1. WELL LOGS
Interpreting Geophysical Well Logs
Prof. Dr. Hassan Z. Harraz

2. Historical Aspect
-Schlumberger brothers, Conrad and Marcel, are credited with
inventing electrical well-logs.
- On September 5, 1927, the first “well-log” was created in a
small village named Pechelbroon in France.
- In 1931, the first SP (spontaneous potential) log was
recorded. Discovered when the galvanometer began “wiggling”
even though no current was being applied.
-The SP effect was produced naturally by the borehole mud at
the boundaries of permeable beds. By simultaneously
recording SP and resistivity, loggers could distinguish between
permeable oil-bearing beds and impermeable nonproducing
beds.

3. Types of Logs
a) Gamma Ray
b) SP (spontaneous potential)
c) Resistivity (Induction)
d) Sonic
e) Density/Neutron
f) Caliper

4. a) Gamma Ray
• The gamma ray measures the natural
radioactivity of the rocks, and does not
measure any hydrocarbon or water present
within the rocks.
• Shales: radioactive potassium is a common
component, and because of their cation
exchange capacity, uranium and thorium are
often absorbed as well.
• Therefore, very often shales will display high
gamma ray responses, while sandstones and
limestone will typically show lower responses.

5. • The scale for GR is in API (American
Petroleum Institute) and runs from 0-125
units. There are often 10 divisions in a GR
log, so each division represents 12.5 units.
• Typical distinction between between a
sandstone/limestone and shale occurs
between 50-60 units.
• Often, very clean sandstones or carbonates
will display values within the 20 units range.

6. b) SP (Spontaneous Potential)
• The SP log records the electric potential
between an electrode pulled up a hole and a
reference electrode at the surface.
• This potenital exists because of the
electrochemical differences between the
waters within the formation and the drilling
mud.
• The potenital is measured in millivolts on a
relative scale only since the absolute value
depends on the properties of the drilling mud.

7. • In shaly sections, the maximum SP response to
the right can be used to define a “shale line”.
• Deflections of the SP log from this line indicates
zones of permeable lithologies with interstitial
fluids containing salinities differing from the
drilling fluid.
• SP logs are good indicators of lithology where
sandstones are permeable and water saturated.
• However, if the lithologies are filled with fresh
water, the SP can become suppressed or even
reversed. Also, they are poor in areas where
the permeabilities are very low, sandstones are
tighly cemented or the interval is completely
bitumen saturated (ie- oil sands).

8. c) Resistivity (Induction)
• Resistivity logs record the resistance of
interstitial fluids to the flow of an electric
current, either transmitted directly to the rock
through an electrode, or magnetically induced
deeper into the formation from the hole.
• Therefore, the measure the ability of rocks to
conduct electrical currents and are scaled in
units of ohm-meters.
• On most modern logs, there will be three
curves, each measuring the resistance of
section to the flow of electricity.

9. • Porous formations filled with salt water (which is
very common) have very low resistivities (often
only ranging from 1-10 ohms-meter).
• Formations that contain oil/gas generally have
much higher resisitivities (often ranging from 10-
500 ohms-meter).
• With regards to the three lines, the one we are
most interested in is the one marked “deep”. This
is because this curve looks into the formation at a
depth of six meters (or greater), thereby
representing the portion of the formation most
unlikely undisturbed by the drilling process.
• One must be careful of “extremely” high values, as
they will often represent zones of either anhydrite
or other non-porous intervals.

10. d) Sonic
• Sonic logs (or acoustic) measure the porosity
of the rock. Hence, they measure the travel
time of an elastic wave through a formation
(measured in ∆T- microseconds per meter).
• Intervals containing greater pore space will
result in greater travel time and vice versa for
non-porous sections.
• Must be used in combination with other logs,
particularly gamma rays and resistivity,
thereby allowing one to better understand the
reservoir petrophysics.

11. e) Density/Neutron
• Density logs measure the bulk electron density of the
formation, and is measured in kilograms per cubic meter
(gm/cm3 or kg/m3).
• Thus, the density tool emits gamma radiation which is
scattered back to a detector in amounts proportional to the
electron density of the formation. The higher the gamma
ray reflected, the greater the porosity of the rock.
• Electron density is directly related to the density of the
formation (except in evaporates) and amount of density of
interstitial fluids.
• Helpful in distinguishing lithologies, especially between
dolomite (2.85 kg/m3) and limestone (2.71 kg/m3).

