Basics well logging
(fields Applications(
Abbas Radhi Abbas
‫عباس راضي عباس‬
Iraq 2016
Contents
1. Introduction
 Define of well logging
 Uses of well logging in petroleum engineering
 Who use logs?
 who responsible for well logging?
2. Type of well logging
 Open hole logging
-Conventional logs ( SP , GR , CAL , DLL , MSFL , Density ,
Neutron , sonic)
-High tech logs : ( NMR , FMI , MDT ,SWC , VSP )
 Cased hole logging
- Cement bond log ( CBL and Image log )
- Production logging tools ( PLT )
- Reservior saturation log ( RST )
- casing inspection log ( MIT , MFC)
3. Log interpretation
 interpretation Procedure
 interpretation steps
 Calculation Petrophysical parameters (Vsh , φ , K , SW )
4. Some pictures for logging truck and logging tools
2
1
Contents
1. introduction
2. Type of well logging
3.Log interpretation
4.Some pictures for logging truck and logging tools
3
2
Well Logs :
are measurements
of physical properties of
the rock type ( porosity ,
permeability , volume of
shale , water saturation )
related to depth
by
using ( Resistivity ,
Density , neutron ,
acoustic , SP , GR
properties , etc ).
4
3
2-Uses of well logging in petroleum engineering
1.
2.
3.
4.
5.
6.
7.
8.
9.
5
Rock typing
Identification of geological environment
Reservoir fluid contact location
Fracture detection
Estimate of hydrocarbon in place
Estimate of recoverable hydrocarbon
Determination of water salinity
Reservoir pressure determination
Porosity/pore size distribution
determination
4
Many Engineers use logging depend
his requirements :
1.
2.
3.
4.
5.
6.
7.
6
Geologist
Geophysics
Petrophysics Engineer
Reservoir Engineer
Drilling Engineer
Workover Engineer
Completion Engineer
5
Petrophysics Engineer
responsible for all logging :
1.
design types of logging ( open Hole
and cased Hole ) in vertical and
directional wells .
2. Supervision during run logging tools
in well site
3. Check all Quality of logging in well
site
4. Do log interpretation by using
interpretation software
7
6
Contents
1. introduction
2. Type of well logging
3.Log interpretation
4.Some pictures for logging truck and logging tools
8
7
Vertical well
Horizontal well
nI ofm
r atoin
Management,
DrilnigEngnieernig,
DaatMudolggnig,
Rgi-SiteSupervsioin
DrilnigDynamcis
DrilnigFul diSysetms
High Tech
logs
Conventional
logs
Fom
r atoin
EvaulatoinMWD
Hgih
Perofm
r anceBits
Seterabel
Drilnig
Systems
9
8
Conventional logs
1. Lithology logs :
 SP
 GR
2. Porosity logs :
 Density
 Neutron
 Sonic
High tech logs
Cased Hole logging
1. Nuclear magnetic
resonance log (NMR)
2. Modular formation
dynamic tester (MDT)
3. Micro resistivity
Imaging
4.Sidewall core
5. Vertical seismic
profile (VSP)
1. Cement evaluation
log :
(A) normal CBL , VDL ,
GR , CCL
(B) Image cement
evaluation
 SBT
 URS
 CBMT
2. production logging
tools ( PLT)
3. Oil saturation log
4. Casing inspection log
3. Resistivity logs :
 Resistivity
 Induction
4. Caliper log
10
9
Open Hole logging
Vertical well
Horizontal well
Information
Management,
DrillingEngineering,
DataMudlogging,
Rig-SiteSupervision
DrillingDynamics
DrillingFluidSystems
Formation
EvaluationMWD
High Tech
logs
11
Convention
al logs
10
High
PerformanceBits
Steerable
Drilling
Systems
Conventional
logs
1. Lithology logs :
 SP
 GR
2. Porosity logs :
 Density
 Neutron
 Sonic
3. Resistivity logs :
 Resistivity
 Induction
4. Caliper log
12
11
-100
SP
0
100
5185
5195
Useful for:
5205
 Detecting
Shale
5215
permeable beds
and it thickness.
