interpretation log

8/2/2019 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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