Download - Interpretation Log
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CIT-ChE
Well Log Analysis.
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Log-Interpretation
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Basic Concepts of Log Analysis
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Contents
1. Introduction
2. Lithology
3. Porosity
4. Water Saturation
5. Permeability
6. Hydrocarbon Type and Pay Counting
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The basic log analysis:
Identification of porous and permeable reservoir rocksPorosity estimationWater saturation calculation
Differentiation between oil and gas bearing sections
Introduction
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Features of Well Logging
Formation
TO
OLs DifferentLogs
Signal Excited Signal Received
Physics Fields
Data Acquisition Logs Application
Theory,method and
experience
FormationEvaluation,et
c.
Many sorts, much data
High Vertical and bad horizontal Resolution
Badly affected by hole
Need integration with other information
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The Fundamental Questions
What kind of rock is present?
Are any hydrocarbon present? If so,should a test be run and the wellcompleted?
What kind of hydrocarbon is present: oil,gas or condensate?
How much is there (i.e., net pay,porosity, Sw, reserves)?
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Track 1: Vsh, KTrack 2: e , Vf in pore space.Track 3: Sw
Track 4: lithology, pore space.
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Lithology
The first step of log analysis is to
determine the Lithology profile (andmineral content analysis).
By Lithology identification, the loganalysts can concentrate on thesections containing potential reservoirrock.
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The Criteria to Use for Sifting
Reservoir Rocks Non-Reservoir Rocks
Low GRGood SP developmentRelative separation of resistivity curves
High GRFlat SPResistivity curves stack
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Porosity
The porosity of a formation is defined as the
volume of the pore space divided by the
volume of the rock containing the pore space.
This definition ignores the question of
whether or not the pores are interconnected.
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Porosity may be measured by a variety of methodsincluding:
Wireline logging
Core analysis;
You should not be surprised when porosityestimates from different techniques do not agree.
Measurement of Porosity
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Water Saturation-Sw
Water saturation is defined as the volumefraction of the pore space occupied by water(see following figure).
Two phases:1=So+Sw
Three phases:
1=Sg+So+Sw
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Permeability (K)
Permeability is a measure of how easilyfluids can flow through a formation.
While porosity is a static property of a rock,
permeability is a dynamic one. If flow islaminar then Darcys relation can be usedto define K in terms of flow rate (Q), area
(A), length (L), Pressure differential (P),and fluid viscosity () such that:
k=(QL)/(
PA)
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There are many ways to estimate permeability,including:
One relies upon empirical correlationsbetween porosity and irreducible water saturation
Pressure buildup from DST
Pressure draw-down and buildup from FMTLog analysis
Core analysis
Measurement of Permeability
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Hydrocarbon Type and Pay Counting
Hydrocarbon Type:
To distinguish between oil and gas, neutron-density log leave its fingerprint on theneutron/density overlay (see the plot on nextpage).
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Pay Counting:Not all of pay section willproduce hydrocarbons. Thereare low porosity shale streakswhich have no permeability, andthere are sections at the base ofthe interval that will producewater.
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Computer Center Integrated Analysis
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Reservoirproperty
information
What do our clients want to know?
We have:
Conventionallogging data
Special loggingdata
Mud logging data
Other data ...
We can offer:
Geologicalstructure
information
Other information ...
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Reservoir Property Calculation Flow Chart
Environmentalcorrection
Generate LithologyProfile
Calculate porosity, saturation andpermeability
Calculate hydrocarbon bearingzone thickness
Input logging data
Outputresults
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Lithology Profile Generated Method
t=tf* +t1*V1+t2* V2 +t3* V3b = f *+ 1 * V1 + 2 * V2+ 3 * V3
N
= f
* + 1
* V1
+ 2
* V2
+ 3
* V3
1 = + V1 + V2 +V3
V1V2V3
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Porosity Calculation
1. By sonic: S =
2. By density: D =
3. By neutron: N , use directly or need lithology correcting.
4. By 3-porosity crossplot, which can also generate Lithology
Profile. (As shown in last page)
5. By core analysis,, MRIL or other methods.
(tc tma )Cp(tf tma )
(ma
b
) Vsh
(ma
sh
)
mab
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Saturation and Permeability Calculation
Porosity()
Resistivity
Sw=( )abRw
mRt
So = 1 -- Sw
Othertransforms
Perm=0.054*4
Swi
Kint=104.4+A+3.0*lg -2.0lg(1- )
Other transforms
Saturation Permeability
n
More, click
here
m
w
n
wt
aRRF
SbRRI
0
0
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Softwares
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Logging Data Processing Results
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Logging Data Processing Results
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Basin, Tectonic belt, Reservoir, Well
Geological Problems:
- Petroleum Geology
- Petroleum Engineering
- Basic Geology
Log,Mu
dlog,Welltest,Seismic,Ge
ological
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