5225
5235
5245
5255
 Determining
Sandstone
5265
formation water
salinity .
5275
5285
5295
 Qualitative
Shale
5305
indication of bed
shaliness.
5315
5325
5335
5345
Sandstone
5355
5365
5375
5385
5395
5405
5415
13
12
Shale
GAMMA RAY LOG (GR)
-100
•
•
•
•
•
•
Gamma ray log is
measurement of natural
radioactivity in formation
5185
It measures the
radiation emitting from
naturally occurring U,
Th, and K.
5225
GR log is indictor for
shale
Correlation between
wells,
0
GR
100 200
5195
5205
5215
Shale
5235
5245
5255
5265
Sandstone
5275
5285
5295
5305
Shale
5315
5325
Depth control for log all
logs and perforation
5335
GR log can be run in
both open and cased
hole
5365
5345
5355
5375
Sandstone
5385
5395
5405
5415
14
13
Shale
Correlation between wells by GR
15
14
SP , GR , CAL -Log
16
15
The acoustic/sonic log
is a porosity log that
measures the interval
transit time of a
compressional wave
traveling through one
foot of formation. The
logging sonde consists
of one or more
transmitters, and two
or more receivers.
Modern acoustic/sonic
logs are borehole
compensated devices.
17
16
The formation density log is
a porosity log that measures
the electron density of the
formation. The density
logging tool consists of a
radioactive source that
emits gamma rays into the
formation and one or more
gamma ray detectors,
located a fixed distance from
the source.
‫وهذا المجس يقيس كثافة الصخور والتي لها عالقة عكسية مع المسامية اذا كلما‬
‫ازدادت المسامية كلما قلت الكثافة ويعتبر االنهيدرايت من اكثر الصخور كثافة اما‬
. ‫اقلها كثافة فهي الحجر الكلسي المسامي والدلومايت ذو الفجوات‬
18
17
‫‪Neutron logs are‬‬
‫‪porosity logs that‬‬
‫‪essentially measures‬‬
‫‪the hydrogen‬‬
‫‪concentration in a‬‬
‫”‪formation. In “clean‬‬
‫‪formations, where the‬‬
‫‪pore spaces are filled‬‬
‫‪with water or oil, the‬‬
‫‪neutron log measures‬‬
‫‪liquid-filled porosity.‬‬
‫وهذا المجس يقيس المسامية ايضا ولكن بصورة غير مباشرة اذا انه يقيس عدد ذرات‬
‫الهيدروجين في الصخرة والتي لها عالقة بالمسامية عن طريق مصدر سيل من النيوترونات‬
‫التي تصطدم بالهيروجين الموجود في الصخرة وكل ذرة هيدروجين موجودة في الصخرة‬
‫تؤدي الى اصطياد نيوترون يصطدم بها وهكذا من معرفة عــدد النيوترونات التي اصطيدت‬
‫نستطيع تقديــر عدد ذرات الهيدروجين في الصخرة وبالتالي المسامية لتلك الصخرة ‪.‬‬
‫‪18‬‬
‫‪19‬‬
20
19
Lithology Using Porosity Log Combinations
21
20
Lithology Using Neutron-density cross plot
Cross plot of Neutron-Density
-Sandstone)
22
21
cross plot of Neutron-Density
Limestone)
Density and neutron behavior
23
22

Use to measure the resistivity of
the formation, and thus the
possibility of hydrocarbon shows.

Many types of resistivity log use ,
but the famuse are ( MSFL , DLL)
DLL : Dual Laterolog Resistivity( long “ RD”
, short “ RS” )
MSFL : Micro Spherical Focused Laterolog
24
23
MSFL
1.
•
•
High resistivity mean:
Hydrocarbon
Tight zone ( low porosity
)
2. Low resistivity mean:
• Shale
• water
3. Separation between
resistivites mean
• Formation fluid is
different from drilling
fluid .
