Openhole Log Analysis and Formation Evaluation

667 Pages·2012·63.14 MB·English

by  Richard M. Bateman

Openhole
Log Analysis and
Formation Evaluation
SECOND EDITION
Richard M. Bateman
Openhole Log Analysis
and Formation Evaluation
SPE-OLA-12-0101-Book.indb 1 28/07/12 3:57 AM
Openhole Log Analysis
and Formation Evaluation
Richard M. Bateman
Faculty Member, Texas Tech University
Second Edition
Society of Petroleum Engineers
SPE-OLA-12-0101-Book.indb 3 28/07/12 3:57 AM
© Copyright 2012 Society of Petroleum Engineers
All rights reserved. No portion of this book may be reproduced in any form or by any means,
including electronic storage and retrieval systems, except by explicit, prior written permission of
the publisher except for brief passages excerpted for review and critical purposes.
Printed in the United States of America.
Disclaimer
This book was prepared by members of the Society of Petroleum Engineers and their well-
qualified colleagues from material published in the recognized technical literature and from their
own individual experience and expertise. While the material presented is believed to be based on
sound technical knowledge, neither the Society of Petroleum Engineers nor any of the authors or
editors herein provide a warranty either expressed or implied in its application. Correspondingly,
the discussion of materials, methods, or techniques that may be covered by letters patents implies
no freedom to use such materials, methods, or techniques without permission through appropriate
licensing. Nothing described within this book should be construed to lessen the need to apply
sound engineering judgment nor to carefully apply accepted engineering practices in the design,
implementation, or application of the techniques described herein.
ISBN 978-1-61399-156-5
ISBN 978-1-61399-269-2 (Digital)
Society of Petroleum Engineers
222 Palisades Creek Drive
Richardson, TX 75080-2040 USA
http://www.spe.org/store
[email protected]
1.972.952.9393
SPE-OLA-12-0101-Book.indb 4 28/07/12 3:57 AM
Preface
Formation evaluation is an extremely broad term and can encompass many different disciplines.
Thus, any work that includes the phrase in its title runs a double risk. An attempt to cover all
possible methods of data gathering and analysis would appear presumptuous and overly ambi-
tious, and yet the omission of any of the methods would rightly leave the work incomplete. In its
broadest sense, formation evaluation can include everything from macroscopic studies of an entire
geologic basin down to microscopic studies of individual mineral grains. Central to both extremes
are borehole geophysical well logs. In the practical sense, each formation evaluation method leans
on its neighbor for support. Seismic interpretation can be refined in the light of logging data, log
response can be calibrated by reference to core analysis, flow testing can refine log-based produc-
tivity estimates, etc.
It is this interaction between a spectrum of different formation evaluation methods that makes
the whole process of evaluating subsurface formations a dynamic and viable science. Thus,
although logs and log analysis are central to this work, it should never be thought that logs alone
are sufficient to define entirely the properties of a formation.
The student of formation evaluation should therefore be familiar with geology, geophysics, geo-
chemistry, petrophysics, reservoir engineering, drilling technology, computer science, economics,
mathematics, and probability theory. Few occupations require such a wide overall familiarity with
so many disciplines. Unfortunately, this has led the formation evaluator to be labeled as the jack
of all trades and master of none. However, because of an awareness of the interaction between
so many disciplines, he or she is in fact a better master of many trades than many of the jacks of
individual ones. It is hoped that this work reflects these sentiments by stressing the fruitfulness
of combining neighboring sciences to produce a whole that is greater than the sum of its parts.
