Fundamentals of Well-Log Interpretation1. The Acquisition of Logging Data

435 Pages·1984·11.95 MB·English

by  O. Serra (Eds.)

Developments in Petroleum Science, 15A
fundamentals of
well-log interpretation
1. the acquisition of logging data
FURTHER TITLES IN THIS SERIES
1 A.G. COLLINS
GEOCHEMISTRY OF OILFIELD WATERS
2 W.H.FERTL
ABNORMAL FORMATION PRESSURES
3 A.P. SZILAS
PRODUCTION AND TRANSPORT OF OIL AND GAS
4 C.E.B. CONYBEARE
GEOMORPHOLOGY OF OIL AND GAS FIELDS IN SANDSTONE BODIES
5 T.F. YEN and G.V. CHILINGARIAN (Editors)
OIL SHALE
6 D.W. PEACEMAN
FUNDAMENTALS OF NUMERICAL RESERVOIR SIMULATION
7 G.V. CHILINGARIAN and T.F. YEN (Editors)
BITUMENS, ASPHALTS AND TAR SANDS
8 L.P. DAKE
FUNDAMENTALS OF RESERVOIR ENGINEERING
9 K.MAGARA
COMPACTION AND FLUID MIGRATION
10 M.T. SILVIA and E.A. ROBINSON
DECONVOLUTION OF GEOPHYSICAL TIME SERIES IN THE EXPLORATION
FOR OIL AND NATURAL GAS
11 G.V. CHILINGARIAN and P. VORABUTR
DRILLING AND DRILLING FLUIDS
12 T.D. VAN GOLF-RACHT
FUNDAMENTALS OF FRACTURED RESERVOIR ENGINEERING
13 J. FAYERS (Editor)
ENHANCED OIL RECOVERY
14 G. M6ZES (Editor)
PARAFFIN PRODUCTS
Developments in Petroleum Science, 15A
well-log interpretation
1. the acquisition of logging data
0. SERRA
Former Chef du Service Dhgraphies Differkes a la Direction Exploration
de la SNEA (P), Pau, France
and
Geological Interpretation Development Manager, Schlum berger Technical
Services Inc., Singapore
(Translated from the French by Peter Westaway and Haydn Abbott)
ELSEVIER ELF AQUITAINE
Amsterdam - Oxford - New York - Tokyo 1984 Pau
ELSEVIER SCIENCE PUBLISHERS B.V.
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Distributors for the United States and Canada:
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First edition 1984
Second impression 1985
Third impression 1988
Library of Congress Cataloging in Publication Data
Serra, Oberto.
Fundamentals of well-log interpretation
(Developments in petroleum science; 15A-
Translation of: Diagraphies differees.
Bibliography: p.
Includes index.
Contents: v. 1. The aquisition of logging data.
1. Oil well logging. I. Title. II. Series.
TN87 1.35.S47 13 1984 622'. 18282 83-2057 1
ISBN 0-444-42132-7 (U.S.: V. 1)
ISBN 0-444-4213 2-7 (Vol. 15A)
ISBN 0-444-416 25-0 (Series)
@>E lsevier Science Publishers B.V., 1984
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V
PREFACE
The relentless search for elusive hydrocarbon re- training of a physicist and informatician-bringing
serves demands that geologists and reservoir en- to the field of geological analysis all the facets of
gineers bring into play more and more expertise, modern technology.
inventiveness and ingenuity. To obtain new data from Since this award, 0. Serra has, by virtue of his
the subsurface requires the continual refinement of talents as an instructor and author, acquired a very
equipment and techniques. large audience both in professional circles and in the
This book describes! the various well-logging universities studying geological sciences.
equipment at the disposal of geologists and reservoir This book is the result of a fruitful collaboration
engineers today. It follows two volumes on involving several companies. It testifies to the desire
carbonates, also published by Elf Aquitaine. of Elf Aquitaine to further an active policy of re-
One can never over-emphasize the importance to search and training, disseminating knowledge of
the geological analysis of basins, and sedimentology modern technical developments amongst its field per-
in general, of the information which drilling a bore- sonnel.
hole makes available to us. But this data would be It is hoped, that, in publishing this work, and
incomplete, even useless, if not complemented by continuing the series, we may contribute to a better
certain new techniques-well-logging in particular- understanding of geological sciences and their meth-
which represent a tremendous source of information ods, fundamental to our search for energy and mineral
both about hydrocarbons and the fundamental geol- resources.
ogy of the rocks. We also hope to strengthen the bonds between the
It required considerable enthusiasm and a de- thinkers” and the “doers”, those involved in re-
“
termination to succeed on the part of the author to search, and those on the operational side. Progress
bring the present work to its culmination, while at the depends as much on the deliberations of the one, as
same time performing the daily duties of Manager of on the techniques and skill of the other, and a close
the Log Analysis Section of the Exploration Dept. at collaboration between the two is essential. Explora-
Elf Aquitaine. tion is no longer an exclusive domain of guarded
Such qualities, indeed, earned Oberto Serra the secrets; information gathered in the course of major
first Marcel Roubault award on March 21st, 1974, in projects must, wherever feasible, be made available to
just recognition of “work concerned with methods all interested, particularly those most likely to put it
and techniques, or with ideas and concepts, which to good use.
