of methane is most likely responsible for the precipitation of the carbonate concretions that can thus be interpreted as MDAC. Based on the amount of MDAC quantified through mapping, it is possible to calculate the hydrocarbon flow necessary to precipitate the observed quantity of carbonate concretions. Preliminary calculations indicate an estimated flux of approximately 10 -2 mol/m²/year. 126

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session VIII: September 3rd (11:50-12:10) This value is far below the quantity of methane measured in modern seep environments, suggesting that only a certain quantity of methane has been involved in the formation of MDAC. However, we are aware that mapping is only based on the exposed sections and that 3D analysis of the whole outcrop may reveal a larger quantity of MDAC. The carbonate concretions aligned along specific beds may indicate a widespread and relatively short methane venting event, while the vertically stacked succession of MDAC clusters could be the result of a multi-phase but focused seepage mechanism.

Figure 1. Different morphologies of MDAC tubes. A) Small tube showing complex branching. B) Slab of broken tubes right above a cluster of tube. C) Hemispheric dome made of nodules. D) Lenticular cluster of tubes. E) Limestone bed showing a protruding root. F) Large tube.

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Numerical Modeling of the Co-Existence of Dissolved and Gaseous Methane in the Blake Ridge Site- Implications for Gas Hydrate Accumulation Dynamics Ewa Burwicz, Lars Ruepke and Klaus Wallmann GEOMAR Helmholtz Centre for Ocean Research Kiel [email protected], [email protected], [email protected] ABSTRACT This study provides new insights on the complex three- phase system of the Blake Ridge site, offshore South Carolina. A new numerical reaction-transport model has been applied to the gas hydrate- bearing marine setting where co- existence of dissolved and gaseous methane within the Gas Hydrate Stability Zone (GHSZ) has been reported (Guerin et al., 1999, Taylor et al., 2000). An indication for high methane fluxes associated with the presence of cold seeps and venting sites has also been suggested (Paull and Matsumoto, 2000). Based on our numerical simulation accounting for sediment deposition and compaction, microbial processes of methane oxidation via sulfate reduction (AOM), methanogenesis and organic matter degradation, we would like to present a new scenario of gas hydrate crystallization within the time frame of a basin history. MODEL DESCRIPTION In order to investigate dynamic processes associated with gas hydrate and free gas migration and accumulation within sedimentary basins, we have designed a numerical Gas Hydrate 3- Phase Advanced Dynamics platform (GH- 3PAD) which resolves for marine sedimentation and associated fluid expulsion as well as porosity reduction, biogenic methane formation, and bio-chemical reactions which affect the pool of methane available for hydrate formation. This numerical model tracks chemical concentrations of dissolved in pore fluid species (CH4, SO4, DIC) as well as solid organic carbon particles (POC) and gaseous methane which are coupled to the rates of chemical reactions (organic matter decay, methanogenesis, sulfate reduction and methane oxidation). Gas hydrate crystallization can occur via thermodynamic or kinetic- based processes. An external, deep source of methane has been incorporated into the model to investigate the sensitivity of the system to high velocity methane fluxes which, eventually, result in the seafloor venting that has been confirmed by seismic data and direct observations on site. SITE CHARACTERIZATION Blake Ridge, offshore Carolina site is one of the most studied gas hydrate provinces worldwide. It is characterized by gas hydrate concentrations usually falling into range of 4 - 7 vol. % and moderate methane fluxes often associated with fault structures (Paull et al., 1996, Taylor et al., 2000). Organic carbon content at the sediment top oscillates around 1.5 wt. % and provides an important source of carbon available for biodegradation (Paull et al., 1996). The important feature of this region is the commonly observed depth discrepancy between thermodynamically defined Gas Hydrate Stability Zone (GHSZ) and the presence of Bottom Simulating Reflectance (BSR) which marks the upper-most location of free gas in sediment column. The overlapping depth of these two distinct zones mentioned above, covers from 20 up to 50 m of sediments which show an evidence of bearing both gas hydrate (enhanced non-elastic properties of sediments) and free gas (BSR position) phases (Guerin et al., 1999). 128

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IX: September 4th (08:30-08:50) FREE GAS MIGRATION IN SHALLOW SEDIMENTS Accounting for the free gas and gas hydrate co- existence within the GHSZ brings challenges to the modeling of such dynamic marine system. Clearly observed methane escape throughout the seafloor implies a presence of a gas phase migrating through underlying sediments. The rate of free gas – gas hydrate reaction is still highly debatable and depends on several factors, such as: the volume of free methane gas migrating upwards and its velocity, free gas bubble size and its availability to react with water and form hydrates, potential formation of conduit- like migration pathways, direct physical contact between free gas and water phase (no gas hydrate layer buffering potential reactions), etc. It has been also suggested that the gas hydrate formation from free methane gas might require a transition state of methane dissolution into the liquid phase which enables further gas hydrate crystallization. During the conference, we will present several numerical modeling scenarios that resolve for gas phase migration within shallow part of marine sediments lying within the Gas Hydrate Stability Zone. CONCLUSIONS Using an example of the Blake Ridge site, offshore Carolina, we examine the dynamics of a complex three-phase system including dissolved and gaseous methane and gas hydrate accumulations. The special focus of this study is to resolve for kinetically vs. thermodynamically driven processes associated with gas hydrate formation in shallow marine sediments where the co- existence of dissolved and free methane had been confirmed. REFERENCES Guerin G., Goldberg D., Melser A. (1999), “Characterization of in situ elastic properties of gas hydrate-bearing sediments on the Blake Ridge”, Journal of Geophysical Research 104 (8), 17,781 - 717,795. Paull C. K., Matsumoto R. (2000), “1. Leg 164 OVERVIEW”, Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 164. Paull C. K., Matsumoto R., Wallace P. J. (1996) 9. Site 997, Shipboard Scientific Party. Proceeding of the Ocean Drilling Program, Initial Reports, Vol. 164. Taylor M., Dillon W., Pecher I. (2000), “Trapping and migration of methane associated with the gas hydrate stability zone at the Blake Ridge Diapir: new insights from seismic data”, Marine Geology, 164: 79 – 89.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IX: September 4th (08:50-09:10)

Geological Processes Affecting the Thermal Structures of Shallow Seafloor: An Example from offshore SW Taiwan Liwen Chen, Wu-Cheng Chi, Yu-Sian Lin, Shao-Kai Wu Institute of Earth sciences, Academia Sinica, Taiwan [email protected], [email protected], [email protected], [email protected] Char-Shine Liu Institute of Oceaography, National Taiwan university, Taiwan [email protected] Yunshuen Wang Central Geological Survey, Ministry of Economic Affairs, Taiwan [email protected]

ABSTRACT Fluid migration pattern is important for understanding the structural features of a mountain belt and for hydrocarbon exploration. However, these patterns are difficult to measure on the seafloor, so we have to derive the thermal models from other approaches. Using phase properties of the gas hydrates, we studied the thermal patterns offshore southwestern Taiwan. Seismic explorations in this region showed wide spreading bottomsimulating-reflectors (BSR), which are interpreted as the bottom of the gas hydrate stability zone. It provides us a good opportunity to study possible fluid flow patterns at several hundred meters subbottom depths of the marine sediments. First, we used BSR-based geothermal gradient patterns to derive vertical fluid flow models by analyzing the Péclet Numbers. We found the regional 1-D fluid flow rates ranges from 6 cm/yr to 43 cm/yr, including several prospect sites for gas hydrate exploration. Next, we modeled 2-D and 3-D steady state temperature fields from Pecube in the regions of the deformation front, active and passive margin, to account for the thermal effects by comparing the temperature discrepancies from BSR and our models. Then we proposed several important thermal effects to interpret our regional studies results. We successful used the temperature discrepancies to reduce the regional topography effects, and proposed some possible models of the thrust faulting and the fluid migration in Yung-An Ridge and the frontal thrust regions. Then I used the heating and cooling effects in diapir of the lower Fangliao Basin and the Formosa Ridge to describe the sedimentation and erosion, moreover, I interpreted several steps of the evolution on temperature fields for the mass transport deposits. We believed these temperature simulations told us lots information about the fluid migrating or its thermal effects, thus we could acquire more correct regional heat flow information to monitor or detect our future resources.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IX: September 4th (09:10-09:30)

Meso-scale Modeling of Methane Hydrate Dissociation in Porous Media by using Regular Arrays Wu-Yang Sean Department of Bioenvironmental Engineering, Chung-Yuan Christian University, Taiwan [email protected] Ren-Yu Ye and Ray-Quan Hsu Department of Mechanical Engineering, National Chiao Tung University, Taiwan [email protected], [email protected]

ABSTRACT Finite volume method with unstructured mesh were constructed in a three-dimensional, porous media by assuming the media spherical type. For the convection–diffusion equations for momentum, mass, and temperature, a third-order up-winding scheme and a second-order central differencing scheme were adopted to approximate the convection and the diffusion terms in non-equilibrium state, respectively. The time differential terms were discretized by a second-order explicit scheme. At the surface of MH, the model reported by Sean and Sato(2005) has been employed. The scheme of CFD has been examined by comparing to the Sherwood number of spherical mass transfer coefficient, ex. Ranz-Marshall (1952), Rowe (1965), and Whitaker’s (1972) correlations at Re=155 and Sc=1965. The results of our work are in good agreement with these correlations. Then, Two regular-arrays of simulating methane-hydrate sediment with different porosities were studied by composing depressurization(5MPa) and heat stimulation(15℃). The production rate in two cases are compared. Nest phase we will conduct the experiments to verify the modeling and analyze the effect of porosity, temperature and pressure. INTRODUCTION The production rate of methane hydrate(MH) in the marine sediments is what we concern in estimating the field-scale production wells. The depressurization and heat stimulation are regarded as effective methods in exploitation. As for estimation of dissociation rate of MH, Kim(1987) and Bishnoi have established a fundamental empirical correlation of methane gas dissociated from the bulk slurry methane hydrate. Sean and Sato(2005) conducted a series experiments, and estimated the intrinsic dissociation rate in the water flow by CFD methods. This model has been verified either in Hydrate-Lw domain or Vapour-Lw phase. In the in-situ sediment, MH bearing sediment are composed of water, methane gas, sandstone and so on. The dissociation phenomena are very complex including mass, heat transfer, and mechanical behavior inside the rock. Many researchers have established field-scale models to simulate the production rate of MH by using various methods [1-5]. In this study, we propose a meso-scale modeling by using regular arrays to simulate the detailed dissociation performance of methane hydrate existing in sediment, and estimate the production rate affected by the porosity, temperature, and pressure in the non-equilibrium state. 131

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IX: September 4th (09:10-09:30) Theoretical Treatment: A Dissociation Model Formulation of the Dissociation Rate Equation In this study, it is assumed that the dissociation flux ( F1 ) is proportional to the driving force, the free energy difference(  ), expressed as

F1  kbl 

(1)

where k bl is the rate constant. According to the work by Sean and Sato[6], k bl is listed below:

k bl  3.89  10 12 exp( 

98300 ) RT

(2)

Then  can be approximated by

  RT

x eq xI

 RT

C Hsol CI

(3)

where x eq mole fraction of methane in the aqueous solution at equilibrium with hydrate, to that in the ambient aqueous solution at the surface of the hydrate x I . Basic transport equations Incompressible flow around a single MH pellet is governed by the continuity and the Navier-Stoke’s equations. The advection-diffusion equations of non-conservative type for mass concentration C and temperature T are also solved.

u  0



(4)



 u 1 T    uu   P    u  u   w2 g t Re Fn C 1  u  C   2C t ReSc T 1  u  T   2T t RePr

(5) (6) (7)

where the viscosity, diffusivity and thermal conductivity of pure water included in non-dimensional  Ud     parameters the Reynolds number, Re    , the Schmit number, Sc    and the Prandtl number  D      Pr    L

  , which are expressed as functions of temperature and are renewed every computational 

time step are summarized in Eqs. 4-7. U and d is the inlet average velocity and diameter of MH pellet.  T   8.8285  10 10 T 2  5.3886  10 7 T  8.3104  10 5 DT   1.2398  10

12

T  6.7677  10 2

 L T   0.48784  ln T   2.17384

where thermal diffusivity of pure water  L 

10

T  9.4190  10

8

(8) (9) (10)

 L T  is calculated from thermal conductivity  L [8]. W C p

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IX: September 4th (09:10-09:30) The numerical simulation method For the convection–diffusion equations for momentum, mass, and temperature, a third-order up-winding scheme and a second-order central differencing scheme were adopted to approximate the convection and the diffusion terms, respectively. The time differential terms were discretized by a second-order explicit scheme. Pressure and velocity were coupled based on the marker and cell (MAC)–type fractional step method. Incompressible flux at each cell face, originally introduced in Rhie and Chow was taken into account in the pressure calculation for the numerical stability of the present collocated-grid method. The following physical properties are used for the CFD calculations[12]: C HSOL T , P   C HSOL  old (T , P )  C GSOL Peq  C HSOL old Peq (11)

C HSOL old T , P   1.0  10



4

 1.0  10

  8



 





P  2.23  10 4 exp 0.0317 T 



CGSOLT , P   exp  152 .777  7478 .8 T  20.6794 ln T  0.75316 ln(10 P) 5

Peq  exp( a  b / T ) 10 6 ( a  32 .818 , b  8728 )

(12) (13) (14)

where C GSOL is the solubility of methane gas in water, and Peq means the equilibrium pressure of hydrate and liquid phase. Mass transfer of CO2 To rewrite Eq. (3), the boundary condition for the methane concentration at the surface of the hydrate can be given by

kbl RT ln(

C HSOL C  C )  DC  D I CI hI

(15)

where D and C are, respectively, the diffusion coefficient and the concentration of methane in the aqueous phase in the vicinity of the surface. CI is unknown and calculated locally at each surface cell, , C’ is the centroid value and CHSOL is the solubility of methane hydrate.

Fig. 1 Schematic image of interface concentration Heat transfer The heat transfer at the surface of CO2 hydrate is given by (16) where

(

, where

is the latent heat of hydrate dissociation) is the rate at which the

latent heat is transferred to the CO2 hydrate by dissociation;

and

in the hydrate and water, respectively. Heat of dissociation per mole hydrate

are the heat conductivities is given by Kuustraa

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IX: September 4th (09:10-09:30) and Hammershaimb[8] as (17) where

is the surface temperature. Then we have

(18) where

and

are the temperatures defined at the centroids of a cell in the aqueous phase and at a

cell in the solid hydrate, respectively; and are the centroids of a cell in the aqueous phase and at a cell in the solid hydrate, respectively. These cells are attached to the hydrate surface, as shown in Figure 2.

Fig. 2 The treatment of heat flow at the surface of MH Besides, the temperature in the pellet is solved by heat conductivity equation. T  2T H t x 2

H 

H  H C p

(19)

is thermal diffusivity of MH. These relative properties of MH are quoted from the

values used in Masuda (2002), which are listed in Table 3.5.1. Table 1 The basic properties of MH

thermal conductivity λ H isobaric specific heat C' p density ρ H

0.393 W· m-1K-1 2010 J·kg-1K-1 -3 2000 kg·m

Boundary conditions and initial conditions There are two types of cells, tetrahedrons and triangular prisms in the present unstructured grid system, as shown in Fig. 3. The prisms are arranged on the pellet and tetrahedrons are applied to the flow field and inside the pellet. The cell density in the wake of the pellet is concentrated to resolve vortex shedding. Upward is the inflow where the parabolic velocity profile for laminar flow is adopted. Downward is the outflow and the zero-gradient Neumann condition is imposed. No-slip condition is used on the sidewall and surface of MH pellet. In particular, one cell-layer of the prisms that attach to the MH surface is divided into 15 very thin layers (VTL) of prisms to resolve thin mass and heat boundary layer for high Schmidt number[9]. Refer to Ayako et al.(2010)[13], the experiments has been conducted by using glass beads with diameter( m ) range from 150~250 to simulate the marine

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IX: September 4th (09:10-09:30)

sediment. The porosities of this case study are 0.512 and 0.507, respectively. The detailed condition has been listed in Table 1. This numerical study is based on these experimental data, and to compare the results affected by the physical conditions.