This book is divided into sections that address a number of formation evaluation themes. Part I,
Methods of Gathering Formation Evaluation Data, includes Chapters 1 through 5. These chapters
address methods of gathering data needed to evaluate a formation. Chapters 6 through 8 comprise
Part II, Methods of Analysis and Application of Results, and discuss analysis methods in general
and the end use of the results of analysis. Part III, Openhole Logging Measurements (Chapters
9 through 20), addresses openhole logging measurements; each tool’s principle of operation and
contribution to the overall evaluation problem is covered. Part IV, Analysis of Logs and Cores,
includes Chapters 21 through 30. These chapters address more subtle details of log analysis and
its integration with core analysis. In Part V, Formation Testing, Chapters 31 and 32 cover forma-
tion testing. Part VI, Integrated Formation-Evaluation Plan, consists of Chapter 33. This final
chapter gives an overall “game plan” for the formation evaluator. An appendix to the volume sum-
marizes important log analysis equations.
Since the first publication of this book in 1985, the science and art of formation evaluation has
seen many innovations. In particular, measurements of formation resistivity have advanced with
the introduction of array tools that allow improved measurement of formation resistivity at a range
of distances from the borehole itself. Likewise, advances in the design of sonic tools and in the
processing of their recorded signals afford the analyst a better insight into the nature of the rocks
surrounding the borehole. Also, new methods of looking at the distribution of pore sizes, their
fluid content, and formation flow potential have come into wide use with advances in microcore
scanning, nuclear magnetic resonance technology, and wireline formation testing improvements.
SPE-OLA-12-0101-Book.indb 5 28/07/12 3:57 AM
Finally, what was previously considered unworthy of consideration is now the item on which
many analysts spend the majority of their time, namely shales!
Apart from the tools themselves, and their additions to the petrophysicists arsenal, the mode of
data capture, too, has changed. Whereas previously all data was recorded from a wireline logging
tool suspended on a cable, today many, if not all, of the conventional wireline measurements can
be made from logging while drilling tools run on the end of the drillpipe itself. Thus, this revised
and updated edition will prepare the reader for a fuller understanding of modern formation evalu-
ation data gathering methods as well as illuminate advanced analysis techniques afforded by these
new and improved sensors.
SPE-OLA-12-0101-Book.indb 6 28/07/12 3:57 AM
Acknowledgments
This work is based on many years of practical experience with the vicissitudes of evaluating
subsurface formation properties. In the course of compiling materials, I have leaned heavily on
friends, coworkers, other authors, oil companies, service companies, and professional societies.
Where humanly possible, I have given credit where credit is due. In some cases, it has proved dif-
ficult to trace the origin of some figures, and I must thank those who have unknowingly assisted
me with such material. I also owe a debt of gratitude to the many students who have attended my
courses and provided me with valuable feedback on both the style and content of this work.
I also owe a debt of gratitude to Tarek Ghazi, who volunteered his time for the thankless task of
being my go-between with the SPE Books Development Committee. Lastly, this revised edition
would have been much the poorer if it had not been for the dedicated industry professionals who
reviewed the manuscript and provided invaluable suggestions for its improvement. They included
Matt Bratovich, Quinn Passey, Dare Keelan, Jeff Williams, Professor Richard Dawe, and Profes-
sor Donald Hill.
My thanks to Jennifer Wegman of the SPE, without whose tireless efforts the publication of this
work would have been impossible.
Richard M. Bateman
Canton, North Carolina
April 2012
SPE would like to thank Tarek Ghazi for his generous contributions to the oversight of this book
project on behalf of the Books Development Committee. We appreciate his contributions in work-
ing with the author and ensuring that timelines and quality standards were upheld throughout the
process.