SFL
Formation Fluid
different from
Drilling Fluid
Formation Fluid
similar to
Drilling Fluid
25
24
26
25
Induction logs are used in
wells that do not use water or
mud, but oil-based drilling
fluids or air. They are nonconductive
and
therefore
cannot use electric logs
instead they use magnetism
and electricity to measure
resistivity.
27
26
Rm – resistivity of the drilling mud
Rmc – resistivity of the mud cake
Rmf – resistivity of mud filtrate
Rs – resistivity of shale
Rt – resistivity of uninvited zone(true
resistivity)
Rw – resistivity of formation water
Rxo – resistivity of flushed zone
28
27
Caliper Log
1-A caliper log is a well logging tool that provides a
continuous measurement of the size and shape of a
borehole along its depth The measurements that are
recorded can be an important indicator of caving
2- this log use by cementing engineer to calculate the
volume of cement .
29
28
30
29
A caliper log in horizontal
well can not get it by wire
line because wireline can
cover to about 60 degree
, after 60 degree can use
another tools by LWD
called ultra sonic caliper ,
this tools can give caliper
log 2D and 3D
31
30
ultra sonic caliper , Example : this tools can give
caliper log 2D and 3D
32
31
33
32
Classification of the wells
Well types
Drilling
purpose
-
Exploration
well
Appraisal
well
Developmen
t well (
-
producer ,
water
injection well)
34
Drilling
depth
-
-
short depth
Medium
depth
Deeper
33
Well
trajectory
- Vertical
well
- Directional
well
Example :wire line logging program
( in vertical wells)
No.
1
Interval
17-1/2"
（OH）
13.375”(CH)
2
12-1/4"
（OH）
9.625”(CH)
8-1/4"（OH）
Depth(m)
120-2287
0-2287
2287-2893.8
-2893.8
2893.8-3208
Logging items
1) DLL*/MSFL/DT/GR/SP/CAL
1)CBMT/VDL/CCL/GR
1) DLL*/MSFL/DT/GR/SP/CAL
1)CBMT/VDL/CCL/GR
1) DLL*/MSFL/XDT/DEN/CNC/GR /SP/CAL
3
6.625”(CH)
35
-3208
1)CBMT/VDL/CCL/GR
34
DLL : Dual Laterolog Resistivity
MSFL : Micro Spherical Focused Laterolog
DT
: Digital sonic
GR
: Gamma Ray
SP
: spontaneous potential log
CAL : Caliper Log
CBMT : Cement Bond Imaging log
VDL : Variable Density log
CCL : casing-collar locator
XDT : Cross Dipole Sonic
DEN : Density Log
CNC : Compensated Neutron log
36
35
Run(1): GR/SP/CAL/DLL/MSFL/XDT
Run(2): GR/DEN / CNS
37
36
Depth of investigation of logging tools
38
37
Common logs and what they measure
39
38
Open Hole logging
Vertical well
Horizontal well
Information
Management,
DrillingEngineering,
DataMudlogging,
Rig-SiteSupervision
DrillingDynamics
DrillingFluidSystems
Formation
EvaluationMWD
High Tech
logs
40
Convention
al logs
39
High
PerformanceBits
Steerable
Drilling
Systems
1. Nuclear magnetic resonance log (NMR)
2. Modular formation dynamic tester (MDT)
3. Micro resistivity Imaging (FMI)
4.Sidewall core (SWC)
5. Vertical seismic profile (VSP)
41
40
Application
-Effective Porosity
- Capillary Bound Water
- Free Fluid
- Clay Bound Water
- Total Porosity
42
41
43
42
Micro Resistivity imaging log (FMI)
Application





44
Fracture identification and characterization
Thin-bed analysis
Characterization of sedimentary bodies
Structural analysis
Secondary porosity evaluation
43
Example :Micro Resistivity imaging log
In this interval XRMI
fractures are fitted
with coring fractures
45
44
MDT ( Modular formation dynamic tester)
46
45
MDT
• MDT:Modular Dynamic Formation Tester is the
tool through which we can test the
formation and measure the formation
pressure, temperature and get the pure
reservoir fluid and water samples.