12. • Neutron Logs measure the amounts of
hydrogen present in the water atoms of a
rock, and can be used to measure porosity.
This is done by bombarding the the formation
with neutrons, and determing how many
become “captured” by the hydrogen nuclei.
• Because shales have high amounts of water,
the neutron log will read quite high porosities-
thus it must be used in conjunction with GR
logs.
• However, porosities recorded in shale-free
sections are a reasonable estimate of the
pore spaces that could produce water.

13. • It is very common to see both neutron
and density logs recorded on the same
section, and are often shown as an
overlay on a common scale (calibrated
for either sandstones or limestone’s).
• This overlay allows for better
opportunity of distinguishing lithologies
and making better estimates of the true
porosity.
* When natural gas is present, there
becomes a big spread (or crossing) of
the two logs, known as the “gas effect”.

14. f) Caliper
• Caliper Logs record the diameter of the hole.
It is very useful in relaying information about
the quality of the hole and hence reliability of
the other logs.
• An example includes a large hole where
dissolution, caving or falling of the rock wall
occurred, leading to errors in other log
responses.
• Most caliper logs are run with GR logs and
typically will remain constant throughout.

15. WELL LOG
(The Bore Hole Image)
Interpreting Geophysical Well Logs
Prof. Dr. Hassan Z. Harraz

16. What is well Logging
Well log is a continuous record of measurement made in bore hole respond to
variation in some physical properties of rocks through which the bore hole is drilled.
Traditionally Logs are display on girded papers shown in figure.
Now a days the log may be taken as films, images, and in digital format.

17. HISTORY
 1912 Conrad Schlumberger give the idea of using electrical measurements to map subsurface
rock bodies.
 in 1919 Conrad Schlumberger and his brother Marcel begin work on well logs.
 The first electrical resistivity well log was taken in France, in 1927.
 The instrument which was use for this purpose is called SONDE, the sond was stopped at
periodic intervals in bore hole and the and resistivity was plotted on graph paper.
 In 1929 the electrical resistivity logs are introduce on commercial scale in Venezuela, USA and
Russia
 For correlation and identification of Hydrocarbon bearing strata.
 The photographic – film recorder was developed in 1936 the curves were SN,LN AND LAT
 The dip meter log were developed in 1930
 The Gamma Ray and Neutron Log were begin in 1941

18. LOGGING UNITS
• Logging service companies utilize a variety of
logging units, depending on the location
(onshore or offshore) and requirements of the
logging run. Each unit will contain the
following components:
• logging cable
• winch to raise and lower the cable in the well
• self-contained 120-volt AC generator
• set of surface control panels
• set of downhole tools (sondes and cartridges)
• digital recording system

19. Work Flow Chart

21. From Warrior Energy Services Website, www.warriorenergyservices.com

22. TYPICAL WIRELINE TRUCK
From Welaco

23. TYPICAL WIRELINE SKID UNIT
Welaco Unit at Ormat’s Puna Geothermal Venture in Hawaii

24. TYPES OF LOGS
• Geophysical Logs
– Resistivity
– Porosity
– Gamma Ray
– Dip Meter
– Borehole Imaging
– Other
• Production Logging
– Pressure
– Temperature
– Spinner
– Fluid Density
• Well Inspection
– Sonic
– Caliper
– Electro-magnetic
– Ultrasonic
– RA Tracer
– Video

25.  depth to lithological boundaries
 lithology identification
 minerals grade/quality
 inter-borehole correlation
 structure mapping
 dip determination
 rock strength
 in-situ stress orientation
 fracture frequency
 porosity
 fluid salinity

26. Depth Of Investigation Of Logging Tools

27. LOG INTERPRETATION OBJECTIVES
• The objective of log interpretation depends very much on the user. Quantitative analysis of well
logs provides the analyst with values for a variety of primary parameters, such as:
• porosity
• water saturation, fluid type (oil/gas/water)
• lithology
• permeability
• From these, many corollary parameters can be derived by integration (and other means) to arrive
at values for:
• hydrocarbons-in-place
• reserves (the recoverable fraction of hydrocarbons in-place)
• mapping reservoir parameters
• But not all users of wireline logs have quantitative analysis as their objective. Many of them are
more concerned with the geological and geophysical aspects. These users are interested in
interpretation for:
• well-to-well correlation
• facies analysis
• regional structural and sedimentary history
• In quantitative log analysis, the objective is to define
• the type of reservoir (lithology)
• its storage capacity (porosity)
• its hydrocarbon type and content (saturation)
• its producibility (permeability)