SPE-OLA-12-0101-Book.indb 7 28/07/12 3:57 AM
Contents
Preface ............................................................................................................................v
Acknowledgments .......................................................................................................vii
Part I—Methods of Gathering Formation Evaluation Data ........................................1
1. Formation Evaluation Overview ..............................................................................3
1.1 The Scope of Formation Evaluation....................................................................3
1.2 Formation Evaluation ..........................................................................................3
1.3 Formation-Evaluation Methods ...........................................................................5
1.4 Mud Logging ......................................................................................................6
1.5 Coring ................................................................................................................6
1.6 Measurements While Drilling (MWD) ..................................................................7
1.7 Logging While Drilling (LWD) ..............................................................................7
1.8 Testing ...............................................................................................................7
1.9 Openhole Logging .............................................................................................7
1.10 Modern Logging Tools ........................................................................................8
1.11 Evolution of Logging Devices .............................................................................9
1.12 Categorization of Logging Devices ...................................................................11
1.13 Summary ..........................................................................................................15
2. Mud Logging ...........................................................................................................39
2.1 Measurements Related to the Drilling Process ................................................39
2.2 Measurements Relevant to Formation Evaluation ............................................40
2.3 Measurement Techniques .................................................................................41
2.4 Summary ...........................................................................................................45
3. Measurements on Drillpipe ....................................................................................59
3.1 Terminology: MOD, MWD, and LWD .................................................................59
3.2 MOD Telemetry .................................................................................................60
3.3 Morphing From Wireline to MOD ......................................................................62
3.4 Petrophysical Considerations for MOD Measurements ....................................63
3.5 Logs Provided by MOD .....................................................................................64
3.6 Other MOD Sensors .........................................................................................66
3.7 MOD Quality Control and Sensor Calibration ...................................................66
3.8 The Future of MOD ...........................................................................................68
4. Wireline Logging Operations .................................................................................71
4.2 Logging Trucks ..................................................................................................71
4.3 Logging Cables .................................................................................................73
4.4 Logging Tools ....................................................................................................77
4.5 The Borehole Environment ...............................................................................79
4.6 Choosing a Logging Suite ................................................................................81
4.7 Computerized Logging Units ............................................................................84
4.8 Log-Quality Control ...........................................................................................87
5. Coring ......................................................................................................................93
5.1 Objectives .........................................................................................................93
5.2 Wireline Coring .................................................................................................93
SPE-OLA-12-0101-Book.indb 9 28/07/12 3:57 AM
5.3 Conventional Coring .........................................................................................96
5.4 Coring Fluids ....................................................................................................97
5.5 Special Core Handling ......................................................................................99
5.6 Summary ........................................................................................................100
Part II—Methods of Analysis and Application of Results ......................................101
6. The Physics of Rock/Fluid Systems ....................................................................103
6.1 The Genesis of Reservoir Rocks ....................................................................103
6.2 Fluid Distribution in the Reservoir ...................................................................106
6.3 Relative Permeability ......................................................................................109
6.4 Measurement of Porosity ................................................................................113
6.5 Measurements of Permeability .......................................................................113
6.6 Measurements of Saturation ..........................................................................116
6.7 Practical Petrophysics .....................................................................................120
6.8 Averaging ........................................................................................................120
6.9 Summary ........................................................................................................123
7. Basic Concepts of Log Analysis .........................................................................125
7.1 Log Analysis Overview ...................................................................................125
7.2 Lithology .........................................................................................................126
7.3 Porosity ...........................................................................................................127
7.4 Water Saturation: S .......................................................................................131
w
7.5 Hydrocarbon Type ...........................................................................................132
7.6 Pay Counting ..................................................................................................133
7.7 Permeability ....................................................................................................134
7.8 Generalized Log Analysis ...............................................................................134
7.9 Summary ........................................................................................................136
8. Volumetrics and Reserve Estimation ..................................................................139
8.1 Oil and Gas in Place Estimates ......................................................................139
8.2 Reserve Estimates .........................................................................................141
8.3 Recovery Factors ............................................................................................141
