Tim Carr - West Virginia University

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"I am sitting inside the truck, watching a screen. The truck reels the tool back up out of the hole, slowly - more slowly than if you were reeling it in by hand - and foot by foot, the tool passes through all that dark mystery of time, emitting signals and picking up signals. I watch the tool's response to the formations it passes through on my screen, little green blips of radioactivity, and like an EKG, each blip indicates something . . .

I love to log wells. I’ve logged a thousand, and I still

find myself holding my breath when the tool first starts up out of the hole, when the electronic green lights begin to flicker and race. No one has ever before seen what I am seeing.”

OIL NOTES by Rick Bass 1989 Houghton Mifflin

Company/Seymour Lawrence. 3

Modified from SPWLA Website

PETROPHYSICS

PETROPHYSICS

GEOLOGY

DRILLING RESERVOIR

ENGINEERING

GEOPHYSICS

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In the beginning …

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Pechelbronn,

Alsace, France

September 5, 1927

SPWLA 6

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Electrical

Acoustic or Sonic

Nuclear

Geometry Hole Diameter – Rugosity

Direction – Inclination

Temperature

Pressure

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Wireline

Tubing/Pipe

MWD Measurement While Drilling

LWD Logging While Drilling

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Single Curve

A Continuous Recording of a Geophysical Parameter along a Borehole

Suite or Group of Curves

Measured or Derived Parameters

Record

Physical (Paper)

Cyber (Raster – Digital)

Logging Tool (Sonde)

Process of Logging

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Log Data to Assess Reservoir and Formations

Contracted to a Specialist Company Wireline Logs are made when drill-bit is

removed from the borehole Open-hole logs Cased-hole logs

Wireline Logging set-up Wireline Tool The Wire Winching Gear Data Analysis and Recording Equipment Data Processing and Transmission

Equipment 14

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Drilling related measurements downhole and transmitted to the surface while drilling

MWD tools are conveyed downhole as part of bottom hole assembly (BHA).

MWD systems can take several measurements (eg., gamma ray, directional survey, tool face, borehole

pressure, temperature, vibration, shock, torque etc.

Telemetry for steering well

Results transmitted digitally mud pulser telemetry

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Well logging tools conveyed into the well borehole downhole as part of the bottom hole assembly (BHA).

LWD tools work transmit measurement results to the surface via a drilling mud pulser Real Time Data Memory Data

Complete measurement results downloaded after MWD tools are pulled out of hole

LWD technology as replacement for wireline logging LWD widely used for drilling (geosteering), formation evaluation (especially for real time and high angle wells).

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Wellbore Environment Logging Speed

Borehole Diameter

Borehole Rugosity

Borehole Orientation

Mud Properties

Invaded Zone

Formation Properties

Most modern boreholes are drilled using a rotary bit in a column of circulated mud

The drilling operation creates the borehole environment in which wireline logging measurements of the rocks will be made

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Borehole size is set by the drill bit, but it is influenced by:

Changes in stress state

borehole breakout

induced fracturing

creep of salt

Chemical Reactions

swelling clays in shale

dissolution of salt

Drilling Process

spiral borehole

bit marks

What Do They Measure?

Size and shape of a recently drilled hole.

How Do They Work?

• Mechanical arms record hole size

• Hydraulic systems with calibrated

potentiometers.

How Are They Used?

• Hole size used to correct other logs

• Hole volume for cementing

• Lithologic information

•washouts indicative of formation

properties

• Stress field from hole break-out

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Deep Induction

Deep Laterlog

Short

Normal

Micospherically

Focused

Microlog

Dipmeter/FMI

Gamma ray

Neitron

Density Sonic

1000

100

10

1

0.1 0.1 1 10 100 1000

Radius of Investigation (inches)

Ver

tica

l R

eso

luti

on (

inch

es)

Seismic

NMR

Spherically

Focused

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Gamma Ray

Scintillation detector (similar to a Geiger counter) that measures the natural radiation from a formation

SP (spontaneous potential)

Measurement of the potential difference between the voltage in the wellbore and an electrode on the surface

For both logs:

Deflections to the right = Shale

Deflections to the left = Sand

Sh

ale

S

an

d

Sd

Gamma Ray

Shale Baseline

Porosity - Φ

Permeability - K, Krel

Lithology/Mineralogy

Fluid & Gas Saturations - Sw, Sg, So

Resistivity/Electrical Properties

Sonic Properties (e.g., Strength)

Bed Contacts & Thickness

Fractures (Size, Frequency, Direction)

In-situ Stress 27

The Heebner Shale

outcrop in

Lawrence:

a geiger counter

reading of “58”

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Measurement of the natural radioactivity

Principal isotopes are Potassium-40, Uranium, and Thorium (K40, U, Th)

Isotopes concentrated in clays higher radioactivity in shale

Detectors count the number of gamma rays per unit of time

Recorded in “API Units” which is 1/200th of the calibrated, standard response.

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30

6590

6610

6630

6650

6670

6690

6710

6730

6750

6770

6790

59

00

61

00

63

00

65

00

67

00

69

00

71

00

73

00

75

00

77

00

79

00

81

00

83

00

85

00

87

00

89

00

91

00

93

00

95

00

97

00

99

00

10

10

0

10

30

0

0

50

100

150

200

250

300

350

400

450

500

550

600

Wellbore Top of MarcellusTop of Target Base of TargetOnondaga Top of PurcellTop of Cherry Valley Gamma15 per. Mov. Avg. (Top of Cherry Valley)

DIP PROFILE

McCue 28-10H

NWSE

De

pth

(T

VD

)

Measured Depth

Ga

mm

a

Overall Dip = ~0.44° ; Required Inclination = 90.44°

~0.5 ~0.1

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The SP log records the electric potential between an electrode pulled up a hole and a reference electrode at the surface.

This potential exists because of the electrochemical differences between the waters within the formation and the drilling mud.

The potential is measured in millivolts on a relative scale only since the absolute value depends on the properties of the drilling mud.

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The Spontaneous Potential (SP) tool

E = -K log (aw/amf)

K is f(Temperature)

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Marine Flooding Surface

Marine Flooding Surface

Marine Flooding Surface

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Well logs give us detailed information at the location of the borehole

If there are several wells in an area, we can correlate stratigraphic units between them

The correlation is based on ‘characteristics’ of the well log responses – like a fingerprint

Often we select a datum – a correlation horizon that is registered to a common depth (flattened)

There are two main ‘philosophies’ used in well log correlation:

Correlate based on lithologic units - Lithostratigraphy

Correlate based on assume time lines – Chronostratigraphy

Which is Better? A matter of heated debate!!

AAPG©1990 reprinted with permission of the AAPG

whose permission is required for further use.

Well A Well D Well C Well B

Coastal Plain Sandstones and Mudstones

Shallow Marine Sandstones

Shelf Mudstones Van Wagoner et al., 1990

Here the correlation is based on common lithologic units

Well A Well D Well C Well B

Datum

Coastal Plain

Nearshore Sands

Shelf Mudstones

Van Wagoner et al., 1990

AAPG©1990 reprinted with permission of the AAPG

whose permission is required for further use.

Here the correlation is based on an interpretation of time-equivalent stratal packages – i.e., parasequences

Well A Well D Well C Well B

Coastal Plain

Shelf Mudstones

Van Wagoner et al., 1990

AAPG©1990 reprinted with permission of the AAPG

whose permission is required for further use.

Index

Fossil

Chronostratigraphy

Lithostratigraphy

Perhaps not for finding a field

BUT

It can impact:

- estimates of reserves

- development plans

- enhanced recovery

Based on Van Wagoner et al., 1990

Based on Van Wagoner et al., 1990

AAPG©1990 reprinted with permission of the AAPG

whose permission is required for further use.

A D

C B

A D

C B

Logs are Important for Evaluating the Subsurface History – Schlumberger Brothers (1927)

Borehole Environment - Resolution

Reservoir Evaluation

Geosteering

Correlation Lithostratigraphic

Chronostratigraphic

Geologic Interpretation Lithology

Facies

Sequence Stratigraphy

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Assignments

Reading for this week Ch. 3.2, Selley

Discuss Test on Wednesday Read Today in Energy for Tuesday (3/10) at

http://www.eia.gov/

Be Prepared to Discuss in Class - Wednesday

Discussion Leader – Andrew Hamilton