Many name of this tools depend of
companies (MDT, RFT RDT, RCI)
Application
1.
2.
3.
4.
47
Identify the pressure test
Identify the permeability
Identify the fluid contact (OWC)
Identify fluid type (Oil or Water)
46
MDT System
48
47
MDT Tool
49
48
MDT Technique
50
49
MDT Job Planning
MDT job is designed after evaluating the open
hole logs. There are few main points which
should be keep in mind before planning the
job.
1. Select the depth points for formation pressure.
2. Select at least three (3) pressure points in one bed.
3. Pressure points should fall in oil/gas zones and
water bearing zone.
4. Select the oil/gas sample point, which should be
clean and try to get it from top of the reservoir.
5. Also select a point for water sample in water
bearing zone.
6. MDT oil/gas sample is very suitable for PVT analysis.
51
50
MDT INTERPRETATION
Interpretation of MDT data is very interesting.
For interpretation you have to make a graph
between the formation pressure and depth.
When you plot the formation pressure against
the depth you will get the density gradient,
values of which are given as under:
Oil, Gas and Water has different gradients.
1-Gas = 0.55 g/cc
2-Oil = 0.88 g/cc
3-Water = 1.0 g/cc
52
51
Density calculation by MDT
53
52
Identify OWC by MDT
MDT
54
53
Identify Fluid Type by MDT
55
54
56
55
57
56
Rotary Sidewall Coring system
58
57
59
58
60
59
Core analysis can be divided into two
types:
1. Conventional core analysis .
2. Special core analysis .
1. Conventional core analysis .
Provide information about lithology ,
residual fluid saturation , porosity and
permeability .
61
60
2. Special core analysis .
•
•
•
•
•
•
62
Porosity and permeability at elevated
confining stress .
Electrical properties such as formation
factor and. resistivity index .
Capillary pressure.
Wettability and relative permeability.
Mechanical rock properties such as
compressibility.
Water food sensitivity for infectivity
and well performance.
61
Drilling coring
SWC
Advantage:
Advantage:
the core is regular,
cylindrical and little formation
pollution.
Easy, fast ,Low cost.
The core can be used for
many different analysis.
Disadvantage:
Disadvantage:
High cost
In the most case the core is
irregularly ,small and destroyed.
Complex
 The explosive device must be
used in SWC operation, which is
dangerous.
Affecting drilling speed
Low recovery rate, Especially
in hard formation.
63
62
VSP : Vertical seismic profiles, as the name
suggests, are run vertically in a wellbore to
obtain detailed seismic response near the
wellbore. After correcting for the very
different geometry of such a survey, the
results are presented in seismic section
format. They can be correlated with
conventional seismic data and with synthetic
seismograms made from the sonic and
density logs in the same wellbore.
64
63
Open Hole logging
Vertical well
High Tech
logs
65
Convention
al logs
64
Horizontal well
Information
Management,
Drilling Engineering,
Data Mudlogging,
Rig-Site Supervision
Drilling Dynamics
Drilling Fluid Systems
Formation
Evaluation MWD
High
Performance Bits
Steerable
Drilling
Systems
66
65
Logging design and procedure
67
66
Logging design and procedure
68
67
69
68
Some available measurement in LWD
technology
1. Gamma Ray
2. Resistivity
3. One porosity log (Density & neutron & sonic)
4. Borehole caliper (Ultra sonic azimuthal caliper)
Information
Management,
DrillingEngineering,
DataMudlogging,
Rig-SiteSupervision
DrillingDynamics
DrillingFluidSystems
Formation
EvaluationMWD
High
PerformanceBits
Steerable
Drilling
Systems
70
69
The following is a list of available
measurement in LWD:
1-Natural gamma ray
2-Spectral gamma ray
3-Azimuthal gamma ray
4-Gamma ray close to drill
bit.