Fig.3 The total view of mesh and enlargement of one pallet inside Verification Before coupling the surface dissociation model, the CFD code is examined by comparing the empirical correlations of the Sherwood number (Sh) and the drag coefficient (Cd). Since saturated surface concentration is considered here, the computation turns off the surface MH decomposition model. Firstly, the calculated Sherwood number with respect to spherical mass transfer coefficient is compared to Ranz-Marshall (1952), Rowe (1965), and Whitaker’s (1972) correlations at Re=155 and Sc=1965. The computational parameters are as the same as those in the case at T=276.15K as listed in Table 2. Table 2 Result of Sherwood-number verification at Re=155, Sc=1965 and T=276.15K Sherwood number (Sh)

Total mesh no.

Surface mesh no.

VTL no.

RansMarshall

Rowe

Whitaker

CFD

74379 48413

1544 376

15 20

95 95

125 125

140 140

113 116

Results and Discussion In this study, the methane hydrate formed in the porous mediate has been assumed as a regular array with possible porosity 0.512~0.507. The unstructured mesh is shown as Fig. 2. To simulate the in-situ dissociation environments, the computational conditions and measurements of bulk concentrations CX are listed as Table 2. The results show our calculations are in good agreements with the measurements as shown in Fig. 3. The maximum deviation between experiments and calculations in this study is within 10%.

Fig. 4 A schematic representation of particle arrangement with regular array

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IX: September 4th (09:10-09:30)

Fig. 5 A schematic representation of the mesoscale mesh of methane hydrate in porous media (mesh cells are 80696, porosity 0.3692 with unstructured mesh emplying tetra, penta, and hexa)

Fig. 2 Numerical Results of production rate due to depressurization and thermal stimulation CONCLUSIONS Our study established a meso-scale model of methane hydrate dissociation in porous media in non-equilibrium state by using Finite Volume Method and unstructured mesh. Here, we assume the methane hydrate cover in the sandstone homogeneously. Besides, the periodic boundary conditions are composed in the model to simulate the real multi-pellets sediment. The verification is conducted to examine the CFD scheme by comparing the Sherwood numbers. Next, test temperature(15℃) and pressure(5MP) are set to solve the production rate of methane hydrate. The research is still going on to establish the random array of simulating MH sediment, and the experimental set-up, results will be reported in the near future. ACKNOWLEDGEMENT This work was supported by DOIT, Ministry of Science and Technology under contract No. MOST 103-3113-M-033-001.

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IX: September 4th (09:10-09:30) REFERENCES [1] Nicolas Tonnet, Jean-Michel Herri, Methane hydrates bearing synthetic sediments—Experimental and numerical approaches of the dissociation, Chemical Engineering Science, v 64, n 19, p 4089-100, 1 Oct. 2009 [2] Kambiz Nazridoust, Goodarz Ahmadi, Computational modeling of methane hydrate dissociation in a sandstone core, Chemical Engineering Science, Volume 62, Issue 22, November 2007, Pages 6155–6177 [3] Ioannis N. Tsimpanogiannis, Peter C. Lichtner, Parametric study of methane hydrate dissociation in oceanic sediments driven by thermal stimulation, Journal of Petroleum Science and Engineering - J PET SCI ENGINEERING , vol. 56, no. 1, pp. 165-175, 2007 [4] Michael B. Kowalsky, George J. Moridis, Comparison of kinetic and equilibrium reaction models in simulating gas hydrate behavior in porous media, Energy Conversion and Management Volume 48, Issue 6, June 2007, Pages 1850–1863 [5] Y. Masuda, Y. Fujinaga, S. Naganawa, K. Fujita, K. Sato, Y. Hayashi, Modeling and experimental studies on dissociation of methane gas hydrates in berea sandstone cores, Proceedings of Third International Conference on Gas Hydrates, Salt Lake City, Utah, USA (1999) [6] Sean W, Sato T, Yamasaki A, Kiyono F. CFD and Experimental study on Methane Hydrate dissociation Part 1. Dissociation under water flow, AIChE J. 2007; 53: 262-274. [7] Kuustraa VA, Hammershaimb EC. In Charleston WV, editor. Handbook of Gas Hydrate Properities and Occurrence. Lewin & Associates, 1983. [8] Chemical Society of Japan. Kagaku Binran (Handbook for Chemists). Tokyo: Maruzen, 1985. [9] Sloan ED. Clathrate hydrate of natural gases. New York; Dekker, 1998. [10] Jung RT, Sato T, Numerical simulation of high Schmidt number flow on unstructured hybrid mesh. J. Comput. Phys. 2004; 203: 221-249. [11] Handa Y, Compositions, enthalpies of dissociation, and heat capacities in the range 85 to 270 K for clathrate hydrates of methane, ethane, and propane. J. Chem. Thermodynam. 1986; 18(10): 915-921. [12] Kawamura T, Ohga K, Higuchi K. Dissociation behavior of pellet-shaped methane-ethane mixed gas hydrate samples. J. of American Chem. Soc. V, 1987; 17(3): 1645-1653. [13] 中山貴文, 堆積層中メタンハイドレートの賦存表面積の推定, 東京大学大学院 新領域創 成科学研究科 環境システム学専攻, 修士論文, 2007 [14] 福元文子, 多孔質中におけるメタンハイドレート生成に関する数値的・実験的研究, 東京 大学大学院 新領域創成科学研究科 環境システム学専攻, 修士論文, 2010

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IX: September 4th (09:30-09:50)

Efficiency of Depressurization on Gas Production from Class-1 Hydrate Deposits Offshore Southwest Taiwan Cheng-Yueh Wu and Bieng-Zih Hsieh Department of Resources Engineering, National Cheng Kung University, Taiwan [email protected], [email protected] ABSTRACT The purpose of this study was to use numerical simulation to estimate the gas production from depressurization of a class-1 gas hydrate, and to investigate the efficiency of depressurization on a potential hydrate site located offshore southwest Taiwan. The simulator we used was validated from the code-comparison project supported by the NETL. For the case study of K-site, a class-1 hydrate deposit located offshore SW Taiwan, the results of high gas production scenario showed that the total gas recovery factor was 29.7%, in which the free-gas recovery factor was 31%, and 7% of gas hydrate was dissociated in the hydrate zone. The gas rate declined dramatically after 3-year high gas production. For a low gas production scenario, gas can be produced continuously for 20 years; however, the total gas recovery factory was 8.5%. We observed that both top and bottom sides of the hydrate zone will have the decomposition of gas hydrate. For class-1 hydrate deposits, the best completion strategy was to perforate in the upper interval of the gas zone to obtain higher gas recovery. INTRODUCTION Gas hydrates are crystalline which are formed when methane and water mixtures are subjected to high pressure and low temperature conditions. Gas hydrates can be found in subsurface geological environments of deep-sea sediments and permafrost regions, where the presence of in-situ hydrates had been confirmed by many exploration activities around the world. The resources of gas hydrate are vast. Max and Lowrie (1996) estimated that the energy resources of gas hydrates held at least twice the amount of all the fossil fuels on the earth. Taiwan’s hydrate researches pointed out that the hydrate deposits, which was confirmed by the bottom-simulating reflection (BSR), were formed in offshore southwest Taiwan (Liu et. al, 1999). According to their estimates, the hydrate resources in offshore SW Taiwan was about 64 to 77 billion tons oil equivalent. Lin (2011) calculated the initial gas hydrate resources in offshore SW Taiwan are about 2.7 trillion m3. The estimated initially gas hydrate resources showed that there is an opportunity to have this huge gas resources as own energy resources in Taiwan. One of the most important issues about the hydrate resources is how much the methane can be recovered and how to produce methane efficiently. Gas hydrate can be divided into 4 types from class-1 to class-4 (Mordis et al, 2013). Class-1 gas hydrate accumulations have the highest potential to continuously apply large-volume gas production. Class-1 hydrate deposits refer to a hydrate-bearing layer underlain by a free-gas zone. It is possible to use conventional technology of depressurization to produce the dissociated gas from hydrates. The purpose of this study was to use numerical simulation to estimate the gas production from depressurization of a class-1 gas hydrate, and to investigate the efficiency of depressurization on a potential hydrate site located offshore SW Taiwan.

134

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IX: September 4th (09:30-09:50) NUMERICAL MODELING In this study we used the reservoir simulator STARS, which is developed by Computer Modelling Group Ltd dealing with heat transfer, geo-chemical, geo-mechanical, and multiphase fluid flow problems, to study the production of gas hydrate. The STARS simulator was validated from the code-compare project supported by the NETL. We used a pre-processing simulator BUILDER to build the geological model by dividing the structure into grids (Fig. 1). Formation parameters, pressure-volume-temperature (PVT) data, rock and fluid properties, and formation’s initial conditions were assigned sequentially to each grid block, and then the completion (perforation intervals) and operation (production rates and pressure drops) conditions were designed to finish the numerical model (Fig. 1). The changes of reservoir pressure, temperature, saturation due to a production were calculated by STARS simulator. The post-processing simulators (3D and GRAPH) were used to analyze and display calculated results (Fig. 1).

Fig 1. Numerical Modeling Flow Chart The case we simulated was based on the data from K-site, a class-1 hydrate deposite in offshore SW Taiwan. In the case study, 2D radial model with a well drainage area of 1 km2 was designed (Fig. 2). Table 1 showed that the basic reservoir, thermal, and production parameters used in this study.

Fig 2. 2D Radial Model for Class-1 Hydrate Deposits

135

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IX: September 4th (09:30-09:50) Table 1. Basic parameters used in this study Parameter

Value

Unit

Hydrate layer thickness

62.5

m

Gas layer thickness

62.5

m

Hydrate layer porosity

0.4

Gas layer porosity

Value

Unit

Bottom of hydrate layer

160

m

Shale layer permeability

1E-5

md

frac.

Hydrate layer permeability

1000

md

0.4

frac.

Gas layer permeability

1000

md

1

frac.

Pore compressibility

5E-7

1/pa

Grain Specific Heat

1000

J/kg k

Water-Saturated Thermal Conductivity

2.18

W/m k

Grain Density

2600

kg/m3

Dry Thermal Conductivity

2

W/m k

Producing Rate

1000

MSCM/day

Simulation Time

20

years

Kv/Kh

Parameter

The chemical reaction used in this study is: 1 Hydrate  H  6.1water  1CH 4

(1) The capillary pressure (Eq. 2) and relative permeability curves (Eqs. 3 and 4) are designed from Van-Genuchten Equation (Van-Genuchten, 1980) and Stone and Aziz (Stone, 1970; Aziz, 1979) as following:

* where S 

Pcap   po [(S * )1/   1]

(2)

k rG  ( S G* ) n

(3)

k rG  ( S A* ) n

(4)

SG  SirG S A  S irA S A  S irA * * , SG  , SA  , 1 / p o = 8E-5,  =0.45, SirA=0.14, SmxA=1, 1  SirG S mxA  S irA 1  S irA

SirG=0.02, SirA=0.15, n=3. RESULTS AND CONCLUSIONS For class-1 hydrate deposits, depressurization is a useful method to produce natural gas. The production well should be perforated at the upper interval of the gas layer to prevent producing too much water. Natural gas can be produced continuously at 1 MMSCM/day for earlier years, then the gas rate declined dramatically if the minimum bottom hole flowing pressure was assumed to be 9000 kPa (Fig. 3). For the case of maximum gas production rate of 1 MMSCM/day, the cumulative gas production was 8.85 108 SCM with the total gas recovery factor of 29.7%, in which the free-gas recovery factor was 31% and 7% of gas hydrate was dissociated in the hydrate zone (Fig. 4). For another production scenario of maximum production rate of 10 MSCM/day, natural gas can be produced continuously for 20 years, and the reservoir pressure will be maintained above 11,000 kPa. However, the total gas recovery factory was 8.5% for this lower gas production scenario. Based on the simulation results, we observed that the decomposition of gas hydrate will occur at both top and bottom sides of hydrate zone (Fig. 5). Near the hydrate-gas contact, the dissociation was more efficiently than that on the top of the hydrate layer, because the pressure difference in the hydrate zone is larger on the hydrate-gas contact. For class-1 hydrate deposits, the best strategy is to perforate in the upper interval of the gas zone and produce gas from the gas reservoir earlier. When the hydrate dissociated and gas was released, the reservoir pressure was slightly rebuilt to help gas production.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IX: September 4th (09:30-09:50)

(Left) Fig 3. Gas rate, water rate, and bottom hole pressure changing with time in the case of maximum gas production of 1 MMSCM/day. (Right) Fig 4. Hydrate saturation distribution changing with time in the case of maximum gas production of 1 MMSCM/day.

REFERENCES Aziz, K. and A. Settari (1979), Petroleum Reservoir Simulation, Applied Science Publishers. Chung, S.H., Chang, S.F.(2001), “Review and Prospect of Methane Hydrate,” Bulletin of the Central Geological Survey.,(14), 35-82. Computer Modeling Group Ltd (2012), CMG STARS, Calgary, Alberta, Canada. Kvenvolden, K.A., Rogers, B.W.(2005), Gaia's breath—global methane exhalations, Mar. Pet. Geol. 22 (4), 579–590. Lin, T.S. (2011), “The Study of Sedimentary Characteristics and Structure of Formation with Hydrate,” Bulletin of the Central Geological Survey Liu, C.S., Shyu, C.T., Schnurle, P., Fuh, S.C., Hsiuan, T.H. (1999), “Analysis of Exploration Potential of Methane Hydrate in Southwestern Offshore Taiwan,” Conference of Research and Development on Offshore Resource Max, M.D., Lowrie, A.(1996), “Oceanic methane hydrates: a "frontier" gas resource,” J. Pet. Geol. 19 (1)., 41– 56, January. Mordis, G.J., Reagan, M.T., Rutqvist, J., Zhang, K., and Kowalsky, M. (2013), “Modeling Studies of Gas Production From Hydrate Deposits and the Corresponding Geomechanical System Response,” Special Talk at National Cheng Kung University, Tainan, Taiwan. November 2013. Stone, H.L. (1970), “Probability model for estimating three-phase relative permeability.” J. Pet. Tech, 22(2), 214-218. Van Genuchten, M.T. (1980), A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Sci. Soc. Am. J, 44(5), 892-898

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Methane Hydrate Production Top Side Facilities Model: Case Study Indonesia Ardian Nengkoda, Supranto, Suryo Purwono, Imam Prasetyo Gadjah Mada University Indonesia Chemical Engineering Dept., Gadjah Mada University, Grafika Street No. 2, Yogyakarta 55281, INDONESIA [email protected] ABSTRACT During 1999-2005 the Indonesian potential gas hydrate have been reported during “incidental” exploration spread in offshore of Mentawai, Java fore-arc basins and deep water North Makassar basin. In year 2004, a preliminary Indonesian methane hydrate potential deposit calculation were found totally to be around 850 trillion cubic feet (tcf). The study have been conducted with the objective to review most possible production scenario of methane hydrate in offshore sea water Indonesia at Makassar Strait. The five possible scenarios are studied base on their impact: (i) thermal stimulation in which the temperature is increased through heating so that hydrates break into water and gas and the gas is recovered, (ii) depressurization in which the pressure is lowered by pumping out gas at the base of the hydrate that causes dissociation of hydrates into gas and (iii) chemical inhibitor injection where a dissociating agent like methanol is injected into the hydrated sediments that leads to the destabilization and releases gas from hydrates, (iv) fracking and (v) CO2 injection. The economic decision lead to depressurization technique as effective production strategy. The top side production facilities are designed and modeled with scenario of 50 MMSCFD gas productions and the downstream gas utilization are designed to the near by ags processing plant in East Kalimantan. As conclusion, the result of the study can be used as a guide line for the field development.