28. POROSITY LOGS
• Neutron tool
– Neutron source
– High energy neutrons are slowed down by hydrogen atoms in
water (or oil) and detected by tool
– Porosity is function rock type and slow neutron count
• Density tool
– Gamma ray source
– Electrons reflect gamma rays back to detector in tool
– Electrons in formation proportional to density
– Porosity is function of rock type and density
• Sonic tool
– Measures speed of sound in formation
– Porosity slows sound
– Porosity is function of rock type and measured speed of sound

29. GAMMA RAY LOG
• Gamma ray detector measures natural
radioactivity of formation
• Mostly due to Potassium in Shale
– Shale has porosity but no permeability
• Uranium and Thorium
– Less common sources natural radioactivity
– Detected by more sophisticated tools that
measure gamma ray energy
• Run with other tools to correlate logs

30. GAMMA RAY LOG
• Gamma Rays are high-energy electromagnetic waves which are emitted by atomic nuclei as a form
of radiation
• Gamma ray log is measurement of natural radioactivity in formation verses depth.
• It measures the radiation emitting from naturally occurring U, Th, and K.
• It is also known as shale log.
• GR log reflects shale or clay content.
• Clean formations have low radioactivity level.
• Correlation between wells,
• Determination of bed boundaries,
• Evaluation of shale content within a formation,
• Mineral analysis,
• Depth control for log tie-ins, side-wall coring, or perforating.
• Particularly useful for defining shale beds when the sp is featureless
• GR log can be run in both open and cased hole

31. Spontaneous Potential Log (SP)
• The spontaneous potential (SP) curve records
the naturally occurring electrical potential
(voltage) produced by the interaction of
formation connate water, conductive drilling
fluid, and shale
• The SP curve reflects a difference in the
electrical potential between a movable
electrode in the borehole and a fixed reference
electrode at the surface
• Though the SP is used primarily as a lithology
indicator and as a correlation tool, it has other
uses as well:
– permeability indicator,
– shale volume indicator
– porosity indicator, and
– measurement of Rw (hence formation
water salinity).

32. Neutron Logging
• The Neutron Log is primarily used to evaluate
formation porosity, but the fact that it is really
just a hydrogen detector should always be kept
in mind
• It is used to detect gas in certain situations,
exploiting the lower hydrogen density, or
hydrogen index
• The Neutron Log can be summarized as the
continuous measurement of the induced
radiation produced by the bombardment of that
formation with a neutron source contained in
the logging tool which sources emit fast
neutrons that are eventually slowed by
collisions with hydrogen atoms until they are
captured (think of a billiard ball metaphor where
the similar size of the particles is a factor). The
capture results in the emission of a secondary
gamma ray; some tools, especially older ones,
detect the capture gamma ray (neutron-gamma
log). Other tools detect intermediate
(epithermal) neutrons or slow (thermal)
neutrons (both referred to as neutron-neutron
logs). Modern neutron tools most commonly
count thermal neutrons with an He-3 type
detector.

33. The Density Log
• The formation density log is a porosity log that measures electron
density of a formation
• Dense formations absorb many gamma rays, while low-density
formations absorb fewer. Thus, high-count rates at the detectors indicate
low-density formations, whereas low count rates at the detectors indicate
high-density formations.
• Therefore, scattered gamma rays reaching the detector is an indication
of formation Density.
Scale and units:
The most frequently used scales are a range of 2.0 to 3.0 gm/cc or 1.95
to 2.95 gm/cc across two tracks.
A density derived porosity curve is sometimes present in tracks #2 and
#3 along with the bulk density (rb) and correction (Dr) curves. Track #1
contains a gamma ray log and caliper.