5-Density and photoelectric
index
6-Neutron porosity
7-Borehole caliper
8-Ultra sonic azimuthal
caliper
9-Density caliper
10-Attenuation and phase
shift
resistivities at different
transmitter
11-spacings and frequencies
71
12-Resistivity at the drill
bit
13-Deep directional
resistivities
14-Compressional
slowness
15-Shear slowness
16-Density borehole
images
17-Resistivity borehole
images
18-Formation tester and
sampler
19-Formation pressure
20-Nuclear magnetic
resonance
21-Seismic while drilling
22-Vertical seismic
profile
70
72
71
73
72
GR & Resistivity distance from bit
74
73
Example : LWD for SLB
LWD procedure :
1. Real time ( GR ,
Resistivity )
2. Porosity trip log (one
porosity log )/ GR,
sonic or neutron)
75
74
Vertical well
Horizontal well
nI ofm
r atoin
Management,
DrilnigEngnieernig,
DaatMudolggnig,
Rgi-SiteSupervsioin
DrilnigDynamcis
DrilnigFul diSysetms
High Tech
logs
Conventional
logs
Fom
r atoin
EvaulatoinMWD
Hgih
Perofm
r anceBits
Seterabel
Drilnig
Systems
76
75
77
76
(2)Cased Hole logging
Cement evaluation log :
(A) normal CBL , VDL , GR
, CCL
(B) Image cement
evaluation
SBT ,URS ,CBMT
1
2
production logging tools ( PLT)
Cased
Hole
logging
reservoir saturation
3
log (RST)
4
78
Casing inspection
log (MIT)
77
Cement Bond Log (CBL &CBMT)
79
78
Three types for cement log run in missan oil
bellow table: fields , see
No
80
LOG
Long name
Casing
size
Company
1
CBL Cement Bond Log 13-3/8”
BHDC , COSL ,
WFD
2
CBM
T
9- 5/8”
6-5/8”
BHDC , COSL
3
URS Ultra sonic redial
scanner
9- 5/8”
6-5/8”
WFD
Cement Bond
Image Tool
79
13-3/8” CBL , VDL , GR , CCL
Evaluation Criterion:
• V.Good Cement CBL≤5%
• Good Cement 5%< CBL≤15%;
• Medium Cement 15%< CBL≤25%
• Poor Cement CBL>25%.
81
80
(CBL) Cases
82
81
Cement Bond Image Log (CBMT)
Evaluation Criterion: depend on ( ATAV)
Free pipe ( 0 to≤ 2) db/ft
· Poor cement (>2 to≤ 6) db/ft
· Medium cement (>6 to≤10)db/ft
· Good cement (>10 to≤12) db/ft
· Very Good cement (>12 to 20) db/ft
83
82
Example : (CBMT)
Attenuation
Array
Variable
Attenuat
ion Map
VDL
Variable
Density
Log
Casing wave
Bad cement
Medium cement
Bad cement
Medium cement
Bad cement
Very Good cement
Formation
wave
84
83
Ultra sonic redial scanner(URS)
Evaluation Criteria: depend on IMPD
•
•
•
•
•
•
85
( IMPd<=0.38,"gas“
( IMPd>0.38, IMPd<=2.3),"liquid gas-Fresh Wtr",
( IMPd>2.3, IMPd<=2.7),"Heavy drill fluid",
( IMPd>2.7, IMPd<=3.85),"low IMPd",
( IMPd>3.8, IMPd<=5),"medium IMPd",
( IMPd>5),"good IMPd")
84
Production Logging Tools -PLT
86
85
Production Profile Log
Purpose
a. Calculate water, oil and gas rate of each pay zone.
b. Judge whether the sliding sleeve shuts or not and
estimate which zone is primary water production layer.
c. Determine gas production zone.
d. Make sure the fluid level and production pressure by
measuring whole interval.
e. Make sure whether there is crossflow in the shut-in
state.
