Chapter 1

Introduction

- relative permeability

- capillary pressure

Drill Cuttings- rock type

- HC indications

- porosity type

mud logs

- drilling rate

- mud properties

- gas analysis

Pressure

Transient Tests

- reservoir pressure

- permeability and skin

- fluid recovery

Cores

Special Core

Analysis

- porosity, permeability

- lithology

- residual fluid saturations

Well Logs- porosity

- lithology

- water saturation

- net pay thickness

Seismic

- structure

- gross and net thickness

- porosity

Sources of information

Mud log Schematic (Halliburton, 1991)

Mud Log Example

(Western Atlas, 1995)

Logging While Drilling

Schematic of a typical MWD

Downhole assembly (Halliburton)

Schlumberger EcoScope LWD Tool

ADR (Halliburton)

Schematic of a typical MWD

Downhole assembly (Halliburton)

Schlumberger EcoScope LWD Tool

ADR (Halliburton)

Logging While Drilling

Comparison of MWD and wireline GR logs (Halliburton)

Pressure Transient Testing

1000 10000 100000 1000000 100000003500.00

4200.00

4900.00

5600.00

6300.00

7000.00

m = -1.14e+03p* = 10397 psiap1hr = 4766 psia

Pr = 9153 psiak = 0.417 mdS = -1.98Pskin = -1965 psiaFE = 1.37rwa = 2.2 ft

Horner Time Ratio

Pw

s,

ps

ia

Semi-Log Plot - Oil Demo #2

0.1 1.0 10.0 100.0 1000.0 10000.00.1

1.0

10.0

100.0

1000.0

10000.0

CDe2S = 6.534e-01k = 0.409 mdS = -1.88C = 3.646E-04 bbl/psi

* MATCH

TD/CD and Equivalent Time, hrs

PD

/PD

' a

nd

De

lta

P;

De

riv

(+),

ps

ia

Type Curves - Oil Demo #2

Typical Core Analysis Presentation

(Helander, 1983)

Gas

Oil

Oil

Water

Computer Processed Well Log

OIL

WATER

Seismic Example

Example of Seismic data showing the correlation

between the synthetic seismogram (yellow) and the

seismic traces. Hart and Pearson (2000)

Scale

Order of magnitude

(meters)

Formation Evaluation Technique Objective

106

105

104

Satellite Imagery

Basin Geologic Studies

Seismic, Gravity, Magnetic data

Gross structure

103 Borehole Gravimeter

Ultra long spacing electic logs

Local structure

102

101

Pressure transient tests

Wireline formation tests

Productivity and recovery

100

10-1

Full diameter cores

Sidewall cores

Conventional well logs (most)

Measurement while drilling

Local values of:

Porosity

Permeability

Lithology

saturations

10-2 Micro-focused logs

Coreplug analysis

10-3

10-4

10-5

10-6

Cuttings analysis

Core analysis

x-ray mineralogy

SEM, XRD,microprobe

Local hydrocarbon content

Rock properties

Rock & clay typing

Micro-pore structure

Comparison: log – drilling time

Drilling time log (right) correlated with SP-electric log (left)

Helander (1983)

Water productive?

This Miocene sand is condensate productive from 13,060 to 13,104

feet, although the middle one-third of the sand definitely appears to be

water productive. Note the increase in SP and abrupt loss in resistivity

at 13,076 feet.

This well was conventionally cored and a 3-foot moving average

permeability curve is plotted in the SP track. The loss in permeability at

13,076 is due to change in grain size and sorting, with no significant

increase in shale content. Because of the change in deposition and

sand quality (permeability) at this depth, the formation water saturation

increases and the log resistivity decreases significantly, but the

additional water is due to increased capillarity and is not producible

water. (Corelab, 1983)

Comparison: log – core

Why Study Well Logs?

• abundant supply. Simple and

economic method of acquiring

reservoir information.

• continuous and accurate

measurements

Uses

• recognize depositional environments or

other geologic features

• correlate and map formations

• aid in interpreting seismic data

• detect overpressured zones and estimate

fracture gradients

• detection and estimation of the

potential of hydrocarbon zones.

a. oil-in-place

b. reservoir management

c. reassessment

Uses Depositional Environments

Western Atlas, 1995

Uses Geologic structures

Fundamentals of Diplog Analysis, 1987

Uses Well-to-well correlations

Schematic example of the stratigraphic slice mapping concept.

Uses detection of over-pressured zones

Overpressure detection from M’Zab Basin, Algeria

Schlumberger (1983)

Uses detection and estimation of the potential

of hydrocarbon zones

Volumetric equation for oil recovery

)()1(7758

RF

oB

wSAh

pN

How are wireline

measurements obtained?

Design questions

• Logging Speed?

• Tool length?

• Number of logging runs?

• Wellbore fluid type and level?

• Hole condition?

Example of GR-LDT-CNL logging tool

Organization

• Fundamental principles of petroleum reservoirs;

includes:

– Geology and geophysics

– Engineering concepts

Petrophysics: investigation of the physical

properties of rocks and how they relate to

measurable properties.

• Fundamental measurement theory of the various

devices

• Basic log interpretation principles

References

Corelab, Fundamentals of Core Analysis, Houston,

TX (1983)

Western Atlas, Fundamentals of Diplog Analysis,

Houston, TX (1987)

Halliburton, Openhole Log Analysis and Formation

Evaluation, Houston, TX (1991)

Helander, D.P.: Fundamentals of Formation

Evaluation, OGCI Publications,Tulsa, OK (1983)

Schlumberger, Log Interpretation Principles

/Applications, Houston, TX (1983)

Western Atlas, Introduction to Wireline Log Analysis,

Houston, TX (1995)