34. RESISTVITY LOGS
• Measure bulk resistivity of formation
• Laterlog
– The original well log
– Electrodes direct current into formation to ground
electrodes on surface
• Induction
– Magnetic field induces current in formation
– Used with low conductivity well fluids
• Porosity can be calculated if water salinity is
known
• Oil or gas saturation can be calculated if porosity
and water salinity are known

35. Resistivity Log
• Basics about the Resistivity:
• Resistivity measures the electric properties of the formation,
• Resistivity is measured as, R in W per m,
• Resistivity is the inverse of conductivity,
• The ability to conduct electric current depends upon:
• The Volume of water,
• The Temperature of the formation,
• The Salinity of the formation
The Resistivity Log:
Resistivity logs measure the ability of rocks to
conduct electrical current and are scaled in units of
ohm-
meters.
The Usage:
Resistivity logs are electric logs which are used
to:
Determine Hydrocarbon versus Water-bearing zones,
Indicate Permeable zones,
Determine Resisitivity Porosity.

36. Prof. Dr. H. Z. Harraz
• Acoustic tools measure the speed of sound waves in
subsurface formations. While the acoustic log can be
used to determine porosity in consolidated formations, it
is also valuable in other applications, such as:
• Indicating lithology (using the ratio of compressional
velocity over shear velocity),
• Determining integrated travel time (an important tool for
seismic/wellbore correlation),
• Correlation with other wells
• Detecting fractures and evaluating secondary porosity,
• Evaluating cement bonds between casing, and formation,
• Detecting over-pressure,
• Determining mechanical properties (in combination with
the density log), and
• Determining acoustic impedance (in combination with
the density log).
Acoustic Log

37. DIP METER AND BOREHOLE IMAGING
• Dip Meter
– Four or six arms with few buttons measure small scale resistivity
– Wellbore inclination and orientation
– Map bedding planes of sedimentary formations
• Imaging Tools
– Resistivity imaging tools
• FMI - Schlumberger, EMI – Halliburton
• Pads with many buttons map small scale resistivity
– Ultrasonic imaging tools
• USIT – Schlumberger, CAST – Halliburton
• Spinning ultrasonic transducer measures I.D. and sonic impedance
– Borehole image
• Dip and orientation of fractures
• Structure and stress of formation
– Borehole breakout
– Drilling induced fractures

38. OTHER GEOPHYSICAL
LOGS
• Mineral identification
– Pulsed neutron source stimulates gamma ray
emissions
– Tool measures energy spectrum of returning
gamma rays
– Percentage of elements (silica, calcium, etc.)
• Magnetic resonance
– Detects free water
– Determine permeability

39. GEOTHERMAL APPLICATIONS
• Geophysical tools designed for sedimentary
formations
– Algorithms for sandstone, shale, limestone, dolomite
– Special algorithms required for crystalline rock
• Resistivity tool is sufficient to quantify porosity when
water salinity is known
• Sonic tool puts seismic surveys on depth
• Density tool calibrates gravity surveys
• Formation imaging tools map fractures and quantify
stress regime
• Neutron and density tools can identify lithology,
– if samples are available to create correlations
– if there is variation in rock type

42. Schlumberger Litho-Density Log

43. PRODUCTION LOGS
• Very useful in geothermal wells
• Can be run with simple or sophisticated
equipment
• Temperature surveys are essential for
exploration work
• Pressure & Temperature surveys are
more useful for well testing and
production

44. TEMPERATURE LOGS
• Most important parameter in geothermal wells
• Thermocouple wire
– easiest for shallow holes
• RTD
– most accurate
• Mechanical tool
– Only option for deep hot wells 10 years ago
• Electronic surface readout tool in thermal flask
– Requires high temperature wireline
• Electronic memory tool in thermal flask
– State of the art
– Slick line or braided cable
• Fiber Optics
– Instantaneous temperature profile of entire wellbore
– Good for measuring transients
• High temperature electronics
– Not yet commercial

46. TEMPERATURE PROFILE
TEMPERATURE
DEPTH
SURFACE
CONDUCTIVE GRADIENT
HYDROTHERMAL SYSTEM
UPFLOW
CONDUCTIVE HEAT SOU
OUTFLOW ZONE
TEMPERATURE
REVERSAL

47. PRESSURE LOG
• Second most important reservoir parameter
– pressure drives flow
– producing drawdown indicates reservoir productivity (or injection buildup)
– drawdown curves analyzed to determine reservoir permeability
• Water level, easily measured
– used in hydrology but less useful in geothermal systems
– dependant on wellbore temperature and gas or steam pressure above water
• Mechanical pressure tool
– common ten years ago
• Capillary tubing filled with nitrogen or helium
– reservoir pressure is measured at surface
– good for long term reservoir pressure monitoring of hot wells
• Electronic surface readout tool in thermal flask
– requires high temperature wireline
• Electronic memory tool in thermal flask
– state of the art
– slick line or braided cable