have led to important progress in the exploration for, Finally, let us hope that, with this publication, we
and development of, natural energy resources, the might make a modest contribution to Marcel
discovery of new reservoirs, or the accomplishment of Roubault’s proud concept: “Geology at the service of
major works”. The judges recognized in particular an Man”.
invaluable liaison between the spirit of the naturalist, ALAIN PERRODON, Paris, March 1978
constantly tempered by reality, and the rigorous
This Page Intentionally Left Blank
vii
FOREWORD TO THE FRENCH EDITION
The development of hydrocarbon reservoirs fol- series on well-logging. It deals with the acquisition of
lows complex natural laws dependent on a number of log data (tool principles, logging techniques), and
factors. describes how the measurements are influenced by
The geologist’s goal is to understand the processes the many aspects of the geology of the rocks.
of hydrwarbon accumulation. For, simply, the better The second volume, currently under preparation,
these are understood, the better are the chances of will cover in detail log interpretation and applica-
discovering new hydrocarbon reserves. tions.
The fields of geological study are several: sedi-
mentology, structural geology, geochemistry, fluid
geology, geophysics. Techniques are becoming con- ACKNOWLEDGEMENTS
tinually more sophisticated to keep pace with the
demands of modern hydrocarbon exploration. I wish to express my thanks to my colleagues C.
Well-logging plays a particularly important role in Gras, L. Sulpice and C. Augier of Elf Aquitaine, for
geophysics: their continual encouragement and constructive
-well-logs provide an objective, continuous record criticism of the first volume during its initial prepara-
of a number of properties of the rocks which have tion in French for publication; to G. Herve for his
been drilled through; help in preparing the texts and figures for publica-
-they are the link between geophysical measure- tion; to P. Pain for his humorous illustrations; and to
ments on the surface, and subsurface geology; all anonymous draft-men and typists who contrib-
-they provide numerical data, introducing the uted to this book.
possibility of fairly rigorous quantification in the I also wish to express my gratitude to Schlum-
description of sedimentological processes. berger for their permission to reproduce figures and
It is no longer realistic to consider the geological texts from their various publications.
description of a reservoir without incorporating log My thanks are also extended to Dresser-Atlas,
data, Its omission would effectively exclude most of SPE of AIME, and SPWLA from whose publications
the information potentially available from drill-holes, I have borrowed numerous figures.
which itself represents a significant fraction of the Finally, I thank B. Vivet, Ph. Souhaite, J. Piger, J.
total evidence on which the description can be based. Gartner and L. Dupal of Schlumberger Technical
This book was conceived and written by a geolo- Services for their advice and criticism of the original
gist. It is hoped it will provide geologists, (and, French text; A. Perrodon for his constant support
indeed, all engineers involved in hydrocarbon ex- and encouragement; D. Bugnicourt for his advice on
ploration and reservoir development) with a good numerous points; H. Oertli for his invaluable assis-
understanding of well-logging techniques, and an ap- tance in editing and correcting the French text; and
preciation of the wealth of information available Elf Aquitaine for their permission to publish this
from log measurements, and their relevance in re- book.
servoir description.
The present work is the first of a two-volume OBERTO SERRA. Paris, March 1978
...
vlll
FOREWORD TO THE ENGLISH EDITION
Following the suggestion of several people, I de- the French text and in bringing the present volume
cided to translate my French book on Well Logging up to date.
into English. At the same time I took the opportunity 1 should also like to mention the typists responsi-
to improve and update the content by revising the ble for preparing the final draft for editing.
original texts, correcting some errors which had eluded Once again, I am indebted to H. Oertli for his help
me, and adding sections on the most recent tech- in the publication of this work, and to Elf-Aquitaine
niques. The critisms of reviewers of the original for their financial contribution without which this
French text have been taken into account. book could not have been published, and to Schlum-
It considered that this translation could best be berger for their permission to reproduce some of their
performed by my English colleagues within Schlum- material.
berger. I wish to thank Peter Westaway and Haydn
Abbott for undertaking this formidable task. Their OBERTO SERRA, Singapore, May 1982
contribution has been invaluable, both in translating
ix
CONTENTS
Preface ..................................... V 3.4.2. Environmental effects ................. 12
Foreword to the French edition .................... vii 3.4.3. Tool response ....................... 72
...