Three-phase flow
87
86
Shut-in
Production Profile
Log
Production profile logging ：
Obtain the variation of the
flow rate in each perforation,
water production intervals
and gas inlets etc, thus
providing basis for taking
stimulation treatments.
Injection profile logging ：
Obtain the movement of the
inject fluid or gas, the
absorption quantity in each
perforation and analysis of
injection-production relation.
88
87
Production Profile Log
89
88
PLT-Quantitative interpretation
90
89
PLT-Quantitative interpretation
91
90
PLT-Quantitative interpretation
92
91
PLT-Tool introduction






Flowmeter
 Continuous spinner
flowmeter
 Fullbore spinner flowmeter
 Basket spinner flowmeter
Radioactivity fluid density
Water hold-up
Temperature and Pressure
Spontaneous Gamma ray and
Cased Collar Located
Caliper, Electromotion
Centralizer and so on
Surface Read-Out Production Logging
Memory Production Logging
93
92
PLT-Quality control
GR: Repeat measurements curves have similar shape, and the
curves are consistent with the original gamma curves
CCL: Curves change significantly, downhole tools such as sleeves
and packers have obvious characteristics.
Spinner: Good correlation, stability logging speed and no cross
and abnormal.
Density: Good repeatability, curves change significantly around
the interface of oil and water, gas and water, oil and gas and the
gas outlet orifice.
Capacitance: Curves change stable in the zero-flow interval, in
the oil-water interface, gas-water interface have significant
changes.
Pressure: Good repeatability, no significant abnormality.
Temperature: Have significantly change in the liquid outlet
orifice, shut-in curves have the same trend with the temperature
curves when the well is produce
.
94
93
PLT-Qualitative analysis
spinn
er
Flowmeter
second
Main production zone:
flowmeter curves change
great
main
The greater the
flowmeter curves
change, the more liquid
it produces or absorbs.
third
95
94
PLT-Qualitative analysis
Density &
Capacitance
Oil & Gas:
Density decrease and
capacitance increase
Water:
Density increase and
capacitance decrease
96
95
Example for PLT
Perforation interval
Interpretation interval
Zone
A
Oil
B/D
B/D
5.8
409.2
Contributions by phase
Top m
Bottom m
2972.0
2993.0
3016.0
2984.0
2996.0
3019.0
3045.0
3055.0
3045.0
3055.0
462.0
322.5
784.5B/D
3083.0
3066.0
3072.4
3079.9
3069.9
3077.0
3083.0
3.0
43.1
495.3
89.1
197.9
1697.6
92.1B/D
241.0B/D
2192.9B/D
B
3065.0
97
Water
Top m
Bottom m
SSD
0.0
2000.0
4000.0
415.0B/D
Water
96
OIL
Prepare PLT-tools in well site
98
97
reservoir saturation log (RST)
the reservoir saturation log (RST) makes both
formation sigma and C/O ratio measurements that
allow the calculation of water saturation without the
need for a resistivity log..
99
98
reservoir saturation log (RST)
Reservoir saturation tools such as the pulsed
neutron (TDT) are still widely used. the reservoir
saturation log (RST) makes both formation sigma
and C/O ratio measurements that allow the
calculation of water saturation without the need
for a resistivity log..
In formations with high-salinity formation water, the
sigma measurement has been used for several decades
to determine water saturation. The C/O ratio
measurement can accurately evaluate water saturation
in moderate to high porosity formations regardless of
water salinity. This calculation is particularly helpful if
the water salinity is low or unknown. If the salinity of
the formation water is high, the Dual-Burst Thermal
Decay
100
99
Reservoir saturation log (RST)
Time measurement is used. A combination
of both measurements can be used to
detect and quantify the presence of
injection water of a different salinity from
that of the connate water.
Time-lapse measurements of water
saturation can be used to monitor the
performance of a well or reservoir over
time. TDT logs have gone throufg many
evolutionary changes over the years so
reservoir monitoring is difficult, especial;;y
in low porosity reservoirs. Some age related
normalization and bore hole corrections are
often needed to makes sense of the data.