48. STATIC PRESSURE AND TEMPERATURE PROFILES
0
200
400
600
800
1000
1200
0 50 100 150 200 250 300 350
PRESSURE TEMPERATURE
DEPTH
STATIC PRESSURE STATIC TEMPERATURE
WATER LEVEL

49. STATIC AND FLOWING PRESSURE AND TEMPERATURE PROFILES
0
200
400
600
800
1000
1200
0 50 100 150 200 250 300 350
PRESSURE TEMPERATURE
DEPTH
STATIC PRESSURE
FLOWING PRESSURE
STATIC
TEMPERATURE
FLOWING
TEMPERATURE
PRESSURE DRAWDOWN
FLASH DEPTH
FLASH DEPTH

50. SPINNER LOG
• Propeller measures flow in wellbore
• Identifies production (or injection) zones
• Calculate fluid velocity from series of up
and down runs at different cable speeds

51. FLOWING SPINNER SURVEY
0
200
400
600
800
1000
1200
-10 0 10 20 30 40 50
SPINNER COUNTS
DEPTH
Log down 100 fpm Log up 100 fpm
MAIN PRODUCTION ZONE
FLASH DEPTH

52. TYPICAL SHALLOW WELL LOGGING UNIT
From USGS website, nc.water.usgs.gov

53. TYPICAL SLICK LINE WINCH
From BOP Controls Inc. website, bopcontrols.net

54. WELL INSPECTION LOGS
• Sonic Cement Bond Log (Same tool as sonic porosity log)
– Measures quality of cement on outside of casing
– Difficulty with large geothermal well casing
– Difficulty with micro-annulus caused by temperature and pressure changes
• Caliper
– Measures I.D. of casing
– Detects corrosion, scale, washouts, parted casing
• Electro-magnetic
– Measures metal loss
– Detects corrosion, holes and parted casing
• Ultrasonic (same as imaging tool)
– Measures I.D. and thickness of casing, and impedance of material behind casing
– Detects corrosion, holes and cement
• RA Tracer
– Injects slug of iodine 131 into wellbore
– Gamma ray detector measures radioactive slug
– Detects leaks in casing and flow behind pipe
• Video
– Identify well problems
– Requires very clear water

55. PRESSURE CONTROL
Should be used there is any possibility of well flowing
Pack-off
– Rubber cylinder tightens around wireline
– Few hundred psi
Lubricator
– Length of pipe below pack-off
– Necessary to run tool in pressurized well
Blow out preventor
– Valve below lubricator that closes around
wireline
– Useful if pack-off fails or wireline gets stuck in
pack-off
Grease tubes for high pressure
– Placed below pack-off
– For thousands of psi
– Grease pumped in high pressure end flows to
low pressure
Grease in
High pressure
Grease out
Low pressure

56. PRESSURE-TEMPERATURE-
SPINNER TOOLS FOR SALE
• MADDEN SYSTEMS (Odessa, TX)
– Flasked surface readout and memory tools
• KUSTER COMPANY (Long Beach, CA)
– Mechanical tools
– Flasked surface readout and memory tools
Anyone with a slickline or braided cable
winch can run memory tools.

57. GEOPHYSICAL LOGGING TOOLS
AND WIRELINE WINCHES FOR
SALE
• Companies that used to make tools and
sell wireline systems went out of
business in the 1990’s
• Companies that sell systems now are
on the internet

59. The Big Three
• SCHLUMBERGER
• HALLIBURTON
• BAKER ATLAS
Worldwide Geophysical, Production
& Inspection Logging
Video
• DOWNHOLE VIDEO – Oxnard
CA
• many other companies
Geothermal Production Logging
• WELACO – Bakersfield CA
• PACIFIC PROCESS SYSTEMS –
Bakersfield CA
• SCIENTIFIC PRODUCTION
SERVICES – Houston TX
• INSTRUMENT SERVICES INC. –
Ventura CA
Pressure-Temperature-Spinner
& some other services
Sell and service equipment
Many other companies in Japan, New
Zealand, Philippines, Iceland,
Kenya (KenGen), etc.
COMMERCIAL BOREHOLE
LOGGING COMPANIES

60. 1- Formation Evaluation
A- Virgin Reservoir
(Mainly Open Hole Logs)
B-Developed & Depleted Reservoirs
(Mainly Cased Hole Logs)
2- Monitoring Reservoir Performance
Reservoir Performance Problems
Well Performance Problems
Reservoir Description