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How Geometries of Fluid Venting Structures Are Affected by Spatial Variations of Polygonal Fault Patterns Due to Stress Perturbations Sutieng Ho School of Earth and Ocean Sciences, Cardiff University, United Kingdom Cenozoic Geoscience Editing and Consulting, Australia [email protected]

Daniel Carruthers School of Earth and Ocean Sciences, Cardiff University, United Kingdom [email protected]

Patrice Imbert Total-CSTJF, France [email protected]

Joe Cartwright School of Earth and Ocean Sciences, Cardiff University, United Kingdom [email protected]

Jean-Philippe Blouet Department of Geosciences, University of Fribourg, Switzerland [email protected]

ABSTRACT 3D seismic data from Offshore Angola is used to investigate how vertically migrating fluids were influenced by strata-bound arrays of compaction-related normal faults, here called polygonal faults (PFs), which have deformed the Neogene-Quaternary hemipelagites. We discuss the sensitivity of fluid venting style to perturbations in the regional stress state due to salt tectonics, and locally due to salt diapirs and PFs. Regionally isotropic PFs become anisotropic around pockmarks (Fig. 1A), salt stocks and withdrawal basins (Fig. 1B, C). Aligned PF are attributed to local perturbations in a predominantly isotropic stress field. Three main patterns of aligned PFs are presented in this study: 1) ladder patterns composed of long (first-order) and short (secondorder) faults which are orthogonal (Fig. 1A), 2) concentric patterns around pockmarks (Fig. 1A, D) and in salt withdrawal basins (Fig. 1B), and 3) a hybrid form of radial and concentric fault pattern around pockmarks on diapir flanks (Fig. 1C). Fluid venting structures such as methane-derived carbonates and chimneys which are linear in plan view (Fig. 1C) stem from PF intersections (Fig. 1E; Fig. 2A). Chimneys consistently have a linear planform (Fig. 2B) and are interpreted to have formed by hydraulic fracturing. Hydraulic fractures propagated vertically and parallel to faults along the axis of PF grabens. We deduce from the observation that the geometry and location of linear venting conduits are controlled by the location of PF intersections. Most of the fluid venting structures with linear-to-elliptical planform geometries are controlled by the local state of stress around PFs. Our work highlights the sensitivity of polygonal fault systems to perturbations of local tectonic stresses

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session IX: September 4th (10:10-10:30) Poster Session III: September 4th (10:30-11:00)-GIMS12A094 caused by salt withdrawal and diapirism. Both PFs and the location stresses further control the location and geometry of fluid venting structures.

A

C

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Ho et al. (2013) Figure 1. A) Dip map of a horizon within a polygonal fault tier showing PF patterns switching to Concentric faults (CFs) above a pockmark crater. B) Dip map showing concentric first-order PF in a salt withdrawal basin. C) Zoomed amplitude map showing aligned first-order PFs in a withdrawal basin between two salt stocks. Blue and brown arrows denote the locations of linear chimneys and methane-related carbonates respectively. D) Zoomed seismic section bisecting pockmark crater, E) Zoomed seismic line of an elongate fluid pipe between conjugate PFs. Stress ellipses are defined by ratio of Sh (light-blue arrow) and SH (red arrow). Images taken from Ho et al. (2013).

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Ho et al. (2012) Figure 2. Seismic profiles and amplitude maps of numbered horizons showing a single linear conduit originating from the lower tip of a graben in the polygonal fault tier. A) Profiles i and ii are arbitrary lines across and along the axis of the linear anomaly, respectively, and are located in (B) with yellow dashed lines. The shallow vshaped and curved reflections 4 correspond to a linear PHAA on horizon 4 in B. B) Horizons of positive reflections that cross the pipe within the polygonal faulting interval (numbered on A): Horizon 1 shows the pull up zone corresponding to the linear lower amplitude area on the base of the polygonal fault tier. Horizon 2 shows that the linear shape is consistent up to (horizon 3) the top of the fault tier; Horizon 4 shows the linear conduit terminates upward into a high amplitude v-shaped reflection with a linear planform. Horizon 5 shows sub-circular furrows at the present day seabed, above the pipes and at the same location (the undulating lines running WNW–ESE are processing artifacts). Images taken from Ho et al. (2012).

REFERENCES Ho, S., J. A. Cartwright, P. Imbert (2012). “Vertical evolution of fluid venting structures in relation to gas flux, in the Neogene-Quaternary of the Lower Congo Basin, Offshore Angola”, Marine Geology, 332, 40-55. Ho, S., T. D. Carruthers, P. Imbert, and J. A. Cartwright (2013). “Spatial Variations in Geometries of Polygonal Faults Due to Stress Perturbations & Interplay with Fluid Venting Features”, 75th EAGE Conference & Exhibition incorporating SPE EUROPEC 2013, London, United Kingdom, June 10 – 13, 2013.

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Seafloor Fluid Emission in the Khatanga Gulf of the Laptev Sea Kruglyakova R.1, Dachnova M.2., Shevtsova N.1, Mozhekova S.2, Terenozhkin A.1 - SSC «Yuzhmorgeologia». Russia, 353461, Gelendzhik, Krymskaya st, 18, E-mail: [email protected]. 2FGUP VNIGNI, Rosnedra, Moscow ABSTRACT During the period from 2008 to 2010 on Khatanga Gulf of the Laptev Sea the complex of works on an assessment of prospects of oil-and-gas content of the region is executed. The complex of works included seismic, gravi-and magnetometric, litologo-mineralogical works and geochemical researches of sediments for allocation of the anomalies connected with seepage of hydrocarbons from the deep-laying horizons. Geochemical researches included definition of the methane, light (C2-C4) and heavy (C5-C6) homolog’s of methane, CO2, N2, high-molecular hydrocarbons (HMH), organic carbon and bitumoids. Use of geochemistry of HMH is caused by that the composition and the distribution of high-molecular hydrocarbons in unmature organic substance (OS) of the sediments differ from those in mature maternal rocks. The complex of HMU study includes Total Scanned Fluorescence (TSF), Gas Chromatography (GC) and Gas Chromatography-Mass Spectrometry (GCMS), the Rock-Eval method. GC and GC-MS methods allow to identify the hydrocarbons migrating from mature maternal rocks or deposits on specificity of their structure and distribution. TSF method states a semiquantitative estimation of the content of aromatic hydrocarbons typical for oils in the sediments. In the recent sediments perylene is the main component. In mature organic substance and in the oils the leading role is played by rather more low-molecular aromatic hydrocarbons. which The RockEval method gives the chance to diagnose allochtonous bitumoids in rocks by S1/Corg value. The method is used for studying unmature sea sediments for definition of type and sources of organic substance containing in them. In the sediments of the Khatanga Gulf were sampled 57 stations (77 samples). The surface deposits (up to 0,5 m) – sand, from 0,5 to 2 m – oozes. The content of methane changes from 0,001 to 7,4 cm3/kg, an average – 0,28 cm3/kg. The highest contents of methane are observed in oozy sediments with hydrotroilite. Sediments are enriched by nitrogen (an average of 295 sm3/kg), content of CO2 reaches up to 43 sm3/kg. Sediments of Khatanga Gulf are characterized by the low contents of CH4 in comparison with sediments of the Yenisei Gulf, the Black Sea and others. In sediments are noted existence of hydrotroilite, the plentiful contents the authigenic sulfides which are sulphate-reducing products. The significant amount of sulfate ions contains in interstitial water of sediments up to the depth of 2 m that promotes sulfate- reducing processes. It is known that in anaerobic conditions at intensive processes of the sulfate reduction methanogenesis by a complex of the methane-producing bacteria is slow down. Possibly, the low content of methane in pelitic oozes in Khatanga Gulf (at the level of "traces" - 17,4х10-3 cm3/kg and below) is explained by it. The content of methane homologues in sediments (cm3/kg n×10-3): light homologues - on the average 0,32 (a maximum - 1,25), heavy homologues – 0,31 (a maximum - 0,68). At several stations (11%) K value - (CnН2n+2/CnН2n) – 1.2÷3,7; anomalously high content of methane homologues is noted in the sediments. 12 samples of bottom sediments were analysed by the TSF method, the aromatic component of oil components is determined by fluorescence intensity and length of an exited wave and emission in them. Existence of oil-similar components in sediments is revealed in all samples, except the sediment from St. 9p where only perylene is fixed which is typical for the unmature sediments. The maximal intensity of a fluorescence from 1756 to 4109 units is noted in the sediments of stations 31, 14, 15, 2; 12; 14; 33; 20 where except perylene the sediments contain aromatic compounds, which is typical for "mature hydrocarbons", i.e. they include signs of migratory hydrocarbons presence (fig. 1). 142

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Figure 1 Fluorescence spectra (TSF) of extracts from sediments of Khatanga gulfs The molecular structure of n - and iso-alkanes is defined by a method of the gas chromatography (GC). By a character of an alkanes chromatogram and presence of low-molecular n- alkanes n-C15 – n-C23 it is possible to judge about impurity of thermogenous, deep hydrocarbons. According to gas-chromatographic researches of hexane extracts the most expressed signs of impurity of thermogenous hydrocarbons are fixed in sediments of stations 12, 14, 20. These signs are: the increased part relative to low-molecular n-alkanes (11,3÷23,3 %), significant increase in a share relative to low-molecular homologues (n-C15 - n-C20) as a part of n-alkanes, and the reduced coefficients of an oddness of n-alkanes in the range of n-C25-n-C31. Practically at all stations where anomalies of the HMH content in the sediments are recorded, the increased content of bitumoids (0,0025-0,005%), and in most cases anomalies of light (С2–С4) and heavy (C5-C6) homologues of methane are also revealed.

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Figure 2. The comparison of a seismic section and gravi-magnetic profiling to geochemical indicators in Khatanga Gulf

By the complex of geochemical indications 5 stations with microseepages of liquid hydrocarbon fluids (St. 12, 20, 33, 31, 2) and two stations with a seepage of hydrocarbon gases (St. 13, 38) are located in the gulf. Single micro seepages of liquid and gaseous hydrocarbon-fluids are dated for deep breaks, areas of the increased fracturing and porosity of sedimentary thickness (fig. 2). The received results testify to high informational content of a modern complex of methods of the HMH analysis in the bottom sediments at gas-geochemical survey of the water area. Under the influence of deep hydrocarbon flows in the gulf sediments authigenic mineral formation takes place. At areas with microseeps of liquid hydrocarbon fluids sulphidic mineralization (hydrotroilite, melnicovite, pyrite) takes place, on areas of gas seeps (methane, СО2) – calcium carbonate mineralization (carbonate crusts, calcite, gypsum).

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Figure 3. The scheme of zoning of the probability of oil-and-gas prospects of the Khatanga Gulf (according to geochemical data)

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A065 By results of geochemical researches the water area of the gulf was divided into zones of the highest, high and average probability of prospects of oil-and-gas content. Four areas with anomalously high indicators of the content of gas and fluid hydrocarbons are located in the gulf. Anomaly I is correlated with Sopochnaya group of rises, anomaly II – to Severo-Sibirskaya monocline, anomaly III – to Syundakskaya step (stage), IV – to Nordvikskaya group of rises and to local structure Novaya. The show of hydrocarbonic fluids at st. 31 and 33 are confined to the salt stock and Nordvikskaya group of rises. The show of hydrocarbonic fluids at st. 33 is confined to local structure Novaya, at st. 20 – to local structure Kosistaya (fig. 3). In Anabaro-Hatangsky oil and gas-bearing region according to geophysical data three zones of rises are delineated: Sopochnaya, Nordviksky and Kiryako-Tassky which are the most perspective for searches of deposits of hydrocarbons in the Khatanga Gulf. Now only one non-commercial oil deposit is available on Nordvikskaya shaft. The deposits are not found yet on the other shafts. The Sopochny group of rises is included in the Belogoro-Tigyansky shaft where there are small oil deposits (Kozhevnikovskoe and Yuzhno- Tigyanskoe [Deviatov, Savchenko, 2012]. Geochemical anomalies coincide with the perspective oil and-gas zones selected by the method of gravimetric detection and delineation of oil and gas reservoirs and with local areas of loosening in the sediment thickness, outlined by a gravity prospecting, and also they coincide with AVO- anomalies (fig. 2). The agreement of geochemical anomalies with the perspective zones outlined on the basis of geotechnical researches, increases probability of the forecast of oil-and-gas content of the studied area. Thus, the complex of geochemical researches including the studying of high-molecular hydrocarbons and hydrocarbonic gases, as well as geologic-geophysical researches, show high prospects of the oil and gas contents of the water area of Khatanga Gulf. REFERANCE Deviatov V.P., Savchenko V.I. (2012) New data to an overestimation of hydrocarbon resources AnabaroHatangsky petroleum region. Oil and gas geology (Russia) 1, 55-61.

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Identifying Environmental Impacts from Large-Scale Methane Releasing Events by Using Marine Geological Records: Offshore SW Taiwan and the Northern South China Sea Min-Te Chen National Taiwan Ocean University, [email protected] ABSTRACT Thermodegradation and biodegradation of sedimentary organic matter are proposed as two major sources of methane hydrate stored in sediments. Vertical methane fluxes released from the methane hydrates to the ocean and ultimately, the atmosphere, due to destabilizations of the geological setting of sediments may bring non-negligible environmental impacts that could be catastrophic on regional to global scale. In light of this important environmental and societal consequences while exploratory drilling of methane hydrate is under planning in offshore areas of SW Taiwan, we aims to develop isotope and organic biomarker proxies sensitive to past methane vertical pulses in marine cores from offshore areas of SW Taiwan. We investigated the linkage between the proxy indicative methane releasing events and regional climatic changes [sea surface temperature (SST), productivity, hydrology, etc.] in the geological archives. The primary outcome of this research is to identify any possible catastrophic impacts from past methane releasing events learning from the geological archives on decadal to millennial time scales. Methane of biogenic origin is characterized by very negative values on carbon isotopes, which provides easily distinguishable indicator for past methane releasing events. Planktic and benthic foraminifer shells were also picked up for oxygen isotope analysis plus planktic AMS 14C dating for establishing high precision chronologies of the cores. Organic δ13C of bulk sediments and extracted hydrocarbons were analyzed in this study too for comparing with inorganic δ13C for revealing the possible imprints left in sediment cores by methane releasing. Past SSTs were estimated by analyzing TEX86 from the same core to address any possible warming impacts caused by rapid outgassing of methane in the offshore areas of SW Taiwan. Our initial results on an analysis of a marine sediment core from the northern South China Sea (MD972146, water depth 1720m) show that the relatively lighter carbonate isotope events had been persistent features since the last glacial when the sea level was lowered by ~120m. The lighter carbon isotope events appear to be no significant linkage with warmer SST, or linking with some slightly warmer events. We need more high-resolution SST data to demonstrate clearly how the past methane releasing events had been linked with warmer sea surface conditions.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A073

Dynamic Behavior of Methane Gas Hydrates Formation and Decomposition with a Mid-Scale Apparatus So-Siou Shu and Ming-Jer Lee Department of Chemical Engineering, National Taiwan University of Science & Technology, Taiwan [email protected], [email protected]

ABSTRACT A mid-scale apparatus, operable at low temperatures and elevated pressures, was installed in this study to investigate the dynamic behavior during the processes of gas hydrates formation and decomposition. The dynamic experiments have been conducted for observation of methane hydrate formation at 275 K/42.8 bar and that of hydrate decomposition as pressure decreasing from 42.8 bar to 1.0 bar. The experimental data of temperature distribution, pressure, and methane flow rate varying with time provide useful evidences to get more insight into the mechanisms of methane hydrate formation at constant T/P and decomposition by depressurization. Also these results are helpful to the software development for natural gas hydrate production. INTRODUCTION Natural gas hydrate is a plenty of alternative energy source in ocean. Among several others, the depressurization method is one of potential ways to gas hydrate production (Ji et al., 2001). To develop the technologies of gas hydrate production and gas storage in hydrates, the dynamic behavior of gas hydrate formation and decomposition is fundamental important. A mid-scale apparatus equipped with a pair of visual windows was installed to observe the phase behavior in the high-pressure cell during the hydrate formation and decomposition. The signals of temperature reading at different positions, pressure reading, and total volume of methane gas consumption during the formation period and that of gas releasing during the depressurization period were recorded by a data acquisition system. These dynamic data are useful in modification of simulation package for evaluation of production of natural gas from gas hydrate reservoir. EXPERIMENTAL SECTION Fig. 1 is the schematic diagram of the mid-scale apparatus (about 1.6 liter of internal volume) for observation of dynamic behavior during the gas hydrate formation and decomposition. Fig. 2 is the design of the high-pressure cell (1) with the dimension of 100 mm (I.D.) x 200 mm (height). The cell is equipped with a pair of high-pressure glass windows (25 mm I.D.) and six RTD temperature sensors (4, T1 to T6) from bottom to top. These sensors are used for measuring temperature profile in the cell through the courses of gas hydrate formation and decomposition. A pressure transducer (3) is employed to measure the pressure in the cell. The cell is immersed in a thermostatic bath (6). In each experimental run, temperature of bath is maintained at a specific value. For each run, the cell was evacuated first. Then pure water is charged into the cell with a hand pump until the water level reaching around the middle of the window. Subsequently, methane was injected into the cell also using a syringe pump (2). The injection was continued until a specific pressure to be attained. As pressure higher than liquid-gas-hydrate three-phase coexistence pressure, methane hydrates started to form. 148