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100
Application of RST
1.
2.
3.
4.
5.
6.
7.
8.
9.
102
Formation evaluation behind casing
Sigma, porosity, and C/O measurement in one trip in
the wellbore
Water saturation evaluation in old wells where
modern open hole logs have not been run
Measurement of water velocity inside casing,
irrespective of wellbore angle (production logging)
Measurement of near-wellbore water velocity
outside the casing (remedial applications)
Formation oil volume from C/O ratio, independent
of formation water salinity
Capture yields (H, Cl, Ca, Si, Fe, S, Gd, and Mg)
Inelastic yields (C, O, Si, Ca, and Fe)
Borehole salinity
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Casing inspection log
(MIT)
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102
Casing insertion log (MIT)
MIT= multi – Finger imaging tool
(24 , 40 ,60 ) finger
Applications
• Monitoring internal casing corrosion
or scale buildup
• Evaluation of drilling wear
• Identification of split, parted, or
deformed casing
• Evaluation of deformation caused by
geomechanical factors
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103
Example :Casing insertion log (MIT)
105
104
Contents
1. introduction
2. Type of well logging
3.Log interpretation
4.Some pictures for logging truck and logging tools
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105
(3) Log interpretation
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106
Petrophysical Interpretation
Qualitative: Assessment of
reservoir properties, fluid type
form log pattern.
Quantitative: Numerical
estimation of reservoir
properties of oil, water etc.
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107
Qualitative interpretation of well logging
•
Estimation of effective porosity & permeability.
•
Estimation of volume of shale.
•
Estimation of hydrocarbon saturation.
•
Determination of the depth and thickness of net pay
•
Estimation of reserves of hydrocarbon.
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108
interpretation Procedure
The basic logs, which are required for the
adequate formation evaluation, are:
1. Permeable zone logs (SP, GR, Caliper)
2. Resistivity logs (MFSL, Shallow and Deep
resistivity logs),DLL
3. Porosity logs (Density, Neutron and Sonic).
Generally, the permeable zone logs are presented in
track one, the resistivity logs are run in
track two and porosity logs on track three.
Using such a set of logs, a log interpreter has to
solve the following problems,
(I). Where are the potential producing hydrocarbons
zones?
(II). How much hydrocarbons (oil or gas) do they
contain?
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interpretation steps
First step: The first step in the log interpretation is to locate
the permeable zones. Scanning the log in track one and it has
a base line on the right, which is called the shale base line.
This baseline indicates shale i.e., impermeable zones and
swings to the left indicate clean zones- e.g., sand, limestone
etc. The interpreter focuses his attention immediately on
these permeable zones.
Next step: To scan the resistivity logs in track 2 to see which
of the zones of interest gives high resistivity readings. High
resistivities reflect either hydrocarbons in the pores or low
porosity.
Next step: Scan the porosity logs on the track 3 to see which
of the zones have good porosity against the high resistivity
zones. Discard the tight formations. Select the interesting
zones for the formation evaluation
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110
Petrophysical parameters
Petrophysical parameters
determined From logs :
1.Vol. of shale (Vsh)
2.Porosity (φ) .
3.Permeability (K).
4.Water saturation (SW)
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111
Porosity:
Is the percentage of voids to the
total volume of rock. It is measured as a percent
and has the symbol
The amount of internal space or voids in a given
volume of rock is measure of the amount of
fluids a rock will hold. The amount of void space
that is interconnected, and so able to transmit
fluids, is called effective porosity. Isolated pores
and pore volume occupied by adsorbed water
are excluded from a definition of effective
porosity.
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112
Permeability: Is the property a rock has to transmit
fluids. It is related to porosity but is not always
dependent upon it. Permeability is controlled by the
size of the connecting passages (pore throats or
capillaries) between pores. It is measured in darcies or
millidarcies
absolute permeability : the ability of a rock to transmit
a single fluid when it is 100% saturated with that fluid
Effective permeability : refers to the presence of two
fluids in a rock, and is the ability of the rock to transmit
a fluid in the presence of another fluid when the two
fluids are immiscible
Relative permeability : is the ratio between effective
permeability of fluid at partial saturation, and the
permeability
at
100%
saturation
(absolute
permeability).
