University of Sulaimani College of Science Department of Geology
Well Logging Course Book B.Sc. 4th Stage, Geology Academic Year 2015- 2016
Contents Course coordinator List of Lectures of the Course Course overview Course Objectives Course References Subjects Syllabus Exams
Course coordinator and list of teachers on this course 1- Name of the Course: Well Logging 2- Lecturer: Dr. Fouad M. Qader 3- Department\ Branch and the college: College of Science/ Geology 4- Contacts: - Address: - E-mail:
[email protected] [email protected] Tel: 07701494343
Course Overview Well Log … The most appropriate name is Wireline geophysical well log. Conveniently shortened to well – log or log. Well logging is the process of recording various physical, chemical, electrical, or other properties of the rock/fluid mixtures penetrated by drilling a well into the earth's mantle. As logging tools and interpretive methods are developing in accuracy and sophistication, they are playing an expanded role in the geological decisionmaking process. Today, petrophysical log interpretation is one of the most useful and important tools available to petroleum geologist. Besides their traditional use in exploration to correlate zones and to assist with structure and isopach mapping, logs help geologist to define physical rock characteristics such as lithology, porosity, pore geometry, and permeability. Logging data are used to identify productive zones, to determine depth and thickness of zones, to distinguish between oil, gas, or water in reservoir, and to estimate hydrocarbon reserves. Also, geologic maps developed from log interpretation help with determining facies relationships and drilling locations.
Well Logging course includes: The course of well logging includes: 1. Theoretical lectures (2 hours per a week) for fifteen weeks (30 hours per the course). 2. Practical lectures (3 hours-lectures per a week) for 15 weeks. 3. At least one field trip to an oil rig site to see the drilling operation and be familiar with the well log devices.
Course objectives The important goal of teaching well logging course is to provide the students with a comprehensive knowledge of the principal techniques of well logs, and their interpretations. This course will provide a foundation for understanding of the well logging types and their works. By the end of the course, the student is expected to be able to: 1. Become familiar with log types and their techniques. 2- The mechanism of wireline log running, and the function of each log. 3. Measurement of the well log data with their units. 4- Interpretation of the log curves and their behaviors opposite the different subsurface geolological conditions. 5- Estimation of the essential reservoir parameters from logs such as lithology, borehole condition, porosity, permeability, fluid saturations, etc….
Course references 1- The Geological Interpretation of well logs (2000), Malcolm Rider (second edition), Whittles Publishing. 2- Basic Well Log Analysis, (2004), George Asquith and Daniel Krygowski, (second edition), AAPG.
Useful References and sites: 1- Principles of Wireline Logging Technology, China National Logging Corporation (CNLC). 2- Log Analysis of Subsurface Geology (1985) John H. Doveton. 3- Well Logging for Earth Scientists, 2nd Edition (2008), by Darwin V. Ellis and Julian M. Singer. 4- Well Logging and Formation Evaluation (2005), by Toby Darling. Useful sites: http//geology.uprm.edu http/www.osun.org http//www.springerlink.com
Syllabus No. 1 2 3 4 5 6 7
8 9 10 11 12 13
Title of the Subject Lecturer's/Tutor's Name Introduction Dr. Fouad M. Qader Borehole environment Dr. Fouad M. Qader Gamma ray logs Dr. Fouad M. Qader Dr. Fouad M. Qader Porosity logs: - Sonic logs Dr. Fouad M. Qader - Density log Dr. Fouad M. Qader - Neutron log Dr. Fouad M. Qader Self potential SP logs Dr. Fouad M. Qader Midterm exam Resistivity and conductivity logs: Dr. Fouad M. Qader - The Laterolog Dr. Fouad M. Qader - Induction Logs Dr. Fouad M. Qader - Microresistivity Logs Dr. Fouad M. Qader Dipmeter log Dr. Fouad M. Qader Quick look methods Dr. Fouad M. Qader Image logs Dr. Fouad M. Qader End-term exam
Subjects: Subject 1: Introduction Lecturer: Instructor Dr. Fouad M. Qader Objective: To give the student a basic knowledge regarding the history of well logging and the general definitions of well log, their terms and classification of well logging tools.