Foreword to the English edition ................... Vlll 3.5. Focused microtools ................... 12
3.5.1. The microlaterolog- MLC .............. 12
Chapter 1 . Review of basic concepts 3.5.2. The microproximity log (PL) ............. 13
1.1. The definition of a " well-log'' ............ 1 3.5.3. The micro-SFL (MSFL) ................ 73
1.2. The importance of well-logs ............. 1 3.5.4. The high-resolution dipmeter (HDT) ....... 73
1.3. The definition of rock composition ........ 2 3.6. Conclusions ........................ 14
1.3.1. Matrix ............................ 2 3.6.1. Geological factors which influence resistivity . 74
1.3.2. Shale, silt and clay .................... 2 3.6.2. Applications ........................ 15
1.3.3. Fluids ............................. 5 3.1. References ......................... 16
1.4. Rock texture and structure .............. 11
1.4.1. The relationship between porosity and resistiv- Chapter 4. The spontaneous potential -SP
ity: the formation factor ................ 12 4.1. The origin of the electrokinetic potential .... 77
1.4.2. The relationship between saturation and resis- 4.2. The origin of the electrochemical potential ... 19
tivity: Archie's formula ................. 14 4.2.1. Membrane potential ................... 19
1.4.3. The effect of shaliness on the resistivity ..... 15 4.2.2. Liquid junction or diffusion potential ....... 80
1.4.4. The effect of shale distribution ... 15 4.2.3. The electrochemical potential. E, .......... 80
1.4.5. Permeability ........................ 18 4.3. Ionic activity. concentration and resistivity ... 80
1.4.6. Thickness and internal structure of strata .... 23 4.4. The static SP ........................ 81
1.5. Conclusions ........................ 24 4.5. Amplitude and shape of SP peaks ......... 82
1.6. ...................... 24 4.5.1. Hole diameter .......... 82
4.5.2. Depth of invasion ....... 82
Chapter 2 . Logging techniques and measurements 4.5.3. ................. 82
2.1. Classification of log measurements 29 4.5.4. ................. 83
2.1.1. Natural phenomena ................... 29 4.5.5. Tight formations ..................... 84
2.1.2. Physical properties measured by inducing re- 4.5.6. Shale base-line shifts, and drift ........... 84
sponses from the formation ...... 29 4.5.7. Irregular invasion profile ............... 85
2.2. Problems specific to well-log measurements . . 30 4.5.8. SP anomalies ........................ 85
2.2.1. Borehole effects. invasion ............... 31 4.6. Geology and the SP ................... 86
2.2.2. The effect of tool geometry .............. 33 4.6.1. Composition of the rock ................ 86
2.2.3. Logging speed ............... 36 4.6.2. Rock texture ........................ 88
2.2.4. Hostile environments .................. 38 4.6.3. Temperature .............. ... 88
2.3. Loggng equipment-surface and downhole . . 38 4.6.4. Pressure ........................... 88
2.3.1. Logging truck and off 39 4.6.5. Depositional environment, sequential evolu-
2.3.2. Cable ............................. 39 tion 88
2.3.3. The logging tool .............. 43 4.1. .................. 88
2.3.4. Recording equipment .................. 44 4.8. References ......................... 88
2.3.5. Tool combinations . . 45
2.3.6. Memorization ..... 45 Chapter 5. An introduction to nuclear logs
2.4. Log presentation ..................... 46 5.1. Definition .......................... 89
2.5. Repeatability and calibrations ............ 48 5.2. Recording capability .................. 89
2.6. Data transmission .............. 48 5.3. Statistical variations ................... 89
2.7. References ......................... 50 5.4. Dead-time .......................... 90
5.5. Logging speed ....................... 91
Chapter 3. The measurement of resistivity 5.6. Bed thickness ....................... 91
3.1. Introduction ........................ 51 5.1. Measuring point ..................... 93
3.2. Non-focused long-spacing tools ........... 51 5.8. References ......................... 93
3.2.1. Measuring principle ................... 51
3.2.2. The current path ..................... 53 Chapter 6. Measurement of the nature1 gamma radioactiv-
3.2.3. Measuring point ..................... 53 itr
3.2.4. Radius of investigation ................. 54 6.1. Definition natural radioactivity ........... 95
3.2.5. Environmental corrections .............. 54 6.2. Basic concepts ....................... 95
3.2.6. The shape of the apparent resistivity curve ... 55 6.2.1. a-radiation ......................... 95
3.3. Focused long-spacing tools .............. 57 6.2.2. ,&radiation. /3+ or fi- .................. 96
3.3.1. Induction-IL ...................... 51 6.2.3. y-radiation ......................... 96
3.3.2. The laterologs-LL ................... 64 6.2.4. Radioactive decay .................... 96
3.3.3. The spherically focused log-SFL ......... 61 6.2.5. Radioactive equilibrium ................ 97
3.4. Non-focused microtools: the microlog (ML) . . 71 6.2.6. The units of radioactivity ............... 98
3.4.1. Principle ........................... 11 6.3. The origin of natural radioactivity in rocks ... 99