8.4 Formation Volume Factors ..............................................................................142
8.5 Depth and Net Pay Measurements .................................................................142
8.6 Special Cases of Deviated Wells and Dipping Beds .......................................143
8.7 Reservoir Volumes ..........................................................................................147
8.8 Reserves ........................................................................................................148
8.9 Uncertainty .....................................................................................................149
Part III—Openhole Logging Measurements ............................................................153
9. The Spontaneous Potential Log ..........................................................................155
9.1 History of the Spontaneous Potential (SP) .....................................................155
9.2 Recording the SP ...........................................................................................155
9.3 Source of the SP ............................................................................................156
9.4 R From the SP ..............................................................................................159
w
9.5 Alternative One-Step Method for Obtaining R From the SP .........................166
w
9.6 Factors Affecting the SP .................................................................................168
9.7 The SP as a Shale Indicator ...........................................................................172
9.8 SP Depositional Patterns ................................................................................173
9.9 SP Quality Control ..........................................................................................173
10. The Gamma Ray Log...........................................................................................179
10.1 Origin of Natural Gamma Rays .....................................................................179
10.2 Abundance of Naturally Occurring Radioactive Minerals .............................180
10.3 Operating Principle of Gamma Ray Tools .....................................................180
10.4 Calibration of Gamma Ray Detectors and Logs ...........................................180
SPE-OLA-12-0101-Book.indb 10 28/07/12 3:57 AM
10.5 Time Constants .............................................................................................182
10.6 Perturbing Effects on Gamma Ray Logs ......................................................185
10.7 Estimating Clay Content From Gamma Ray Logs ........................................186
10.8 Gamma Ray Spectroscopy ...........................................................................189
10.9 Interpretation of Gamma Ray Spectral Logs ................................................191
10.10 Summary ......................................................................................................194
11. Resistivity Measurements ..................................................................................203
11.1 Definitions .....................................................................................................203
11.2 Typical Resistivities .......................................................................................204
11.3 Ideal Resistivity Measurements ....................................................................204
11.4 Evolution of Modern Resistivity Devices .......................................................208
11.5 Philosophy of Measuring Formation Resistivity ............................................209
11.6 Summary ......................................................................................................209
12. Induction Logging ...............................................................................................213
12.1 Induction Basics ...........................................................................................213
12.2 When To Use an Induction Logging Device ..................................................214
12.3 Induction-Tool Development History .............................................................214
12.4 Theory of Induction Devices .........................................................................215
12.5 Practice of Induction Logging .......................................................................216
12.6 Phasor Induction ...........................................................................................223
12.7 High-Resolution Induction ............................................................................223
12.8 Array Induction Tool (AIT) .............................................................................225
12.9 3D Induction ................................................................................................226
12.10 Calibration ....................................................................................................226
12.11 Summary ......................................................................................................228
13. The Laterolog.......................................................................................................231
13.1 Early Laterolog Devices ................................................................................231
13.2 When To Use a Laterolog .............................................................................231
13.3 The DLL Tool .................................................................................................232
13.4 Borehole and Invasion Corrections ...............................................................237
13.5 The Butterfly Chart .......................................................................................239
13.6 DLL Fingerprints ...........................................................................................240
13.7 Anomalous Behavior.....................................................................................241
13.8 Summary ......................................................................................................245
14. Microresistivity Measurements .........................................................................249
14.1 Microresistivity Tools .....................................................................................249
14.2 Depth of Investigation ...................................................................................253
14.3 Bed Resolution .............................................................................................254
14.4 Environmental Corrections ...........................................................................254
14.5 S and Hydrocarbon Movability ....................................................................256
xo
14.6 Hydrocarbon Density ....................................................................................257
14.7 Calibration and Quality Control .....................................................................258
15. Dielectric Measurements ...................................................................................259
15.1 Electromagnetic Propagation Tools (EPT) ....................................................259
15.2 Physical Principle .........................................................................................259
15.3 Measurement Principles for Dielectric Logging Tools ...................................261
15.4 Summary ......................................................................................................270
16. Sonic (Acoustic) Logging and Elastic Formation Properties .........................273
16.1 Propagation of Elastic Waves .......................................................................273
16.2 Elastic Constants ..........................................................................................274
16.3 Sonic Logging Tools ......................................................................................275
SPE-OLA-12-0101-Book.indb 11 28/07/12 3:57 AM