Scientific contents
-
Historical View
-
Definitions
-
Classification of well log and general well logging terms
Subject-2: borehole environment + Caliper Log To give the student a basic information regarding the conditions surrounding the borehole which they are created as a result of drilling operations, and their effects on log measurements. Scientific contents:
-
Invasions
-
Drilling mud
-
Some property of formation surrounding the wells which affect logging measurement
- Caliper Log
references 1- The Geological Interpretation of well logs, Malcolm Rider ( page 1-18) 2- Basic Well Log Analysis, (page 1-10), 3- Principles of Wireline Logging Technology,( page 1-67).
Subject-3: Gamma Ray Logs To give the student a principle techniques of the Gamma Ray logs, their types, qualitative and quantitative uses of them.
Scientific contents:
- Natural Gamma Ray log (GR), its measurement, track, unit - Qualitative use: (its behavior against various lithologies). - Quantitative use (calculation of shale content Vsh%). - Natural Gamma Ray Spectrometry (NGS) - Uranium curve, Thorium curve, Potassium curve, and their units, tracks and their uses as indicator of depositional environment, facies condition, clay type.
references 1- The Geological Interpretation of well logs, Malcolm Rider ( page 67-86) 2- Basic Well Log Analysis, (page 31-32), 3- Principles of Wireline Logging Technology,( page 88-90).
Subject-4: Porosity logs :– a- Sonic Log To give the student a principle techniques of the sonic log, qualitative and quantitative uses of them.
Scientific contents:
- Sonic log, its technique, unit, measurement - Log curve's behavior opposite various type of rock. - Derived Porosity from sonic log (Фs), its equations and parameters.
references 1- The Geological Interpretation of well logs, Malcolm Rider ( page 91109) 2- Basic Well Log Analysis, (page 37-39), 3- Principles of Wireline Logging Technology,( page 118-131).
Subject-5: Porosity logs :– b- Density Log To give the student a principle techniques of the Density log, qualitative and quantitative uses of them.
Scientific contents:
- Density log, its technique, unit, measurement - Log curve's behavior opposite various type of rock. - Derived Porosity from Density log (ФD), its equations and parameters.
references 1- The Geological Interpretation of well logs, Rider ( page 113-131) 2- Basic Well Log Analysis, (page 39-40). 3- Principles of Wireline Logging Technology,( page 103).
Subject-6: Porosity logs:– c- Neutron Log To give the student a principle techniques of the Neutron log, qualitative and quantitative uses of them.
Scientific contents:
- Neutron log, its technique, unit, measurement
- Log curve's behavior opposite various type of rock. - Porosity measuring from Neutron log (ФN). - Neutron-Density combination porosity (ФN-D), average porosity. - Uses of Neutron-Density combination to derive an average porosity, distinguish of gas zone, lithology identification, and porosity cross plot.
references 1- The Geological Interpretation of well logs, Rider ( page 133-147) 2- Basic Well Log Analysis, (page 41). 3- Principles of Wireline Logging Technology,( page 95).
Subject-7:– Self potential (SP) log This lecture gives the student a principle of SP log and its significant role in formation evaluation including detect permeable beds, boundaries of permeable beds, determination formation water resistivity, (Rw), also determine of shale in permeable beds. Scientific contents:
- The principle technique of SP log, - The use of this log, - Interpretation of various deflections of SP curve and the subsurface factors response to suppressed the deflections.
references 1- The Geological Interpretation of well logs, Malcolm Rider ( page 33-39) 2- Basic Well Log Analysis, (page 21-24), 3- Principles of Wireline Logging Technology, (page 69-85).
Subject-8, 9:– Resistivity and conductivity logs: To give the student a principle technique to the work of the resistivity logs, their types and uses, especially in determine hydrocarbon-bearing versus water-bearing zones.