63. Some Well Mechanical Problems

65. Important Questions
Is the Well Producing at Its Potential?
If It Is Not , Why Isn’t It?
What is the Well Production Potential?
Is It: the Well Production on Well Test
OR
Is It: What Well Is Capable to Produce

66. Causes of Low / Production Disturbance
A- Non- Treatable Problems
1- Low Formation KH
2- Poor Relative permeability
3- High GOR or WOR
4- High Viscosity
B- Treatable Problems
1- Formation Problems
( Organic & Inorganic Precipitates, Stimulation
Fluids, Clay Swelling, Mud Effects)
2- Production Equipments Problems
( Cement & casing, Tubing, Artificial Lifts)

67. It is fine to Understand Types of
Problems and Their Causes.
But It Is More Important To Determine
That A Problem Does Exist.
Diagnosis of Causes
A- Surface Data Analysis
B- Drilling Report
C- Workover, Completion and
Stimulation Data

68. Well Log Classification
Overview

69. Well Log Classification and
Cataloging
Industry Data
Company Data
Well Log Catalog
Well Log Data Repository PWLS Class Repository

70. Activities Enabled by PWLS
Meta Data
• Classify well logs
• Classify well log channels
• Query for well logs
• Query for well log channels

71. Classify a Well Log / Channel
/ Parameter
• well log  well_log_service_class
– by interpretation of well log header
• channel  company_channel_class
– validate against dictionary
• parameter  company parameter spec.
– validate against dictionary

72. Genericity of classification
• original acquired data  primarily co.
data
– company channel class
– well log service class
• computed data  primarily industry
data
– well log curve class
– well log tool class
• processed data  combined approach

73. Query by technology
• goal: logs of a given technology
• industry classification:well log tool class
• company classification: well log service
class
• catalog: classification by well log
service class
• result: well log data

74. Query by channel attributes
• goal: channels of a given object,
property, function, ...
• industry classification:well log curve
class
• company classification: company
channel class class
• catalog: classification by company
channel class
• result: well log data

75. Query by propery type
• goal: channels of a given property type
• industry classification: well log curve
class
• company classification: company
channel class class
• catalog: classification by company
channel class
• result: well log data

76. Parameter-Augmented Query
• goal: well logs, subject to parameteric
constraints e. g. total_depth > 33000 ft
• industry classification: param spec (property
type) e. g. Bottom_Depth
• company classification: company parm spec
e. g. BOTTOM_DEPTH
• catalog: parametric classification e. g.
BOTTOM_DEPTH=44000(m)
• result: well log data

77. Existing Data
Well Log Catalog
Well Log Data Repository
15:MDL : xxxxxxxxx
150:CDL : xxxxxxxxx
280:SLD : xxxxxxxxx
440:LDS : xxxxxxxxx
Dictionary
query
engine

78. Queries
Well Log Catalog
Well Log Data Repository
15:MDL : xxxxxxxxx
150:CDL : xxxxxxxxx
280:SLD : xxxxxxxxx
440:LDS : xxxxxxxxx
Dictionary
Where are my density logs?

79. Existing Data
Well Log Catalog
Well Log Data Repository
15:MDL : xxxxxxxxx
150:CDL : xxxxxxxxx
280:SLD : xxxxxxxxx
440:LDS : xxxxxxxxx
Dictionary
query
engine
Industry Data
PWLS
Company Data
15:MDL : xxxxxxxxx : Density
150:CDL : xxxxxxxxx : Density
280:SLD : xxxxxxxxx : Density
440:LDS : xxxxxxxxx : Density
Density : xxxxxxxxx
Acoustic : xxxxxxxxx
Neutron : xxxxxxxxx
... density ...
Prof. Dr. H. Z. Harraz

80. Textbook & References
Textbook:
1- Hill, A.D., 1990," Production Logging- Theoretical and
Interpretive Elements", SPE Series, vol.14.
2- Instructor Notes: Production Logging & Cased–Hole Logging
in Vertical and Horizontal Wells).
References:
1- Schlumberger, 1987," Cased- Hole Log Interpretation:
Principles / Applications", Schlumberger Ltd., Houston.
2- Rollins, D.R., et al, 1995," Measurement While Drilling", SPE
Series vol.40.