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A073 During the hydrate formation, the syringe pump was operated at a constant-pressure mode. Fresh methane can be introduced instantaneously into the cell by the syringe pump, to maintain constant pressure, as methane gas transfers gradually into hydrate phase. The total volume of make-up methane was monitored by a digital video camera through the entire course. As the rate of hydrate formation approaching to zero, the system was depressurized by opening the metering valve, which is connected to wet test meter (7) at atmospheric pressure. The temperature distribution, pressure, and total volume of released methane were also recorded by the data acquisition system (5) during the depressurization process. The images of phase states in the cell can also be taken through the windows anytime. P-10

To GC 8 E-14

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gas out P1

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Fig. 2: Design of the high-pressure cell RESULTS & DISCUSSION In the first experimental run, the bath temperature was maintained at 275 K and cell’s pressure at 42.8 bar, which is higher than the corresponding gas-liquid-hydrate three-phase coexistence pressure, about 33 bar (Servio and Englezos, 2002). Fig. 3 presents the temperature distribution and the rate of methane make-up (approximately the rate of hydrate formation) varying with time. Since the hydrate formation is an exothermic process, the temperature histograms can provide experimental evidences to reveal where are hydrates generated. According to the history of temperature readings, the hydrates formation is starting from the liquid level to the top of cell because temperature T4 increases dramatically from 275 K to 279 K within the first 20 min. Then temperature T5 subsequently increases up to about 277.2 K, which is attributive to the hydrates formation zone propagating from the liquid level to the top of cell. As also seen from Fig. 3, the hydrate formation rate reached to a maximum at about 135 min and the hydrate formation was ended at time around 200 min. 149

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Fig. 3: A plot of temperature profile and rate of make-up methane vs. time during gas hydrate formation Fig. 4 illustrates the variations of temperature distribution and total volume of methane released from the hydrates in the hydrates decomposition process induced by depressurization. In contrast to the hydrate formation, it is an endothermic process for hydrate decomposition. At the beginning of the depressurization process, the temperature at the top of the cell (T6) drops suddenly due to high pressure methane expansion. Temperatures T5 and T6 also decrease simultaneously which may be resulting from cooling effect via heat conduction. As seen from Fig. 4, we suggested that hydrates docomposition was starting from the top of cell since T5 dramatically drop down to 272 K after 10 min of depressurization. Temperatures T4 and T5 reduce to below 273 K within the first 50 min of decomposition process due to the endothermic effect. At the same time we found a lot of ice flakes fromed around the interface of the liquid and the vapor phsaes. The decomposition was ended at about 75 min.

Fig. 4: A plot of temperature profile and total volume of released methane vs. time during gas hydrate decomposition

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A073 CONCLUSIONS A mid-scale apparatus with an internal volume of 1.6 liter was installed in the present study for investigating the dynamic behavior of gas hydrate formation and decomposition processes. The phase behavior inside the cell can be visually inspected through the glass windows, while the records of temperatures, pressures, volumetric values at different time periods provide the experimental evidences to find the mechanism of methane hydrate formation and decomposition. The observations show that methane hydrate formation is starting from the interface between water and vapor phases and propagating to the top of cell (vapor phase, initially). In the second stage, bubble-like methane hydrates are then formed below the water level. Through the depressurization process, we found that methane hydrates decomposed from the top of cell at the initial step, and then propagating to the hydrates below the water level. The experimental results provide us valuable information to get more insight into the mechanisms of methane hydrate formation at constant T/P and decomposition via depressurization. Also these results are useful to the software development for natural gas hydrate production. REFERENCES Ji C., G. Ahmadi, and D. H. Smith (2001),”Natural Gas Production from Hydrate Decomposition by Depressurization,” Chemical Engineering Science, 56(20) 5801-5814. Servio, P. and P. J. Englezos (2002), “Measurement of Dissolved Methane in Water in Equilibrium with Its Hydrate,” Journal of Chemical & Engineering Data, 47 (1) 87-90.

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A New Force Field for Accurate Thermodynamic Properties of CH4THF Hydrates Jyun-Yi Wu and Shiang-Tai Lin* Department of Chemical Engineering, National Taiwan University, Taipei, 10617, Taiwan [email protected], [email protected]

ABSTRACT The accuracy of force field has a significant impact on the equilibrium and kinetic properties of a system determined from molecular dynamics (MD) simulations. In this work, we examined the performance of several existing force field parameters for simulating CH4-THF clathrate hydrates, and developed a new set of parameters that satisfies the following criteria: 1. reproducing the melting point of ice, 2. reproducing experimental solubility of THF and methane in water, respectively. 3. reproducing promotion effects of THF in CH4 hydrates. These criteria ensures that the thermodynamic properties can be reproduced in molecular simulation. While use of OPLS-AA for THF and CH4 and TIP4P-Ew for H2O reproduces the melting points of CH4-THF hydrates at various temperatures, the melting point of ice is too low and, as a consequence, the selfpreservation phenomena may be observed in the melting simulation. In addition, the solubility of CH4 in water is too high which may mis-lead the degree of mass transport driving force for the growth or melting of hydrates. In this work, we developed a new set of force field based on TIP4P-Ice of water, OPLS-AA for CH4 and a modified Girard parameters for THF. We show that this new set of parameters can reproduce the various thermodynamic properties of CH4-THF hydrates and is suitable for study their kinetic properties.

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Magmatic Water Contribution in Milos Submarine Hydrothermal Fluids: New Boron Isotopic Evidence Shein-Fu Wu Department of Earth Sciences, National Cheng-Kung University, also at Earth Dynamic System Research Center, NCKU, Taiwan Department of Geosciences, National Taiwan University, Taiwan [email protected]

Chen-Feng You and Yen-Po Lin Department of Earth Sciences, National Cheng-Kung University, also at Earth Dynamic System Research Center, NCKU, Taiwan [email protected], [email protected]

Eugenia Valsami-Jones School of Geography, Earth and Environmental Sciences, University of Birmingham, UK [email protected]

Emmanuel Baltatzis Department of Geology and Geoenvironment, National and Kapodistrian University of Athens, Greece [email protected]

ABSTRACT Magmatic water contributes significant amounts of volatiles to hot springs on land; however, its role is poorly understood in submarine hydrothermal systems worldwide. In this study, 41 new vent fluids collected from a shallow-water hydrothermal system, Milos in the Aegean Sea, were analyzed for B and δ11B as well as major and trace elements. These results were compiled with previous data from Vulcano island, Taupo volcano, and other seafloor hydrothermal vents and laboratory super-critical phase separation experiments to quantify the effects of phase separation, water/rock interaction, and the contribution of magmatic water. Two Cl-extreme solutions were identified in Milos, brine fluids (Cl ~ 2000 mM) and vapor-like phase (Cl ~ 60 mM), in addition to some seawater-like fluids with high Mg and H2S. These fluids were characterized by high B/Cl molar ratios (1–5) and extremely low δ11B (3.34–7.24‰), except for the seawater-like fluids (~22‰). The uniquely high B/Cl (~9) and low δ11B (< 5‰) in Milos fluids support a scenario of magmatic water (6.9 mM and –2.5‰) addition in a deep reservoir, similar to what is reported in Vulcano Island and Taupo Volcano, and cannot be solely explained by water/rock interaction. Furthermore, these new B/Cl and Cl data intercepted with the experimental trends under supercritical phase separation, highlighting the critical importance of B addition at depth or potential fractionation of B/Cl and Cl during the sub-critical degassing process. These seawater-like fluids were possibly derived from a shallow reservoir exempt from magmatic water contamination. Using a simple binary mixing model of the evolved seawater and the magmatic water, the latter was estimated to contribute 18 to 47% of B in Milos fluids. A compiled diagram of B, Cl, B/Cl, and δ11B in hydrothermal fluids showed small B/Cl and large 1/B variation under sub-critical phase separation relative to supercritical conditions. The magmatic water component, which causes high B/Cl and low δ11B, is critical for deciphering the evolutionary history of shallow submarine hydrothermal fluids at Milos. 153

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A072

Molecular Dynamics Simulation for Quantitative Description of Thermodynamic Properties of Methane Hydrates Hung-I Chao, Hsuan Lo and Shiang-Tai Lin* Computational Molecular Engineering Laboratory, Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan [email protected], [email protected], [email protected]* ABSTRACT Molecular dynamics simulation has been a useful tool to unveil the molecular level details of clathrate hydrates. However, there are always questions regarding how close the simulation results represent the real behaviors of gas hydrates. In this work, we examine three important thermodynamic properties, dissociation temperature, solubility, and heat of dissociation, of methane hydrates simulated based on the combination of Tip4p-Ice for water and OPLS-AA for methane. The dissociation temperature represents the thermal stability of methane hydrates under thermal stimulations. The solubility of methane in water is related to the mass transport driving force during growth and dissociation of methane hydrates. The heat of dissociate determines the relative energetic stability between the solid and molten states. Our results show that the molecular model can reproduce the experimental dissociation temperatures under different pressures within 5 K. The simulated solubility of methane in water agrees with experiment within experimental uncertainties. The heats of dissociation are found to be about 5% lower than experimental values. These results indicates that the molecular model can reproduce key thermodynamic properties of methane hydrates with quantitative accuracy.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A078

Production Analysis for Depressurized Methane Gas Recovery from Hydrate Reservoir in Offshore Southwestern Taiwan Yan-Yu Chen and David Shan-Hill Wong* Department of Chemical Engineering, National Tsing-Hua University, Taiwan [email protected], [email protected]

Ying-Chih Liao Department of Chemical Engineering, National Taiwan University, Taiwan [email protected]

ABSTRACT Offshore hydrate reservoir southwestern of Taiwan has been identified as a promising zone for natural gas recovery. Previous studies have shown that there is a wide occurrence of gas hydrates in the undersea sandstone layers in the water depth ranging from 500 to 3000 m. One of the efficient ways to recover natural gas from the hydrate reservoirs is directly reduce the pressure with drilling wells and collect the released methane gas, or the so-called depressurization method. In this study, a simple lumped material and energy balance model was developed to for estimating gas production rates with given reservoir characteristics, such as hydrate zone thickness, porosity, hydrate saturation, temperature, and pressure. A fast screening method was developed by integrating Monte Carlo approach with the lumped model to estimate the distribution of gas production rates given the distributions of reservoir characteristics for the possibilities for commercial operations. A more detailed 2D model simulation will then be used to validate operations and reservoirs that have best potential for commercial production. The total gas production, gas production rates, and extraction period will also be predicted to probe the possibility for commercial drilling. INTRODUCTION Natural gas hydrates are crystalline water-based solids physically resembling ice, and are stable in high pressure P and low temperature T. The undersea methane hydrate reservoirs have been estimated to probably contain 2–10 times more than the currently known conventional natural gas reserves [1-3]. Because of the rising demands of energy, natural gas hydrate recently attracts significant attentions worldwide and much research efforts have been spent on developing new technologies for feasible gas production from hydrate reservoirs [49]. One of the major methods for gas production from hydrate reservoirs [10] is depressurization method, which decreases reservoir pressure below the hydrate decomposition pressure. Although depressurization seems promising for gas hydrate production, more drill investigations are still needed to improve the gas collection efficiency for commercial operations.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A078 To improve recovering gas from hydrate reservoirs for saving the time and facility cost, computer simulations are regularly used prior to on-site drilling process. With those tools, well locations and detect drilling problems can be easily determined by engineering, so that both feasibility and profitability can be maximized. To skip detail calculations and to fast evaluate drilling costs, in this study, a quick evaluation was used to estimate the possibility of methane production from hydrate reservoirs in southern offshore Taiwan, and the key geological or physiochemical data that will affect the production was identified. A simple material balance model is developed by combining energy balance and multiphase flow in porous media to evaluate production rates from hydrate reservoirs in southwestern offshore Taiwan. A reservoir containing low water saturation can be more easily produced than high water saturation. For a high water saturation reserve, gas will not be easily recovered from the well until water saturation is lower than 0.7. High withdraw rate helps to reduce the period of water extraction and shorten the start time of recovering gas. However, operating cost may overwhelm the profit with large withdraw rate. The economical assessment is necessary for decision making to start drilling and will be cooperated with the material/energy balance model in the future to optimize the profit. Table 1 Gas hydrate resource assessment of KP-7. Parameters Category

Possible gas hydrate occurrence zones

Area (km2) (triangular

Gross thickness (m) (lognormal

N/G (lognormal

Porosity (lognormal

Sh (normal

distribution)

distribution)

distribution)

distribution)

distribution)

Min

Max

67.55

96.48 Med

P90

P10

P90

P10

P90

P10

mean

Std Dev.

195.39

309.27

0.1

0.4

0.39

0.5

0.25

0.066

82.02

Fig. 1: Variation of methane produce rates with time at different withdraw rates

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Fig. 2: Probability distribution of hydrate depletion time at various withdraw rates

Fig. 3: (A) Scatter plot and (B) histogram of top 25% and lowest 25% of methane produce rate with 50 kg/s at first year

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A078

Fig. 4: Total gas production with different rate withdraw and hydrate in place REFERENCES Haldar A, Mahadevan S (2000), Probability, reliability, and statistical methods in engineering design. New York ; Chichester England: John Wiley. Johnson EA, Wojtkiewicz SF, Bergman LA, Spencer BF (1997), "Observations with regard to massively parallel computation for Monte Carlo simulation of stochastic dynamical systems", International Journal of Non-Linear Mechanics, 32(4), 721-734. Kareem A, Hsieh CC, Tognarelli MA (1998), "Frequency-domain analysis of offshore platform in non-Gaussian seas", Journal of Engineering Mechanics-Asce, 124(6), 668-683. Kirkner DJ, Spencer BF, Kandarpa S (1996), "Monotonic loading of brittle materials: A stochastic damage model", In: Probabilistic Mechanics & Structural Reliability: Proceedings of the Seventh Specialty Conference. Edited by Frangopol DM, Grigoriu MD. New York: Amer Soc Civil Engineers; pp. 354-357. Kowalsky MB, Moridis GJ (2007), "Comparison of kinetic and equilibrium reaction models in simulating gas hydrate behavior in porous media", Energy Conversion and Management, 48(6), 1850-1863. Moridis GJ, Silpngarmlert S, Reagan MT, Collett T, Zhang K (2011), "Gas production from a cold, stratigraphically-bounded gas hydrate deposit at the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope: Implications of uncertainties", Marine and Petroleum Geology, 28(2), 517-534. Moridis GJ, Kim J, Reagan MT, Kim S-J (2013), "Feasibility of gas production from a gas hydrate accumulation at the UBGH2-6 site of the Ulleung basin in the Korean East Sea", Journal of Petroleum Science and Engineering, 108), 180-210. Kurihara M, Sato A, Ouchi H, Narita H, Masuda Y, Saeki T, et al. (2009), "Prediction of Gas Productivity From Eastern Nankai Trough Methane-Hydrate Reservoirs", Spe Reservoir Evaluation & Engineering, 12(3), 477-499. Konno Y, Oyama H, Nagao J, Masuda Y, Kurihara M (2010), "Numerical Analysis of the Dissociation Experiment of Naturally Occurring Gas Hydrate in Sediment Cores Obtained at the Eastern Nankai Trough, Japan", Energy & Fuels, 24), 6353-6358. Makogon IUF (1997), Hydrates of hydrocarbons. Tulsa, Okla.: PennWell Pub. Co. 158

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A080

Three-Dimensional Structural and Stratigraphic Architectures and Gas Hydrate Occurrences in a Fault Zone of the Accretionary Wedge Off SW Taiwan Ke-Shu Li and Andrew Tien-Shun Lin Department of Earth Sciences, National Central University, Taiwan [email protected], [email protected]

Char-Shine Liu Institute of Oceanography, National Taiwan University, Taiwan [email protected]