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113
Permeability can determined from :
1. Core analysis
2. From log
3. Well test analysis ( Build up test )
4. Formation Tester (MDT , RFT )
5. NMR
Water saturation: Is the percentage
of pore volume in a rock which is
occupied by formation water.
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114
Well logging data should provide LAS
file in open hole to use it in software .
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115
1.Shale volume from GR
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116
1.1Shale volume from sp
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117
2. porosity calculation
Ø = ((ØD 2 + ØN 2)/2)1/2
ØD =(ᵨma - ᵨb)(ᵨma - ᵨf) – Vsh – (ᵨma - ᵨsh)
/ (ᵨma - ᵨf)
ØN =(CN-LCOR-0.5*Vsh*Nsh)*0.01
-Nsh = Neutron value in shale
-ᵨma =Matrix density of formation
-ᵨb = Bulk density of formation
-ᵨf = Fluid density in borehole
-ᵨsh =Shale density
-CN-LCOR= Value of matrix
-ØD = Density porosity
-ØN = Neutron porosity
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118
3. permeability calculation
Swb is set at (15 % - 25%)
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119
4. water saturation calculation
Use Archie Equation
121
120
Effective
porosity
Effective Porosity :The second step of shaly sand analysis is to determine the effective
porosity of the formation i.e. determining porosity of the formation if it
did not contain clay minerals.
Effective Porosity from Neutron-Density Combinations:
These values of neutron and density porosity corrected for the presence
of clays are then used in the equations below to determine the effective
porosity (-effective) of the formation of interest
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121
123
122
Result after interpretation
by software
Well logging data
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ormation
hrif
MA
No.
Interval
m
Thickness GR
m
API
RT
Ω.m
DT
us/ft
Neutron Density
%
g/cc
Por
%
Perm
mD
Sw
%
Vsh
%
Result
31
3735.4
3736.6
1.2
22.2
10.8
62.2
10.9
2.52
9.8
6.5
45.6
5.8
Oil
32
3744.5
3751.7
7.2
24.1
17.1
70.0
16.7
2.4
15.2
52.4
27.1
6.9
Oil
33
3771.9
3774.3
2.4
26.5
9.1
66.4
15.7
2.5
13.4
28.8
41.4
8.7
Oil
34
3809.2
3811.3
2.1
15.7
17.1
61.6
10.8
2.6
9.6
5.7
39.8
2.3
Oil
MB21 35
3811.3
3825.7
14.4
11.3
102.2
73.8
18.0
2.4
18.6
99.4
7.6
1.0
Oil
36
3825.7
3903.9
78.2
27.5
7.6
70.8
17.5
2.4
15.4
43.9
31.2
9.3
Oil
37
3930.6
3939.2
8.6
14.6
3.2
68.8
18.0
2.4
17.8
82.6
40.8
1.7
Oil
MC1 38
3939.2
3940.8
1.6
19.9
1.1
67.1
17.2
2.4
15.3
42.8
78.6
4.4
Oil & Water
39
3942.3
3946.5
4.2
18.1
1.6
64.7
16.3
2.5
13.7
27.7
75.2
3.5
Oil & Water
40
3978.7
3982.1
3.4
20.8
3.2
64.5
13.5
2.5
11.6
12.6
66.7
4.9
Oil & Water
MC2 41
3983.4
4014.5
31.1
23.2
1.7
68.4
15.7
2.4
14.4
33.1
65.8
6.3
Oil & Water
42
4022.4
4030.5
8.1
21.5
2.0
61.2
12.6
2.6
9.6
5.5
86.5
5.3
Oil-bearing water
MB11
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124
Contents
1. introduction
2. Type of well logging
3.Log interpretation
4.Some pictures for logging truck and logging tools
126
125
127
126
128
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129
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130
1
2
4
3
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