Logs Presentation

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Chapter 1Introduction


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- relative permeability

- capillary pressure

Drill Cuttings- rock type

- HC indications

- porosity type

mud logs

- drilling rate

- mud properties

- gas analysis

PressureTransient 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


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Mud log Schematic (Halliburton, 1991)


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Mud Log Example

(Western Atlas, 1995)


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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)


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Logging While Drilling

Comparison of MWD and wireline GR logs (Halliburton)


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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

Pws,ps

ia

Semi -Log Pl ot - 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'an

dDe

ltaP

;Der

iv(+),

ps

ia

Type Curv es - Oil Demo #2


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Typical Core Analysis Presentation

(Helander, 1983)

Gas

Oil

Oil

Water


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Computer Processed Well Log

OIL

WATER


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Seismic Example

Example of Seismic data showing the correlationbetween the synthetic seismogram (yellow) and the

seismic traces. Hart and Pearson (2000)


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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

101Pressure transient tests

Wireline formation tests

Productivity and recovery

100

10-1Full 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


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Comparison: log drilling time

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

Helander (1983)


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Waterroductive?

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 resistivityat 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 theadditional water is due to increased capillarity and is not producible

water. (Corelab, 1983)

Comparison: log core


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Why Study Well Logs?

abundant supply. Simple and

economic method of acquiring

reservoir information.

continuous and accurate

measurements


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Uses

recognize depositional environments or

other geologic features

correlate and map formations

aid in interpreting seismic data

detect overpressured zones and estimate

fracture gradients

detect ion and est imat ion o f the

po tent ial of hydro carbon zones.

a. o i l -in-p lace

b. reservo i r management

c . reassessment


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Uses Depositional Environments

Western Atlas, 1995


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Uses Geologic structures

Fundamentals of Diplog Analysis, 1987


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Uses Well-to-well correlations

Schematic example of the stratigraphic slice mapping concept.


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Usesdetection of over-pressured zones

Overpressure detection from MZab Basin, Algeria

Schlumberger (1983)


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Usesdetection and estimation of the potential

of hydrocarbon zones

Volumetric equation for oil recovery

)()1(7758RF

oB

wSAh

pN


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How are wireline

measurements obtained?

Design questions

Logging Speed?

Tool length?

Number of logging runs?

Wellbore fluid type and level?

Hole condition?


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Example of GR-LDT-CNL logging tool


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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


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Logs Presentation

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