ABSTRACT The Yung-an ridge (YAR) is a high potential area for gas hydrate, where contains several reservoir types. A group of gas hydrate bearing sediments is identified in this text and its polarity is as same as sea floor that implies seismic ray into high speed zone. Area of this gas hydrate bearing sediments is 2.5 km2 at east slope of the YAR. There are four proposed drilling sites in the YAR area (two at of the YAR, one at paleochannel-sand and one at fault-related seeping zone). More detail data should be collected for deciding first priority of these proposed sites. INTRODUCTION The Philippine Sea plate colliding and overriding crust of the South China Sea resulted in an accretionary wedge off southern Taiwan where deformation front thrust is the western boundary (Teng, 1990; Liu, 1997) (Fig 1a). The area offshore Southwestern(SW) Taiwan is characterized by a narrow shelf (~10km; Yu et al., 2009) linking up with broad continental slope and high sedimentation rate (0.7~4.5 mm/year, Lin et al., 2014), where are good conditions for gas hydrate formation. Wide distributed BSRs (bottom simulating reflectors) in the continental slope offshore SW Taiwan had been identified in reported studies (Chi et al., 1998; Liu et al., 2006). BSR is the bottom of gas hydrate stability zone with free gas beneath. Low velocity zone of free gas results in BSR having opposite polarity compared to the reflector of sea floor. Water samples collected near sea floor in study area also contain high concentration of methane (>100,000nL/L, Chuang et al., 2006). The capacity of gas hydrate was estimated around 2.7 trillion cubic meters (Lin, 2011). Depending on many surveys, several candidate drilling sites (white circles in Fig. 1) for gas hydrate are identified but detail investigation are needed. The goals of this study (1) are more understanding regional structures and gas hydrate distribution and (2) construct 3D model with structural and stratigraphic architectures for future pilot drilling. SEISMIC DATA INTERPRETATION The seismic data collected in traditional 2D method is processed and resampled to psudo-3D seismic data volume by seismic exploration lab, NTU. The YAR had been classified to R5.1 (Lin et al., 2008) 159

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A080

Fig. 1: (a) Topographic and tectonic features off SW Taiwan (coordination system: UTM 50N). Rectangle at center represents study area. White circles are proposed drilling sites for gas hydrate. (b) Geometry of psudo3D seismic data. Contours represent depth picked from seismic data. which represents a homoclinal ridge. The profiles IL83, IL63, IL49, IL33 and IL18 are presented from north to south and the lower four profiles transit the proposed sites (Fig. 2). The slope basin at east of the YAR has good conditions for methane gas forming including sources, depth and temperature. Free methane gas will migrate to the ridge because of buoyancy, then may be trapped in porous layer (IL63) or seeps to sea floor through cracks (IL33). In these conditions with enough fluids, free gas will transform to gas hydrate with positive polarity of reflector as sea floor. The layers in the slope basin at west of the YAR, dip to east, was eroded by branch of the Penghu canyon system from where free gas escaped. Thus it results in lower intensity of BSR in west slope basin compared to that in east one. But a paleo channel with porous sand above BSR is identified and characterizes as same polarity as sea floor (IL49), implies presence of gas hydrate. Eastern fault of the eastern slope basin has characteristics of strike-slip fault and causes layers uplifted with saddle-like shape in NS direction (Fig. 3). The unconformity with a porous layer, may charge free methane gas at saddle point and was uplifted near sea floor at south, is a proposed site in IL18. A group of gas hydrate bearing sediments like IL 83 at east of YAR, with positive polarity as sea floor is identified in this text, is 2.5 km 2 in wide and the thickest part could reach 66ms (50~60m). Therefore, potential resource of this reservoir is considerable. The slope stability has to be considered for future drilling resulted from several huge MTDs (Massive transport deposits) discovered in seismic data. Modernly, distributions of MTDs seem to be toward north and shallower depth. CONCLUSIONS 1. A group of gas hydrate bearing sediments at eastern portion of the YAR is picked in this text. Its potential resource is considerable. 2. Methane gas generated in slope basin migrates to the ridge where strong reflections above BSR forms. It implies gas hydrate presenting at IL33 and IL63. 160

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A080 3. A pack of paleochannel-sand above BSR is picked at west of the YAR, which has positive polarity implied highly potential of gas hydrate (IL49). 4. The boundary fault of eastern slope basin is a seeping path for free gas. It will transfer to gas hydrate when free gas migrates upward (IL18). 5. These proposed drilling sites need more data to evaluate priorities.

Fig. 2: Inline oriented profiles with two way travel time in vertical axis. The enlargement figures next profiles are targets of gas hydrate drilling. The dashed line at IL83 is top of gas hydrate bearing sediments. The dotted lines at eastern portion of slope basin indicate the strike slip fault. The icons of wells are positions of proposed drilling sites. Triangles indicate BSR surface. 161

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A080

Fig.3: 3D morphology of unconformity and gas hydrate bearing sediments. Contours indicate depth in two way travel time. White sticks represent the boundary fault surface. REFERENCES Chi, W. C., Reed, D. L., Liu, C. -S., & Lundberg, N. (1998), “Distribution of the bottom simulating reflector in the offshore Taiwan collision zone,” Terrestrial Atmospheric Ocean Sciences, 9(4), 779–794. Chuang, P., Yang, T. F., Lin, S., Lee, H. F., Lan, T. F., Hong, W. L., Liu, C. S., Chen, J. C. & Wang, Y. (2006), “Extremely high methane concentration in bottom water and cored sediments from offshore southwestern Taiwan,” Terrestrial Atmospheric and Oceanic Sciences, 17(4), 903-920. Ecker, C., Dvorkin, J., & Nur, A. M., (2000), “Estimating the amount of gas hydrate and free gas from marine seismic data,” Geophysics, 65(2), 565-573. Lin, A. T., Liu, C. S., Lin, C. C., Schnurle, P., Chen, G. Y., Liao, W. Z., Teng, L. S., Chuang, H. J. & Wu, M. S. (2008), “Tectonic features associated with the overriding of an accretionary wedge on top of a rifted continental margin: an example from Taiwan,” Marine Geology, 255(3), 186-203. Lin, C. C. (2011), “Geological controls of gas hydrate occurrences and gas hydrate resource assessment, offshore southwest Taiwan,” (Doctoral dissertation. Institute of Geophysics, National Central University, (Report in English)). Lin, C. C., Lin, A. T. S., Liu, C. S., Horng, C. S., Chen, G. Y., & Wang, Y. (2014), “Canyon-infilling and gas hydrate occurrences in the frontal fold of the offshore accretionary wedge off southern Taiwan,” Marine Geophysical Research, 35(1), 21-35. Liu, C. S., Huang, I. L. & Teng, L. S. (1997), “Structural features off southwestern Taiwan,” Marine Geology, 137(3), 305-319. Liu, C.S., Schnurle, P., Wang, Y., Chung, S.H., Chen, S.C., Hsiuan, T.H. (2006), “Distribution and characters of gas hydrate offshore southwestern Taiwan,” Terrestrial, Atmospheric and Oceanic Sciences, 17(4), 615-644. Teng, L. S. (1990), “Geotectonic evolution of late Cenozoic arc-continent collision in Taiwan,” Tectonophysics, 183(1), 57-76. Yu, H. S., Chiang, C. S., & Shen, S. M. (2009), “Tectonically active sediment dispersal system in SW Taiwan margin with emphasis on the Gaoping (Kaoping) Submarine Canyon,” Journal of Marine Systems, 76(4), 369-382. 162

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A084

Gas Composition of the Venting Bubbles from the Formosa Ridge in the Gas Hydrate Potential Area, Offshore of SW Taiwan Tsanyao Frank Yang Department of Geosciences, National Taiwan University, Taiwan [email protected]

Tomohiro Toki Department of Chemistry, Biology, and Marine Science, University of the Ryukyus, Japan

Saulwood Lin Institute of Oceanography, National Taiwan University, Taiwan

Hideaki Machiyama Kochi Inst. Core Sample Res., JAMSTEC, Japan

ABSTRACT Bottom Simulating Reflections (BSRs) are widely distributed in offshore of southwestern Taiwan which infers the existence of potential gas hydrates underneath the seafloor sediments. Many mud volcanoes and mud diapirs, which

are considered to be genetically related to the dissociation of gas hydrates, are present in offshore and on land southwestern Taiwan. In order to examine the formation process of mud volcanoes and diapirs in offshore southwestern Taiwan, we conducted the diving surveys around the selected sites, using ROV Hyper-Dolphin and R/V Natsushima of JAMSTEC (NT07-05 Cruise) in March, 2007. Dense chemosynthetic communities were discovered by direct observation using ROV at water depth of 1120-1140 m on the top of the Formosa Ridge, where is located in the passive margin of northern South China Sea. Gas bubbles and hydrates were found within the colony. Subsequently, the bubbles became hydrates and accumulated within the sampling chamber and tube of WHATS sampling system. It is the first time to observe the hydrates in-situ at the sea floor surface in this region. The gas samples were transferred to the Giggenbach bottles with alkaline solution and the low permeability evacuated bottles for further gas and isotopic analysis in on-shore laboratory. The dry gas composition was dominated with CH4 (90-94%), however, CO2 and CO were not detected in the samples. The CH4/C2H6 ratios range from 7600 to 15000, and the 13C and D data of CH4 gases are -68.9 ~ -71.3o/oo and -205 ~ -208o/oo, respectively. It indicates a bacteria origin with carbonate reduction source for those gas samples. Low 3He/4He isotopic composition (0.34Ra) is consistent with the crustal source for the mud volcanoes in this region. The existence of H2S (197-289 ppm) in the samples can explain the dense occurrence of white crabs, Shinkaia crosnieri, which usually survive in the hydrothermal vent field.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A058

Methane Flux in the Northern South China Sea Chuang -Yi Ho and Chin-Chang Hung Department of Oceanography, National Sun Yat-sen University, Kaohsiung, 80424 Taiwan [email protected], [email protected] ABSTRACT Numerous submarine active mud volcanoes have been recognized in offshore southwest Taiwan. Recent studies have showed that the anomalously high methane concentrations in both bottom waters and core sediments above venting sites and high methane fluxes emission via those mud volcanoes in this area. However, methane fluxes estimated from water column to atmosphere showed large variation (0.1-82.3 μmol m-2 d-1 reported by Huang (2013) and 2.4-7.49 μmol m-2 d-1 reported by Chang (2010)) in the northern South China Sea (NSCS). In order to further estimate methane flux in the NSCS, we measured methane concentrations in the water column and estimated methane fluxed across the ocean to air in the mud volcano sites in 2013. The results showed that methane concentrations in the water column increased with increasing depth, and the highest concentrations occurred near the seafloor (about 40 nM). The estimated methane fluxes in the NSCS with mud volcanoes are approximately 4.7~25.9 μmol m-2 d-1 which are comparable with previous reported data. Nevertheless, methane samples could not be guaranteed to come from mud volcanoes or seeps because we did not see any sampling image during sampling process. To accurately estimate methane fluxes from sediment to bottom water, we will use ABL (Autonomous Benthic Lander) to collect methane samples in the summer 2014. Concentrations of methane via ABL sampling and methane fluxes will be presented in the meeting.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A050

Polygonal Fault System and Mud Mobilization in Cenozoic Chalky Limestone of the Chatham Rise, New Zealand Sudipta Sarkar, Joerg Bialas, Stephanie Koch, Cord Papenberg, Thomas Eckardt, Felix Gross, Jasper Hoffmann, Ingo Klaucke and Christian Berndt GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany Bryan Davy and Karsten Kroeger GNS Science, 1 Fairway Drive, PO Box 30368, Lower Hutt 5010, New Zealand Ingo Pecher and Kate Waghorn School of Environment, University of Auckland, Private Bag 92019, Auckland, New Zealand and SO226 Scientific Party ABSTRACT The findings of large (10 km diameter) elliptical seabed depressions [Davy et al., 2010] along the Southern margin of the Chatham Rise (600 m – 1100 m water depth) led to the acquisition of new 2D multichannel seismic reflection data and high resolution 3D P-Cable seismic data to gain more insight into a possible fluid migration system. A compilation of regional seismic data from various origins allowed to correlate DSDP site 594 results into the interpretation of the new data set. The stratigraphy is represented by the post-rift Cenozoic sedimentary sequence comprising of a lower marine mudstone overlain by chalky limestone and mudstone sequence. We find evidences for widespread polygonal faulting which is confined to a chalky limestone unit. Polygonal faults are randomly oriented on plan view with variable dip directions. The faulted unit is underlain by a unit showing transparent seismic facies with an irregular base and undulating top (Figure 1). We attribute the origin of this unit as a consequence of fluidization caused by overburden from sediment loading. In deeper water, a conical seismic feature with internal chaotic reflection is seen (Figure 2). The overlying strata show bending around the conical feature. A prominent radial fracture system is seen on top of the conical system. This feature is buried under a prominent late Miocene Unconformity and overlying sediment drift system. We attribute the origin of the conical feature to mud mobilization and rise. We do not find any evidence for present day release of fluid to the seabed.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A050 FIGURES

Figure 1: Polygonal faults are seen overlying a contorted and transparent seismic unit identified as fluidized strata. A prominent erosional unconformity is seen at 1.45 s twt.

Figure 2: A conical feature and overlying stratal bending. A radial fault system is developed at the crest of the conical feature. REFERENCE Davy B, Pecher I, Wood R, Carter L, Gohl K 2010. Gas escape features off NewZealand: Evidence of massive release

of

methane

from

hydrates,

Geophysical

doi:10.1029/2010GL045184

166

Research

Letters

37:

L21309,

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A086

Autonomous Detection, Mapping and Sampling of Marine Gas Seeps Using an AUV Stefan Wenau, Zsuzsanna Tóth, Volkhard Spiess, Hanno Keil, Jan-Hendrik Körber Department of Geosciences, University of Bremen [email protected], [email protected], [email protected], [email protected], [email protected]

Tai Fei Hella KGaA, Lippstadt

Dieter Kraus Institute for Watersound, Sonar Technology and Signal Theory, Hochschule Bremen [email protected] ABSTRACT A new autonomous underwater vehicle (AUV) for the detection, mapping, and sampling of marine gas emissions is developed by the company ATLAS Hydrographic and the MARUM/ University of Bremen. Marine gas emissions are of great interest due to their potential impact on atmospheric greenhouse gas concentrations and the interaction between global warming and increasing emissions in high latitudes. In the offshore hydrocarbon industry, gas emissions due to leaky pipelines, wellheads or CO2 sequestration sites, require permanent surveillance and monitoring. At present the detection and monitoring of gas emissions relies largely on ship-based hydroacoustic surveys. Single- or multibeam echosounders are used to image gas bubbles in the water column, which represent strong acoustic signals and produce distinct backscatter patterns. The analysis of these data requires online observation or manual post-processing in order to determine the spatial locations of gas emissions. Subsequent sampling of free gas is only possible during costly and time demanding remotely operated vehicle (ROV) operations. The main payloads of the new IMGAM AUV are an oblique-forward looking multibeam, multifrequency echosounder (MBES), a forward-looking imaging sonar, and the gas sampler. The detection of gas emissions shall be accomplished by on the fly, near real-time processing of the MBES data. As the simultaneous acquisition of bathymetry and water column data is expected to generate data volumes of up to 50 MB/s, high-performance detection algorithms are required. Eventually, the detector shall generate a three-dimensional environment in a relative coordinate system in which gas emissions are mapped as points (xyz). Crucial for the detection of gas bubble streams is the understanding of the effect of sensor geometry and acoustic attributes on the recorded acoustic data. Matlab routines were used to model gas bubble streams escaping from the seafloor. Different configurations of multibeam sensor inclination, frequency and signal characteristics were investigated for their effect on gas bubble stream detection. Sensor inclination and signal characteristics showed a large impact on the ability of the system to detect rising gas bubbles. Especially the detection of low activity seepage sites poses challenges for real time detection. We present a sequence of modelled bubble stream detections at varying sensor inclinations to illustrate differences in flare appearance in acoustic data due to sensor characteristics. Such variability in the detection of bubble streams may also affect the comparability of ship-borne flare detection and other methods such as seafloor observatories with mounted scanning or multibeam sonars. 167

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A042

Spatial Distribution and Turnover of Methane in the Chukchi Sea Matveeva Tatiana, Logvina Elizaveta, Semenova Anastasiya I.S.Gramberg All-Russian Research Institute for Geology and Mineral Resources of the Ocean (I.S.Gramberg VNIIOkeangeologia), St. Petersburg, Russia [email protected]