Scientific contents:
- The resistivity log, -
the resistivity of the materials,
- borehole condition, three main branches of resistivity logging (Laterolog, Induction Logs, - Microresistivity Logs), - Qualitative uses of resistivity logs, - The Theoretical patterns of Rxo, Ri and Rt.
references 1- The Geological Interpretation of well logs, Malcolm Rider ( page 42-58) 2- Basic Well Log Analysis, (page 77-86), 3- Principles of Wireline Logging Technology,( page 140-157). Subject-10:– Dipmeter log To give the student a principle techniques of the dipmeter log, qualitative and quantitative uses in Structural geology (structural attitude; dip, unconformities, faults, folds,
fractures),
Sedimentary geology (Sedimentary structure,
Paleocurrent analysis, Reservoir orientation, facies characterization. In addition to hole position, size, shape and breakout
Scientific contents:
- The Dipmeter, -
Principal uses,
-
Log Presentation,
- and additional plots
References 1- The Geological Interpretation of well logs, Rider ( page 169-198) 2- Principles of Wireline Logging Technology,( page 167-1178).
Subject-11:– Quick look methods Quick look methods are helpful to geologist because they provide flags, or indicators, that point to possible hydrocarbon zones requiring further investigation.
Scientific contents: four quick-look methods will discuss:
- Rxo/Rt -
Apparent water resistivity (Rwa).
- Conductive-derived porosity. - Wet resistivity (Ro).
Reference Basic Well Log Analysis, (page 117-120).
Subject-12:– Image logs Borehole images are electrical picture of the rocks and fluids encountered by wellbore. Such images are made by electrical, acoustic, or video devices which have been lowered into the well. This lecture provides a guide to the acquisition, processing, and interpretation of borehole images. Scientific contents:
-
Electrical Borehole Images.
-
Acoustic Borehole Images.
- Downhole Video Images.
Reference 1- Basic Well Log Analysis, (page 151-156).
2- Principles of Wireline Logging Technology,( page 213-244).
Type and samples of the exams 1. Multiple choice questions. Examples: Fill the following blanks with the suitable words or terms in the brackets:
1- To increase a mud weight, the …… added into the drilling mud.
(Barite ; Tuff ;
Mica). 2- The Sonic derived porosity greater than the actual porosity, if the reservoir contain ………
( Water ;
Oil ;
Gas ).
3- 3ppm of U, 6ppm of Th, and 1% K, will give around …….. of Gamma ray radiations. (64 API ;
30 API ;
50 API).
4- The Density log shows the negative porosity opposite the … … … rocks. (Salt ;
Sandstone ;
Anhydrite).
5- In the clastic rocks, the GR measurement increase with ……….. the grain size. (Increasing ;
Decreasing ;
roundness).
2. True and false questions. Examples: ( √ ) 1- The most appropriate name of well logs is Wireline geophysical well log. ( Х ) 2- In general the log run while drilling. ( Х ) 3- The logs are run (record) while the tools are lowering down in the borehole. ( √ ) 4- The formation of mud cake on the hole's wall is good indication of permeable zone. ( Х ) 5- To control the losses problem in well, the heavy materials added into the drilling mud. ( Х ) 6- If the two rock units have the same GR values, it means they contain a same amount of shale. ( √ ) 7- The Resistivity logs affected by drilling mud and invasion zones more than other logs. ( √ ) 8- The sonic velocity of dens Anhydrite is 20000ft/sec. which is equal to 50 µsec/ft. ( Х ) 9- 5 ppm U, 4 ppm Th and 1% K, equivalent to 100 API radiations on SGR. ( √ ) 10- The salt intervals indicated from density log by high porosity.
3. Fill in the blanks questions. Examples:
Complete the following text 1- The SP log is a measurement of the natural potential differences between an electrode in the borehole and the reference electrode at the surface. 2- The relations between Rmf and Rw have a great effect on SP deflection, if Rmf = Rw the SP shows no deflection. 3- The SP shows its maximum deflection against thick, shale free sandstone zone. 4- The SP does show its full deflection if: a- The bed is not thick enough. b- The invasion is very deep. c- There is shale in the formation. d- The adverse lithological effects. e- Hydrocarbons are present. 5- Flushed zone resistivity (Rxo) measured by a group of tools include:
Micro log
(ML), Microlateralog (MLL), Prximitylog (PL), Microspherically focused log (µSFL).