Alexander Savvichev Winogradsky Institute for Microbiology, Russian Academy of Science, Moskow, Rusiia [email protected] ABSTRACT We present here the data obtained during 2004, 2009 and 2012 cruises of Russian R/V “Professor Khromov”in the Chukchi Sea in the frame of RUSsian-American Long-term Census of the Arctic (RUSALCA) Project. Three sites were selected for the geochemical and geophysical investigations aimed for methane turnover study. The first Site is the pockmarks area discovered by USCGC during 2003 HEALY-0302 cruise in a shallow region of the Chukchi Cap at approximately 76° 30’N and 163° 50’W at the water depths of 565-680 м. The second is an extension of the Herald Canyon, and the third area is the South Chukchi Basin. During the cruises side-scan sonar (SSS) and sub bottom profiler (SBP) survey were carried out along two track lines in Herald Canyon (over 100 km long) and four track lines in the pockmark field (over 50 km long) using “SONIC3M” hydroacoustic system (side scan sonar and profiler © VNIIOkeangeologia). Coring aimed on geochemical characterization of sediment gas and pore water was carried out based on the geophysical data. This study provided a thorough assessment of spatial variation in CH4 concentrations in sediments within the studied areas of the Chukchi Sea. Site 1 – pockmarks. Two from three studied pockmarks characterize by indications of upward water infiltration and methane in sediments by headspace data. Character of composition and distribution of HC biomarkers in sediment testify a mix origin and considerable post-diagenetic level of the OM maturity. Site 2 - an extension of the Herald Canyon. Sediment cored within the Site is characterizing by increased methane content in sediment accompanying with decreasing trends of Corg suggesting in situ methane generation. Large-scale distribution of acoustic anomalies both on SSS and SBP records due to gas presence in sediment were traced in the central and southern parts of the studied area. Site 3 - South Chukchi Basin. The data obtained testify intensive processes of OM degradation, in situ methane generation and AOM. An isotope evidences on microbial origin of the methane in the South Chukchi Basin were obtained for first time (δ13C(CH4) varies from 92,8‰ to -96,7 ‰). Microbial study of water and sediments in respect to methane circle has shown high concentrations of biogenic elements and high rates of microbial processes in the upper sediment layers suggesting specific type of trophic chain in the Chukchi Sea.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A068

Evidence of Current Gas Hydrate Formation in the Near-Surface Sediments of Lake Baikal Tatiana V. Pogodaeva & Tamara I. Zemskaya Limnological Institute, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia [email protected], [email protected] ABSTRACT According to different sources, gas hydrate accumulations in natural occurrences, depending on the formation mechanism and the conditions of their location, are both of contemporary age and tens of thousands or millions years old. Our studies of near-surface gas hydrate accumulations in Lake Baikal areas with mud volcanoes and seeps mainly (25 gravity cores of 6 sites) showed increased (by 30-50%) mineralization of pore waters adjacent to hydrate sediments. The concentrations were high in the 5-cm sediment layer and varied in different ions (HCO3-, Cl-, NO3-, SO42-, Na+, K+, Ca2+, Mg2+, Fe2+). This phenomenon occurs when water molecules migrate from the sediments to the front of the hydrate formation. The calculated time for equalization of concentrations in the adjacent pore waters to medium core values of all ions is 30-130 days. This time is unlikely to exceed the time of formation of these hydrates. Formation of near-surface gas hydrate accumulations depends on the upward inflow of gas-saturated fluid and its intensity. The location of the flares and their intensity is known to periodically vary, which creates dynamic conditions for formation/decomposition of gas hydrates in the near-surface sediments. Thus, hydrochemical data analysis will probably allow a proper assessment of the age of gas hydrate accumulations considering the formation of the accumulations observed in Lake Baikal to be current and rather fast. ACKNOWLEDGEMENTS This work was supported by the SB RAS integration project No.82 and the Program of the RAS Presidium No.23.8.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A041

CAGE - Centre for Arctic Gas Hydrate, Environment and Climate Jürgen Mienert1, Karin Andreassen1, Jochen Knies1,2, JoLynn Carroll1,3, Stefan Buenz1, Bénédicte Ferré1, Tine Rasmussen1, Giuliana Panieri1, Catherine Lund Myhre1,4 1

CAGE, UiT - The Arctic University of Norway, Department of Geology, Dramsveien 201, N-9037 Tromsø, Norway; 2Geological Survey of Norway; 3Akvaplan-niva, Norway; 4NILU- Norwegian Institute for Air Research; Dept. Atmospheric and Climate Research [email protected]

ABSTRACT Research in the Centre of excellence CAGE focuses on the role of the Arctic Ocean methane hydrates in the context of environmental and climate issues. Warming of ocean temperatures is expected to reduce the stability of gas hydrates in continental margins, which may destabilize sediments and cause slope instabilities. Further, vast amount of methane that emanates from gas hydrates can have a significant impact on ocean chemistry and global warming if it reaches the atmosphere. By understanding the variability of methane release on time scales from hours to years and its dependence on oceanographic changes, we can quantify local and regional methane leakages. To achieve this we will deploy long-term observatories along the western Svalbard margin. Oceanographic measurements from the seabed, the water column and the air, along with modeling analysis, will provide the link between potential sources of elevated methane concentrations and the reason for variations. Details on the CAGE research plan and organization can be found on www.cage.uit.no to foster opportunities for cross-disciplinary collaboration. Based in Tromsø, at the world’s northernmost University, CAGE establishes the intellectual and infrastructure resources for studying the amount of methane hydrate and magnitude of methane release in Arctic Ocean environments on time scales from the Neogene to the present. The Centre of Excellence is funded by the Norwegian Research Council (grant No. 223259) over a period of ten years.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A059

Estimation of CH4 Release Over a Seep Area Offshore Svalbard Based on an Inverse Hydroacoustic Method Mario Veloso and Marc De Batist Ghent University, Vakgroep Geologie en Bodemkunde, Renard Centre of Marine Geology,Krijgslaan 281 s.8, 9000 Ghent, Belgium [email protected], [email protected]

Jens Greinert GEOMAR Helmholtz Centre For Ocean Research Kiel, Wischhofstrasse 1-3, 24148 Kiel, Germany [email protected]

Jurgen Mienert CAGE - Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geology at UiT-Norways Arctic University, Dramsveien 201, N-9037 Tromsø, Norway [email protected] ABSTRACT A seep site area at west of Prins Karl Forland (Svalbard) has been monitored since 2009 using hydroacoustic and video camera systems. Data has been analyzed to understand the dynamics of the gas release and used to quantify the gas flux released from the seabed. Hydroacoustic evidence shows that gas release is located at water depths between 200 and 400 meters and shows that some of the acoustic flares reach the sea surface. Accurate hydroacoustic information of the spatial distribution of the backscattering produced by bubble release could be acquired using an EK60 split-beam echosounder. Spot positions of the gas release were obtained applying a geometrical average over the backscattering produced by bubble release just above the seabed. A further developed version of the inverse hydroacoustic method introduced by Muyakshin and Sauter (2010) has been used to estimate the methane flux over the study area. This method assumes that the scattered acoustic energy is generated by the constructive interference of individual spherical bubbles. The method uses as input the backscattering volume strength (SV) of the bubble release above the seafloor, bubble size distribution (BSD) obtained from underwater video footage and bubble rising speed (BRS) values determined by models developed by different researchers (e.g., Leifer and Patro, 2002, Woolf 1993, Mendelson 1967). Flux calculations have been carried out over a selected area at ~220 m water depth using different BRS models and merged hydroacoustic data from 2009 and 2012. Our calculations use the Thuraisingham (1997) model of scattering produced by a single spherical bubble giving values between 179 and 285 T/yr of methane assuming continuous discharge and a bubble containing 100% of CH4. Temporal variability of methane fluxes between 2009 and 2012 was evaluated using the ‘common’ insonified area (27755 m2) with acoustic information of gas release showing that fluxes in 2009 have been higher by about a 27%. This variability highlights the need for repeated monitoring ideally in a higher temporal resolution than presented here (e.g. monthly). Because our study area seems to represent the reality of methane release in the Arctic, we believe that a continuous monitoring could reveal the possible implications of this release over the climate change. 171

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A075

Methane Hydrate Stability and Saturation in Ulleung Basin: A Numerical Model Perspective Wei-Li Hong and Marta Torres College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, USA [email protected], [email protected] Malgorzata Peszynska Department of mathematics, Oregon State University, USA [email protected]

Ji-Hoon Kim Petroleum and Marine Research Division, Korea Institute of Geosciences and Mineral Resources, South Korea [email protected] ABSTRACT The evolution of methane hydrate stability field in marine sediments, as well as the factors controlling gas transport and hydrate formation are the focus of active research. One particularly interesting issue is the formation of the near-seafloor massive hydrate deposits (MHD), which require migration of gaseous methane. The mechanisms that allow for gaseous methane migration to and through the gas hydrate stability zone remain unresolved. A recent drilling expedition to the Ulleung Basin, South Korea, provides a unique data set that specifically targets sites where acoustic data imaged chimneys characteristic of gas migration. MHDs here were observed as shallow as ~7 mbsf (meters below seafloor) at three sites. Positive Cl anomalies, as high as 1440 mM, suggest very rapid formation of MHD. To accurately simulate the evolution of such near-seafloor MHD, a well-behaved numerical model (Peszyǹska et al., 2010) and proper expressions of methane hydrate stability and saturation, especially under high salinity condition, are fundamentally important. To obtain proper expressions of methane hydrate stability and saturation, we first reviewed the available laboratory data from the literature. We then compared those data with prediction from various popular predictive models. Whereas at seawater values these models and data are very consistent, at salinity higher than seawater we observed significant inconsistencies among the various theoretical predictions, which point to potential issues that may arise when these theoretical predictions are applied. The best fit to laboratory data was achieved with the CSMGem (Sloan and Koh, 2007). We then incorporated the hydrate stability and saturation prediction of CSMGem into our numerical model to simulate the dilution-corrected pore water Cl profiles from Ulleung Basin and confirm the significance of advective migration of gaseous methane below the methane hydrate stability zone. REFERENCES Peszynska, M., M. Torres, A. Trehu (2010) “Adaptive modeling of methane hydrates” International Conference on Computational Science, ICCS 2010 Procedia Computer Science, 1, 709-717. Sloan Jr, E. D. and C. Koh (2007). Clathrate hydrates of natural gases, CRC press.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A031

Modeled Evolution of Subsea Permafrost Associated with Extensive Gas Escape Offshore the West Yamal shelf Alexey Portnov1,2, Jürgen Mienert1, Pavel Serov2 1

CAGE - Centre of Excellence for Arctic Gas Hydrate, Environment and Climate, UiT The Arctic University of Norway, Tromsø, Norway 2 I.S. Gramberg VNIIOkeangeologia, Saint-Petersburg, Russia

ABSTRACT Thawing subsea permafrost controls methane release bearing a considerable impact on the climate-sensitive Arctic environment. Significant expulsion of methane into shallow Russian shelf areas may continue to rise into the atmosphere on the Arctic shelves in response to intense degradation of relict subsea permafrost. The release of formerly trapped gas, essentially methane, is linked to the permafrost evolution. Modeling of the permafrost at the West Yamal shelf allowed describing its evolution from the Late Pleistocene to Holocene. During the previous work we detected extensive emissions of free gas into the water column at the boundary between today’s shallow water permafrost and deeper water non-permafrost areas. We integrate modeling results of relict permafrost distributions with these field data from the South Kara Sea. Modeling results suggest a highlydynamic permafrost system that directly responds to even minor variations of lower and upper boundary conditions, e.g. heat flux from below and/or bottom water temperature changes from above. We present several scenarios of permafrost evolution and show that potentially minimal modern extent of the permafrost at the West Yamal shelf is limited by ~17 m isobaths, whereas maximal probable extent coincides with ~100 m isobaths. The model also predicts seaward tapering of relict permafrost with its maximal thickness 275-390 m near the shore line. The model adapts well to corresponding field data, providing crucial information about the modern permafrost conditions, current location of the upper and lower permafrost boundaries and its possible impact on both the hydrosphere and atmosphere in a warming Arctic.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Poster Session III: September 4th (10:50-11:20)-GIMS12A036

Methane as a Potential Driving Force to Form the Pingo-Like Geatures at the South Kara Sea shelf Pavel Serov and Alexey Portnov CAGE – Centre of Excellence for Gas Hydrate, Environment and Climate, Tromso, Norway; I.S.Gramberg VNIIOkeangeologia, Saint-Petersburg, Russia [email protected], [email protected]

Jurgen Mienert CAGE – Centre of Excellence for Gas Hydrate, Environment and Climate, Tromso, Norway [email protected]

Petr Semenov I.S.Gramberg VNIIOkeangeologia, Saint-Petersburg, Russia [email protected]

ABSTRACT During the cold stages of the Pleistocene a 275-390 m thick layer of permafrost was formed in subaerial conditions on the South Kara Sea shelf. At the end of the last ice age (~19 ka) an extensive transgression of the shelf areas provoked active thawing of relic subsea permafrost and significant methane release. Research of gas seeps in the South Kara Sea shelf west of Yamal peninsula focused on pingo-like features (PLFs) because they may directly connect to overpressured accumulations of methane released from melting permafrost. We used high-resolution seismic (HRS) data to describe PLFs for further gravity coring at PLF flanks, crests and surrounding areas. HRS data show 4 distinct circular mounds towering ~5-9 m above the seafloor relief within two sites at the West Yamal Shelf. In the seismic image the mounds present acoustically transparent dome areas bounded by sections of normal sedimentary reflections dipping towards the flanks. Sediment cores taken from two PLFs reveal elevated methane concentrations (up to ~120000 ppm) at PLF 2 while PLF 1 has methane concentrations lower than the background level. Hydrocarbon gases analysis suggest a microbial signature expressed in low wet gas fraction, δ13CCH4 values ranging from -55,1‰ to -88,0‰ and and δDCH4 values varied from -175‰ to -246‰. Studies of n-alkanes and isoprenoids do not indicate the presence of thermogenic hydrocarbons that escaped from deep hydrocarbon sources. Thus, there appears to be an absence of fluid discharge from the oil and gas deposits at the South Kara Sea shelf. Low content of total organic carbon restricts extensive methane generation in the very upper part of anoxic sediments thus indicating high methane concentrations at PLF 2 as a result of migration of microbial gas. We integrate the results of geochemical studies and seismic data with models of permafrost evolution. According to the modeling results, permafrost at the South Kara Sea shelf changes quite rapidly in relation to the sea level rise and ocean temperature fluctuations. Even minor changes of the boundary conditions can trigger melting of permafrost and methane release. We suggest a scenario of PLFs formation offshore as a direct consequence of extrusion of frozen sediments by overpressured methane accumulations in permafrost. After the formation of PLF frozen sediments became more subjected to impact of bottom water temperature and permafrost started to thaw. We hypothesize that PLF 2 is an older structure than PLF 1. PLF 2 has reached a degree of destruction that allows methane to migrate towards the seafloor. We suggest that PLFs may act as gas seepage hot spots in the Arctic. 174

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session X: September 4th (13:30-13:50)

Review of the Remote Hydroacoustic Methods for the Quantification of Gas Discharge from Underwater Bubble Seeps Sergey Muyakshin University of Nizhny Novgorod, 603950, Gagarin st. 23, Nizhny Novgorod, Russia [email protected] ABSTRACT The remote hydroacoustic methods based on the processing of the echo signals scattered by the ascending gas bubbles are now the main technique used for the estimation of the gas flux from natural underwater gas seeps. The goal of the presented paper is to show different approaches used for flux quantification in cases of random distributed bubble release in shallow lakes or reservoirs and localized bubble jets typical for the ocean margins and deep lakes. Different types of the sonar including single-, split- and dualbeam devices as well as multibeam echosounder and corresponding processing procedures are described briefly. The accuracy of different approaches is analyzed. The consideration is based on author’s experience, original publications and on investigations published by other researcher. INTRODUCTION Modern echosounder of different types are now very popular instruments for the remote estimation of the gas flux transported by bubbles ascending from the see bottom. Different research teams use somewhat variable approaches. We analyze these approaches from a unified point of view. Our main objective will be to reduce measurements errors. DIFFERENT TYPES OF BUBBLE RELEASE AND CORRESPONDING METHODS OF THE FLUX CALCULATION Bubble counting is applicable if individual bubbles are resolved in space and time (represented on the echogram with separated trajectories). It is typically for shallow lakes and reservoirs with soft gas bearing sediments on the bottom. Eq.(1) enables the calculation of the mass flux per unit area q. q=Vb(r0)P(h)Nb/(RTSt)

(1)

Here: Vb(r) =4/3∙π∙r3 – volume of the bubble with equivalent radius r, P(h)=Pa+ρgh – pressure at the depth h, Pa – atmospheric pressure, ρ – water density, g – free fall acceleration, Nb – number of detected bubbles, S – investigated area, t – duration of the measurement, T – absolute temperature, R – gas const. S=L∙h∙2∙tg(α*) where L – length of the ship trace, α* - half width of the directivity pattern. Bubble radius r or volume Vb(r) may be estimated directly through backscattering, which is possible by using split- or dual-beam sonar. Bubble radius r may be also estimated using inverse function r=r(Urise). The speed of the ascending bubble may be determined using slope of the bubble trajectories on the echogram. 175

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session X: September 4th (13:30-13:50)

The Eq.(1) (or similar one) was used, for example, in (Ostrovsky, 2008 and Didenkulov, 2011) for the flux calculation in lake Kinneret and reservoirs of Gorky power plant respectively. Eq.(1) is valid in the case of narrow bubble size distribution. It is typically for the bubble release from the soft sediments, where the size of the released bubble is controlled by buoyancy and surface tension of the sediments film (Ostrovsky, 2008). In the margin seas of the World Ocean, in the Black and Mediterranean seas, the lake Baikal gas bubbles escape the bottom in the form of local jets with high concentration of bubbles. For example, at the typical flux 73 tons/year and the average ascent rate 26 cm/s the jet with height of 2 and a diameter of 0.2 m contains about 3600 bubbles. The length of the pulse volume of the sonar at a typical pulse duration of 1 ms is 0.75 m. Obviously, in such cases an echosounder is not able to resolve individual bubbles. But using the basic principle of the remote sensing – incoherent summation of intensities – it is possible to determine the number of scattering objects (bubbles) in the pulse volume of the echosounder. Of course, it is possible, if the scattering abilities of the bubbles are known. Flux estimation with help of backscattering strength is the most used approach applicable to such bubble sources. In the case of identical bubbles with radius r0 total volume flux from the localized bubble jet may be expressed as follows:

Qv 

Nb  all U (r0 )Vb (r0 )  U ( r0 )Vb (r0 ) h  b (r0 )h

(2)

Here: Nb – number of bubbles in the jet with height Δh, U(r) – rise speed of bubble, σb(r) – backscattering cross section of a single bubble, σall – scattering cross section of all bubbles in the jet with height Δh. It is clear, to determine the mass flux the value Qv must be multiplied by density ρ. If Δh is equal to the length of the pulse volume Csτp/2 (Cs – sound speed, τp – pulse duration), σall can be considered as a target strength (TS) of the bubble jet. TS=10log(σall) is the output value of a typical echosounder and is used in numerous investigation for the flux calculation (Greinert, 2006; Lubitsky, 2008 and many other). TS can be correctly measured by a simple single beam sonar only if the position of the target in the directivity pattern (DP) is known. The dual beam sonar is able to determine this position without special maneuvering and calculates TS properly. Usually, split beam sonar is not able to determine the angle position of the multiple target! For the flux estimation the equation similar to Eq.(2) is used, but instead σb(r), U(r) and Vb(r) at equal r = r0 the averaged values are calculated and substituted in Eq.(2). The averaging involves the bubble size distribution and usually is made separately for each function mentioned above. This approach does not allow for a reasonable analysis of calculation errors. Therefore, the question about the accuracy of such estimations remains open. In most cases the resolution volume of the ship mounted echosounder substantially exceeds the size of the jet and may include several jets and/or distributed bubble clouds. Therefore, a more common way to describe the scattering properties of the bubbles escapes is a volume backscattering cross sections σv that depend on spatial coordinates. Obviously, the bubble size distribution (BSD) must be taken into account.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session X: September 4th (13:30-13:50) CALCULATION OF THE GAS FLUX IN THE DENSE BUBBLE JETS AND CLOUDS WITH BROAD BUBBLE SIZE DISTRIBUTION The known experimental BSD (see, for example, Muyakshin and Sauter 2010) sharply drop at r < 0.5–1.0 mm and smoothly decrease at 2 < r < 10 mm. For the further mathematical evaluation it is convenient to introduce the modeling BSD in the following form

N ( r , N 0 )  N 0  exp( r ) if r  rC N (r , N 0 )  0

if 0  r  rC

(3)

Using this approximation we can write the mass flux q per unit area as Eq.(4) and the backscattering cross section per unit volume σv as Eq.(5).

q  g N

4  U (r )r 3 exp( r )dr 0 3  rise rc

(4)

(5) 

r 2 exp( r )dr 2 rc   r  2   res 1   2   r    

v  N  0

Resonant radius rres of the bubble corresponding to working frequency of the sonar f0 (δ – damping const) may be expressed in the form

rres  1 2f

3 ( P  w gh) 0 w 0

(6)

where γ – adiabatic const, ρw – water density. Excluding N0 from Eq.(4) and (5), we obtain linear connection between flux q and volume backscattering strength σv: q   g K ( rc , rres ,  ,  ) v . The calculations at f0 = 38 KHz, h = 1250 m, α = 1.1 1/mm, and rc < rres show about four fold changes in K, namely, from K = 0.96 (m/s)mm at δ = 0.15 and rres = 1.95 mm to K = 4.1 (m/s)mm at δ = 0.35 and rres = 0.92 mm. The variation of α also affect the value of K(…): increasing of α from 1.2 to 1.8 5 1/mm reduce K(…) approximately twice. The method described above takes into account the bubble size distribution. This enabled evaluating the impact of the BSD, the resonance behavior of bubbles, and echosounder frequency on the flux calculations. This approach also enables the estimation of uncertainty in the flux due to the lacks in our knowledge of the real properties of the bubble escapes. In Muyakshin and Sauter (2010), the pulse volume of the sonar at a fixed depth is considered as a twodimensional spatial filter. Namely, the output signal can be expressed in the form: 2 / 2

 v ( X 0 , Y0 , h) 

  0

v

( X 0  h    sin(  ), Y0  h    cos( ), h) 4 ( ) /( 4 (0) * )dd (7)

0

Where: Φ(θ) – directivity pattern of the sonar, θ*<<1 – half width of the DP, h – depth, X0 and Y0 – current position of the ship along survey track. 177

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session X: September 4th (13:30-13:50) This output signal represents not a real but a strongly smoothed distribution of bubbles. Total gas flux over a given study area can be calculated by integrating the smoothed two-dimensional field of backscattering. Practically, it is impossible to measure this field continuously but it can be reconstructed by two-dimensional interpolation using several one-dimensional cross sections obtained during repeated crossings of a bubble release in different directions. Ship mounted multi beam sonar produce 3D picture of the ultrasound backscattering field. Such system enables the quick overview and detection of bubble seeps on the large bottom areas (Nikolovska et al., 2008; Schneider von Deimling et al., 2006). This technique ideally combines with proposed above method based on the area integration of the volume backscattering strength σv. Corresponding processing procedure must be developed in the future. OTHER APPROACHES Bottom mounted horizontally-looking multibeam sonar (operating frequency f0=150 kHz) was used in (Schneider von Deimling et al., 2010) for the long term observation of time variation of the field of the multiple bubble seeps in the North Sea. Mechanically scanning sonar mounted on the ROV (operating frequency 675 kHz, the vertical opening angle 900 and horizontal beam angle 1.40) was used for the quantification of the methane seeps in the eastern Black Sea (Nikolovska et al., 2008). “The acoustic approach from the backscatter data of the sonar resulted in bubble fluxes in the range of 0.01 to 5.5 L/min at in situ conditions (850 m water depth, 90C). Independent flux estimations using a funnel-shaped device showed that the acoustic model consistently produced lower values but the offset is less than 12%”. In this case scanning beam of the echosounder crosses bubble jet and the system determines the horizontal distribution of the scattering in the jet. Further processing is based on integration of this distribution. To reach acceptable accuracy laboratory calibration was used with artificial bubble flow. In both cases the spatial resolution of the sonar system is smaller than spatial size of the jet. Such measurements are possible only in the (close) vicinity of the bubble stream (1-100 m). CONCLUSION Our review shows that the errors of the flux estimations are still very significant. There are the following possibilities for their reduction. 1. Calibration in situ with help of the artificial or natural bubbles source. In the case of natural bubble jet for flux measurements reliable optical methods should be used. 2. Development of methods for measuring the flow based on the results of sensing on 2-3 frequencies. The author hopes to attract attention to these methods and organize field measurements to test and validate them. REFERENCES Ostrovsky I., McGinnis D.F., Lapidus L,and Eckert W. (2008), “Quantifying gas ebullition with echosounder: the role of methane transport by bubbles in medium-sized lake”, Limnology and Oceanography: methods, 6, 105-118 Didenkulov I.N., Muyakshin S.I., Stromkov A.A., Fiks G.E. (2011), “Quantifying of methane emissions from the sediments of shallow reservoirs with echosounder”, Vestnik NNGU, 5(3), 37-44 (in Russian)

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session X: September 4th (13:30-13:50) Muyakshin S. I. and Sauter E. (2010), “The hydroacoustic method for the quantification of the gas flux from a submersed bubble plume”, Oceanology, 50(6), 1045-1051 Granin N.G., Makarov M.M., Muyakshin S.I., Kucher K.M., Granina L.Z. (2012), “Estimation of methane fluxes from bottom sediments of Lake Baikal”, Geo Marine Letter, 32(5-6), 427-436 Greinert J., Artemov Yu., Egorov V. et all (2006), “1300-m-high rising bubbles from mud volcanoes at 2080m in the Black Sea: Hydroacoustic characteristics and temporal variability”, Earth and Planetary Science Letters, 244, 1–15 Lyubitskiy A.A. (2008), “Remote acoustic diagnosis of gas release sources on seabed”, Journal of GEOLOGY, Series B, 31-32, 33-38 Schneider von Deimling J., Greinert J., Chapman N. R., Rabbel W., and Linke P. (2010), “Acoustic imaging of natural gas seepage in the North Sea: Sensing bubbles controlled by variable currents“, Limnol. Oceanogr.: Methods, 8, 155–171 Nikolovska A., Sahling H., and Bohrmann G. (2008), “Hydroacoustic methodology for detection, localization, and quantification of gas bubbles rising from the seafloor at gas seeps from the eastern Black Sea”, G3, 9(10), doi:10.1029/2008GC002118 Schneider von Deimling J., Brockhoff J., Greinert J. (2007), “Flare imaging with multibeam systems: Data processing for bubble detection at seeps”, G3, 8(6), doi:10.1029/2007GC001577

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Seismic Chimneys in the Southern Viking Graben Jens Karstens and Christian Berndt GEOMAR, Helmholtz Centre for Ocean Research, Kiel, Germany [email protected], [email protected] ABSTRACT The interdisciplinary EC-funded research project ECO2 aims to evaluate the influence of leakage from industrial CO2 storage sites on benthic ecosystems. In this context, the analysis of natural fluid flow systems is crucial for the evaluation of the long-term integrity of CO2 storage sites. One of the project’s main study areas is the Southern Viking Graben (SVG), which hosts the longest operating and probably best-studied marine CO2 storage facility at Sleipner. Since 1996 CO2 has been injected into the Utsira Formation, an 850 m deep saline aquifer sealed by the Nordland Shales, which consist of low permeable mudstones (Chadwick et al., 2012). The presence of a multitude of shallow (<1000 m) fluid flow manifestations including vertical fluid conduits, bright spots and mud diapirs in the study area have been reported before (Heggland, 1997). Here, we attempt to reconstruct the evolution of the paleo fluid flow system in the Sleipner area and describe the implications on the long-term integrity performance of the CO2 storage site. The most prominent seismic anomalies in the study area are more than 40 large chimney structures, which suggest a hydraulic connection of deeper stratigraphic levels and the shallow subsurface. These features can be divided into three categories (A, B and C) according to their seismic appearance. Type-A-chimneys are strictly columnar and up to 600 m wide features and may represent exceptionally large pipe structures, which were formed by rapidly ascending gas. Type-B-chimneys have a chaotic and distorted seismic appearance comparable to chimney structures found above leaking gas reservoirs. Type-C has a pronounced elongated shape and shows evidence for sediment mobilization. All three chimney types are most likely the result of overpressure driven hydrofracturing of the overburden, but their different seismic appearances imply different formation parameters, such as timing, activity duration, formation dynamics and involved fluids.

REFERENCES R.A. Chadwick, G.A. Williams, J.D.O. Williams, D.J. Noy, Measuring pressure performance of a large saline aquifer during industrial-scale CO2 injection: The Utsira Sand, Norwegian North Sea, International Journal of Greenhouse Gas Control, Volume 10, September 2012, Pages 374-388 Heggland, R., 1997. Detection of gas migration from a deep source by the use of exploration 3D seismic data. Marine Geology 137, 41–47.

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12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session X: September 4th (14:10-14:30)

AUV Surveys Reveal Seafloor Asymmetric Depressions and Linear Troughs along a Fault Zone Offshore Southwest Taiwan Tzu-Ting Chen and Char-Shine Liu Institute of Oceanography, National Taiwan University, Taipei, Taiwan Charles K. Paull Monterey Bay Aquarium Research Institute, Moss Landing, California, USA ABSTRACT In April 2013, a Taiwan-US collaborative recent cruise was conducted in the area offshore southwest Taiwan. Numerous (over 200) asymmetric seafloor depressions and a series of linear troughs were observed along a west-vergent fault zone on the west side of the Good Weather Ridge utilizing the mapping Autonomous Underwater Vehicle (AUV) of the Monterey Bay Aquarium Research Institute (MBARI). These asymmetric seafloor depressions are distributed over an area of about 1.03 km2 in the eastern part of the surveyed area between 1100 and 1200 m water depths. The zone of depressions occurs near the boundary between the smooth seafloor of sediment basin to the west and the outcrops of a series dipping exposed on a strata sloping seafloor to the east. The unprecedented high-resolution multibeam bathymetry (1 m lateral resolution) and chirp subbottom profiles (11 cm vertical resolution) reveal that the depressions are 1 to 3 m deeper than the surrounding seafloor and form comet-shaped scars of ~10 to 200 m length that widen downslope. Some circular depressions also occur, which would usually be described as pockmarks. Some asymmetric depressions have knickpoints within their scarps, which are horizontally aligned and suggested the existing of some weak planes. Chirp subbottom profiles also show horizontal reflectors, which are parallel with the exposed beds seen in the outcrops above, indicating that these depressions occur where the sediment cover over these beds pinches out. This study implies these asymmetric depressions relate to gas seepage, because the fluid possibly migrate along the lightly dipping horizontal strata and then blowout where seafloor cute the strata that generate these depressions. Furthermore, the side-scan sonar images found a small high amplitude anomalies area around the depressions, showing a strong reflection caused by authigenic carbonates. Seafloor where has authigenic carbonates become firm and roughness causing strong backscatter energy. On the southern partner of the surveyed area, a series of north-south tending troughs occur within a 4.5 km long and 1.5 km wide zone in water depths 975 and 1450 m. Seismic reflection profiles running across the fault zone show that these troughs are developed on top of a small young sediment wedge at the toe of the hanging wall above the west-vergent fault. The sediment of this wedge is uplifted and folded due to the fault activities, and the observed young troughs could be the seafloor expression of the deformation. This study implies these troughs are related to the fault and block movement. However, few areas have been surveyed at this resolution and thus we speculate seafloor asymmetric depressions and seafloor troughs like the descriptions above are not unique in this area. KEYWORDS Autonomous underwater vehicle, high-resolution bathymetry, Good Weather Ridge, gas seep, asymmetric depressions

181

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session X: September 4th (14:30-14:50)

Multi-Frequency Imaging and Quantification of Shallow Free Gas Zsuzsanna Tóth, Volkhard Spiess Department of Geosciences, University of Bremen [email protected]