6- Lateral logs should be used when the following conditions exist: a- There is seawater or brine mud in the hole; b- The Rmf / Rw ratio is less than 2.5; c- Formation resistivities exceeds the limits of the induction tool ( >200Ωm ),
d- Bed thickness is less than 10 ft. 7- The behavior of the DLL – MSFL in zone of movable hydrocarbons with quicklook indicated by : RLLD > RLLS > RµSFL (or Rt > Ri > Rxo ).
8- On the micro-log, permeable zones show up when the micro-normal curve reads higher resistivity than the micro-inverse curve, this known as positive separation. . 9- The normal compaction trend of shale can be followed on resistivity log, as compaction increase the resistivity increase. 10- The channel fill sediments indicated from dipmeter by decreasing dip upward which called Red pattern. 11- Archie formula for water saturation of uninvaded zone is: Sw = [(a*Rw)/ (Rt*Φm)] 1/n
4. Definitions. Examples: Define the following well logging terms:
(Well log), (Invasion zone), (Spontaneous logs), (NGS), (Tadpole). 5. Discussions. Example:
Show and discuss the behavior of the following log curves against the subsequent subsurface
conditions
1- GR and SP logs ... … … … against Shale intervals. 2- Dip meter log … … … … … against Structural dip of bedding plane. 3- Deep resistivity logs … against fining upward sandstone hydrocarbon bearing zone. 4- Neutron and Density logs … … …. Against porous limestone bed. 5- Resistivity Minilog log (micro-normal and micro-inverse.) … against
Permeable zone.
6. Explain the reasons of the following; Example:
1. Density log shows Ф, higher than the actual porosity against gas bearing zones. Answer: Gas decreases the bulk density of the rock and make the density higher. 2.Some clean sandstone characterized by high GR Answer: Such sandstone comprise K-Feldspar, which it is radioactive element.
3. SP log shows no deflection if the Rmf=Rw Answer: There is no difference between the salinity of drilling mud with the salinity of formation water, so no moving of ions occurs, and no electrical current. 4.Alongside the dens (non porous) rock intervals, there are no separations among Resistivity log curves. Answer: Because in the dense rock (non porous & non permeable); the contamination zone do not created.
7. Compositional questions. Examples: a. Mention the causes of negative porosity derivation by density log. b. Differentiate (in a table) between SP and GR logs. Or Rxo and Rt c. Explain the log methods to porosity measurement. 8. Real curve log explanations: a. Draw the SP and Resistivity curves opposite the rock column corresponding to their subsurface conditions, (if Rmf > Rw), mention the type of resistivity tools which are used to measure each of the Rxo and Rt., and complete the figure with scales, units … etc.
b. Illustrate the attitude of the subsurface rock layers along the well section, with tadpole symbol in the right space track.
c. From the following Log curves, read each of the GR, ∆t, ρb, and NΦ values at the denoted depth, and then calculate both sonic and density porosities(Φs & ΦD), using their equations, and discuss the results. Raw Data Depth m 1830
ρb
GR 23
Porosity Equations:-
2.44
φD =
ρ ma − ρ b ρ ma − ρ f
∆t 67
NΦ 0.16
φD =
Limestone ΦD 0.1677 bulk porosity
2.71 − 2.44 = 0.1677 2.71 − 1.1
Φs (Wyllie) Limestone 0.14 primary porosity
φS =
If ∆t ma = 47.6 μs/ft and ∆t f = 185 μs/ft
If
∆tlog − ∆tma ∆t f − ∆tma
Pma = 2.71 g/cm3 and ρf=1.1 g/cm3
φS =
67 − 47.6 = 0.14 185 − 47.6
SP - 3 0
1000
I10I mv 0.1
3 0
1000
..... LLD ---- MSFL 1.0 10.0
d- Give your interpretation on 100.0
the labeled logged well section, support your discussion by log
1010
1010
indication, and focus on the following points:
1020
1020
1- Log type and their function. 2- Thickness of the permeable
1030
1030
zone, 3- Is the permeable zone oil
1040
1040
bearing or water? 4- Type of drilling mud, fresh or
1050
1050
saline mud? 5- Estimate the log measurements at the depth of 1016m.