ABSTRACT Poor signal penetration on acoustic profiles often indicates free gas in marine sediments and it is described as acoustic turbidity or, in case of a zone devoid of reflections, acoustic blanking. In this study, we investigate the edge of a small acoustic blanking zone in the Bornholm Basin (Baltic Sea) using 10 frequency bands of high-frequency sediment echosounders and multichannel seismics, which cover a frequency range between 0.2 and 43 kHz. At the edge of this gassy patch, compressional wave attenuation caused by the presence of free gas bubbles is estimated from reflection amplitudes beneath the gassy sediment layer. The theory of Anderson and Hampton (1980) predicts that gas bubbles resonate at a fundamental frequency related to their size. Based on the multi-frequency seismo-acoustic data, imaging of shallow gas is considerably influenced by the resonance of gas bubbles, because in the resonance frequency range, attenuation is significantly increased. At the resonance frequency of the largest bubbles between 3 and 5 kHz, high scattering causes complete acoustic blanking beneath the top of the gassy sediment layer. In the wider resonance frequency range between 3 and 15 kHz, the effect of smaller bubbles becomes dominant and the attenuation slightly decreases. This allows acoustic waves to be transmitted and reflections can be observed beneath the gassy sediment layer for higher frequencies. When the acoustic wavelength exceeds the size of gas bubbles 'above resonance' (beginning at ~19 kHz), compressional wave attenuation is low and the presence of free gas can be inferred from the decreased reflection amplitudes beneath the gassy layer. Below the resonance frequency range (<1 kHz), attenuation is generally very low and not dependent on frequency. Using the geoacoustic model of Anderson and Hampton (1980), the observed frequency boundaries suggest gas bubble sizes between 1 and 4-6 mm, and gas volume fractions up to 0.0002% in a ~2 m thick sediment layer, whose upper boundary is the gas front. With the multi-frequency acoustic approach, we are able to identify the resonance effects of gas bubbles. Using the Anderson and Hampton model, the size of gas bubbles can be characterized from the frequency boundaries, and free gas content can be estimated from the attenuation caused at resonance at the edge of an acoustic blanking zone. Quantification of free gas in shallow marine environments is therefore possible if the measurement frequency range allows the identification of the resonance frequency peak. The method in this study is limited to places with only moderate attenuation, where the amplitudes of a reflection can be analysed beneath the gassy sediment layer. REFERENCES

Anderson, A. L. and Hampton, L. D. (1980), Acoustics of gas-bearing sediments I-II., J. Acoust. Soc. Am. 67, 1865-1903 182

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session X: September 4th (14:50-15:10)

Influence of 3D Fault Modeling on Gas Migration Pathways and Gas Hydrate Accumulation in Porous Sediments: Case Studies of Hydrate Ridge (Oregon Margin) and Green Canyon (Gulf of Mexico) Ewa Burwicz, Elena Piñero and Christian Hensen GEOMAR Helmholtz Centre for Ocean Research Kiel [email protected], [email protected], [email protected] ABSTRACT In order to evaluate and understand the results of sedimentary basin numerical modeling including nonhomogeneous layer structures (e.g. faults or tectonically active salt domains), it is essential to prescribe clear and scientifically-based rules of fault-like structure implementation. For this purpose, we examine the most important parameters and aspects that influence modeling of fluids and gas migration pathways within porous sedimentary layers, including model resolution, gridding of the fault/salt-edge structure, 3D continuity, fault properties, migration model, timing of opening/closing, etc. The results of series of model-runs covering the common ranges of parameter values reported from natural marine settings will be presented during the conference. Results of the specific modeled configurations for the Green Canyon (Gulf of Mexico) and Hydrate Ridge (Oregon margin) will also be discussed. INTRODUCTION Petroleum modeling systems include the processes of generation, migration and accumulation of hydrocarbon components. In 3D numerical modeling of basin-scale reservoirs, the definition of the fluid migration pathways is crucial to evaluate the charging potential of sedimentary layers. Fluids and gases migrate along relatively high permeability layers or tectonic migration pathways, which include typical faulting structures or edges of salt deposits. In gas hydrate-rich settings, the timing for the migration of gas can have a prominent effect, especially if methane has mostly a thermogenic origin (e.g. Daigle and Dugan, 2010). We propose to investigate the most important parameters used in numerical modeling of common fault-like structures, such as: gridding, permeability contrast with the surrounding sediments, effect of spatial resolution, timing of placement into the model, and, depending on the history of the basin, opening and closing of the structure. FAULT STRUCTURE IMPLEMENTATION Numerical simulations often face a problem regarding transport efficiency of fluid and gas components. In order to solve and upgrade these processes, petroleum software applications (e.g. PetroMod, Schlumberger) typically have the option to introduce faults and fault-like structures into the mesh-gridded modeling areas. However, these numerical platforms offer some ready-to-use solutions, which need to be carefully tested with respect to the meaning and implications of the results. What could provide an efficient tectonic migration pathway in numerical modeling? In the presentation, we will focus on two main kinds: faults and salt edges along diapir structures. Faults and salt edges can be easily identified on seismic records. After careful interpretation, these surfaces can be implemented into the 3D stratigraphic model domain (Fig. 1). 183

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session X: September 4th (14:50-15:10)

Fig. Left: Numerical implementation of deeply-rooted (outer part of modeling domain) and shallow fault (central part of modeling domain) structures and edges of salt deposit as potential migration pathways for gas originating from thermal cracking of organic-rich sediments (based on numerical model of the Green Canyon site, Gulf of Mexico). Right: Numerical implementation of shallow faults as potential migration pathways for gas from Horizon A up to the Gas Hydrate Stability Zone (GHSZ) and the seabed (based on numerical model of the Hydrate Ridge, Oregon margin). What shall be considered before fault structure implementation into numerical simulation? Several parameters and aspects influence the implementation of the tectonic structures, such as: - model resolution and mesh-gridding: the size of the gridded cells determines the minimum size of the structure affecting the model - 3-D structure: discontinuity of structures will increase any edge effect produced in the simulation - timing: closing/opening of the structure resolved for the history of the basin - migration properties (e.g. permeability): fault properties can be homogeneous or heterogeneous, defined according to several parameters such as permeability, capillary pressure, shale ratio, etc. - migration method: Darcy’ flow, FlowPath (PetroMod), etc. EVALUATING THE RESULTS There are several output parameters that enable the identification of correctly or incorrectly implemented and parameterized fault and salt edge structures, these include: - migration pathways (Fig. 2) - fault saturation (changing with a history of a basin)

- direct impact on gas and gas hydrate accumulations (timing of hydrocarbon migration and accumulation)

184

12th International Conference on Gas in Marine Sediment, September 1-6, 2014 Oral Session X: September 4th (14:50-15:10)

Fig. 2: The impact of faults and salt edges (colored areas) introduced into numerical model on migration pathways (drainage areas, black lines), based on numerical model of the Green Canyon site, Gulf of Mexico. CONCLUSIONS Tectonic structures play an important role in the migration of fluids and gas and therefore, they need to be correctly implemented into 3D basin-scale models. The main parameters and aspects affecting fault structure implementation in models include model resolution, gridding of the structure, time and space continuity, migration properties, as well as the migration method. In gas hydrate-rich settings, timing of gas migration is crucial for the correct modeling of gas hydrates accumulation. A good understanding of the modeling options used in 3-D fault-like structure implementation is crucial for achieving meaningful model results. During the conference, we will describe the modeling parameters of first- and second-degree importance which influence the migration pathways of fluid and gas phases co-existing in the porous media. ACKNOWLEDGEMENTS We thank Statoil ASA for providing the seismic data from the Green Canyon site, Gulf of Mexico as well as additional modeling data sets necessary for setting up numerical simulations and Schlumberger Aachen for providing the PetroMod modeling software.

REFERENCES Daigle, H., Dugan, B. (2010), Origin and evolution of fracture-hosted methane hydrate deposits. Journal of Geophysical Research Vol. 115 B11103, doi: 10.1029/2010JB007492.

185

12th International Conference on Gas in Marine Sediments Taipei, Taiwan, September 1-6, 2014 Author Index First name

Family name

Abstract No.

Page

Boris

Baranov

GIMS12A045

61

GIMS12A023

92

Tzu-Ting

GIMS12A088

4

Po-Chun

GIMS12A007

Christian

Jean-Philippe

Ewa

Berndt

Blouet

Burwicz-Galerne

First name

Family name

Abstract No.

Page

GIMS12A001

85

Chen

GIMS12A082

181

Chen

GIMS12A085

6

9

GIMS12A029

46

GIMS12A005

17

GIMS12A089

52

GIMS12A034

54

GIMS12A037

94

GIMS12A057

107

GIMS12A055

99

GIMS12A050

165

GIMS12A024

123

GIMS12A061

180

Liwen

Chen

GIMS12A049

130

GIMS12A093

81

Hsuan-Wien

Chen

GIMS12A051

80

GIMS12A091

126

Min-Te

Chen

GIMS12A066

147

GIMS12A094

139

Nai-Chen

Chen

GIMS12A085

6

GIMS12A047

128

GIMS12A062

64

GIMS12A040

183

GIMS12A013

78

Tin-Yam

Chan

GIMS12A015

36

GIMS12A001

85

Ching-Tse

Chang

GIMS12A009

31

GIMS12A064

86

Chia-Hsien

Chao

GIMS12A017

39

GIMS12A002

26

Hung-I

Chao

GIMS12A072

154

GIMS12A016

38

Duofu

Chen

GIMS12A010

32

GIMS12A038

59

GIMS12A011

34

GIMS12A054

98

GIMS12A018

41

Che-Kang

Chu

GIMS12A037

94

GIMS12A021

87

San-Hsiung

Chung

GIMS12A085

6

GIMS12A022

88

GIMS12A029

46

GIMS12A030

89

GIMS12A089

52

GIMS12A008

90

GIMS12A055

99

Win-Bin

Wan-Yen

Cheng

Cheng

Sheng-Chung

Chen

GIMS12A004

30

Marc

De Batist

GIMS12A059

171

Song-Chuen

Chen

GIMS12A002

26

Matthieu

Dupuis

GIMS12A039

116

GIMS12A029

45

GIMS12A077

118

GIMS12A089

52

Alexander

Egorov

GIMS12A043

112

GIMS12A013

78

Dong

Feng

GIMS12A010

32

First name

Family name

Abstract No.

Page

GIMS12A011

34

First name

Family name

Abstract No.

Page

GIMS12A017

39

Hongxiang

Guan

GIMS12A011

34

Elodie

Lebas

GIMS12A057

107

Ruei-Long

Guo

GIMS12A044

64

Hsiao-Fen

Lee

GIMS12A069

50

Akihiro

Hachikubo

GIMS12A033

91

GIMS12A076

51

GIMS12A023

92

Ke-Shu

Li

GIMS12A080

159

Akihiro

Hiruta

GIMS12A013

78

Wei-Zhi

Liao

GIMS12A053

97

Sutieng

Ho

GIMS12A093

81

Ying-Chih

Liao

GIMS12A078

155

GIMS12A091

126

Saulwood

Lin

GIMS12A085

6

GIMS12A094

139

GIMS12A005

17

Bieng-Zih

Hsieh

GIMS12A079

134

GIMS12A004

30

Huai-Houh

Hsu

GIMS12A016

38

GIMS12A017

39

Yu-Chun

Huang

GIMS12A062

64

GIMS12A029

45

GIMS12A001

85

GIMS12A089

52

GIMS12A046

58

GIMS12A038

59

GIMS12A062

64

GIMS12A044

64

GIMS12A058

164

GIMS12A013

78

Chin-Chang

Hung

Sandra

Hurter

GIMS12A012

35

GIMS12A001

85

Patrice

Imbert

GIMS12A093

81

GIMS12A064

86

GIMS12A039

116

GIMS12A054

98

GIMS12A077

118

GIMS12A024

123

GIMS12A091

126

GIMS12A084

163

GIMS12A094

139

GIMS12A044

69

GIMS12A069

50

GIMS12A052

75

GIMS12A076

51

Yu-Shih

Lin

GIMS12A044

69

GIMS12A026

56

Li-Lian

Liu

GIMS12A017

39

GIMS12A061

180

Char-Shine

Liu

GIMS12A002

26

GIMS12A087

3

GIMS12A029

45

GIMS12A003

7

GIMS12A089

52

GIMS12A007

9

GIMS12A053

97

GIMS12A005

17

GIMS12A049

130

GIMS12A034

54

GIMS12A080

159

GIMS12A050

165

GIMS12A082

181

GIMS12A034

54

Hsuan

Lo

GIMS12A072

154

GIMS12A020

76

Mikhailovich

Makarov

GIMS12A056

103

GIMS12A050

165

Ryo

Matsumoto

GIMS12A090

111

Hirotsugu

Minami

GIMS12A045

61

GIMS12A033

91

Li-Hsin

Jens

Miriam

Ingo

Stephanie

Kao

Karstens

Kastner

Klaucke

Koch

Roza

Kruglyakova

GIMS12A065

142

Mei-Chin

Lai

GIMS12A004

30

Li-Hung

Lin

First name

Sergey

Family name

Muyakshin

Abstract No.

Page

GIMS12A023

92

GIMS12A056

103

GIMS12A048

First name

Abstract No.

Page

GIMS12A062

64

GIMS12A085

6

175

GIMS12A002

26

Yunshuen

Family name

Wang

Ardian

Nengkoda

GIMS12A081

138

GIMS12A029

46

Anatolii

Obzhirov

GIMS12A025

11

GIMS12A089

52

GIMS12A045

61

GIMS12A052

75

GIMS12A019

70

GIMS12A053

97

GIMS12A033

91

GIMS12A055

99

GIMS12A023

92

GIMS12A049

130

GIMS12A069

50

GIMS12A076

51

Catherine

Pierre

GIMS12A032

122

Hsin-Yi

Wen

Ian

MacDonald

GIMS12A063

5

Heiko

Sahling

GIMS12A003

7

Wen J

Whan

GIMS12A006

19

Yuji

Sano

GIMS12A092

23

Daidai

Wu

GIMS12A027

42

GIMS12A076

51

Shein-Fu

Wu

GIMS12A070

153

Sudipta

Sarkar

GIMS12A050

165

Jyun-Yi

Wu

GIMS12A067

152

Yota

Sasaki

GIMS12A023

92

Cheng-Yueh

Wu

GIMS12A079

134

Wu-Yang

Sean

GIMS12A071

131

Chien-Hui

Yang

GIMS12A015

36

Pavel

Serov

GIMS12A031

173

Tsanyao Frank

Yang

GIMS12A085

6

GIMS12A036

174

GIMS12A009

31

Renat

Shakirov

GIMS12A025

11

GIMS12A069

50

So-Siou

Shu

GIMS12A073

148

GIMS12A076

51

Glen

Snyder

GIMS12A083

124

GIMS12A038

59

Evan

Solomon

GIMS12A074

109

GIMS12A062

64

Kamila

Sztybor

GIMS12A035

125

GIMS12A044

64

Martin

Hovland

GIMS12A014

68

GIMS12A052

75

Zsuzsanna

Tóth

GIMS12A086

167

GIMS12A013

78

GIMS12A060

182

GIMS12A001

85

Lisa

Vielstädte

GIMS12A026

56

GIMS12A064

86

Shuhong

Wang

GIMS12A028

44

GIMS12A084

163

Qinxian

Wang

GIMS12A018

41

Tsung-Han

Yang

GIMS12A064

86

Chau-Chang

Wang

GIMS12A046

58

Timo

Zander

GIMS12A007

9

GIMS12A034

54

Organized by Department of Geosciences, National Taiwan University (NTU) Co-organized by: Institute of Earth Sciences, Academia Sinica Taiwan Ocean Research Institute, NARL Department of Earth Sciences, National Central University (NCU) Exploration & Development Research Institute, Chinese Petroleum Corporation (CPC) Institute of Marine Geology and Chemistry, National Sun Yat-sen University (NSYSU) Department of Life Sciences, National Chung Hsing University (NCHU) Institute of Oceanography, National Taiwan University (NTU) Institute of Applied Marine Physics and Undersea Technology, National Sun Yat-sen University (NSYSU) Institute of Applied Geosciences, National Taiwan Ocean University (NTOU) Central Geological Survey, MOEA Department of Earth Science, National Cheng Kung University (NCKU) Geological Society located in Taipei Chinese Geoscience Union Sponsored by Ministry of Science and Technology