Principles of Mathematical Petrophysics International Association for Mathematical Geosciences STUDIES IN MATHEMATICAL GEOSCIENCES 1. William B. Size, Editor Use and Abuse of Statistical Methods in the Earth Sciences 2. Lawrence J. Drew Oil and Gas Forecasting: Relections of a Petroleum Geologist 3. Ricardo A. Olea, Editor Geostatistical Glossary and Multilingual Dictionary 4. Regina L. Hunter and C. John Mann, Editors Techniques for Determining Probabilities of Geologic Events and Processes 5. John C. Davis and Ute Christina Herzfeld, Editors Computers in Geology—25 Years of Progress 6. George Christakos Modern Spatiotemporal Geostatistics 7. Vera Pawlowsky-Glahn and Ricardo Olea Geostatistical Analysis of Compositional Data 8. P.J. Lee Statistical Methods for Estimating Petroleum Resources 9. John H. Doveton Principles of Mathematical Petrophysics Principles of Mathematical Petrophysics John H. Doveton Kansas Geological Survey 3 3 Oxford University Press is a department of the University of Oxford. It furthers the University’s objective of excellence in research, scholarship, and education by publishing worldwide. Oxford New York Auckland Cape Town Dar es Salaam Hong Kong Karachi Kuala Lumpur Madrid Melbourne Mexico City Nairobi New Delhi Shanghai Taipei Toronto With oices in Argentina Austria Brazil Chile Czech Republic France Greece Guatemala Hungary Italy Japan Poland Portugal Singapore South Korea Switzerland hailand Turkey Ukraine Vietnam Oxford is a registered trademark of Oxford University Press in the UK and certain other countries. Published in the United States of America by Oxford University Press 198 Madison Avenue, New York, NY 10016 © Oxford University Press 2014 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, by license, or under terms agreed with the appropriate reproduction rights organization. Inquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, at the address above. You must not circulate this work in any other form and you must impose this same condition on any acquirer. Library of Congress Cataloging-in-Publication Data Doveton, John H., 1944– Principles of mathematical petrophysics / John H. Doveton. pages cm Includes bibliographical references and index. ISBN 978–0–19–997804–5 (alk. paper) 1. Petrology—Mathematical models. 2. Mineralogy—Mathematical models. 3. Rocks. I. Title. QE431.6.P5D68 2014 552.00151—dc23 2014001402 9 8 7 6 5 4 3 2 1 Printed in the United States of America on acid-free paper Dedicated with thanks and remembrance of good times to the Mathematical Geology Section and the Energy Research Section of the Kansas Geological Survey, without whose work and inspiration, this book would not have been possible. CONTENTS Foreword to the Series xi Preface xiii Acknowlegements xv 1. Fluid Saturation Evaluation 1 he Archie equations 1 he Humble equation and its variants 4 Sensitivity analysis of Archie equation parameters 8 Non-Archie sandstones 10 Shaly sandstone analysis 13 Double-layer shaly sandstone models 15 Dual-water shaly sandstone models 20 he Archie equation in carbonate rocks 23 Porosity partitioning in dual-porosity systems 26 he porosity exponent in a triple-porosity system 31 Dielectric logging measurement of the porosity exponent 31 Petrographic evaluations of the porosity exponent in carbonates 32 he saturation exponent, n 33 Wettability efects on the saturation exponent 36 Archie redux 38 2. Porosity Volumetrics and Pore Typing 44 Porosity of spherical packs 44 Clastic “efective” porosity 44 Neutron-density shale volumetrics 45 Gamma-ray estimations of shale volume 47 Correction of total porosity for shale contents 50 Allocation between shale morphology types 51 Carbonate porosity 55 Vug porosity evaluation from acoustic and resistivity logs 56 NMR logging of vuggy porosity 62 3. Permeability Estimation 67 Permeability is a vector 67 Prediction of permeability from porosity 67 Flow-zone indicator (FZI) discrimination of hydraulic units 69 Application of FZI to permeability prediction 73 Permeability predictions from porosity and “irreducible” water saturation 77 NMR estimation of permeability in clastic pore systems 79 Permeability estimation in carbonates dominated by interparticle porosity 81 Evaluation of permeability in dual- and triple-porosity systems 82 A Wilderness of mirrors 88 4. Compositional Analysis of Mineralogy 94 Some matrix algebra 94 Compositional-solution evaluation 97 Underdetermined systems 99 Overdetermined systems 102 Optimization models for compositional solutions 103 Multiple-model solutions of rock composition 105 Elucidation of clay minerals 106 Compositional analysis from geochemical logs 113 Inversion mapping of compositions 117 5. Petrophysical Rocks: Electrofacies and Lithofacies 122 Facies and electrofacies 122 Dunham textures and electrofacies 123 Petrophysical recognition of lithofacies 124 Zonation by cluster analysis 128 heoretical, empirical, and interpretive electrofacies methods 131 Principal component analysis (PCA) of electrofacies 134 Classiication by a parametric electrofacies database 146 Supervised electrofacies analysis methods 147 Electrofacies classiication by discriminant function analysis (DFA) 148 Nonparametric discriminant analysis 152 Neural-network prediction of lithofacies from logs 157 Beyond product facies to the petrophysical prediction of process facies 162 6. Pore-System Facies: Pore hroats and Pore Bodies 171 he petrofacies concept 171 Equivalent hydraulic radius of tubes 172 Capillary pressure evaluation of pore-throat sizes 172 he Winland equation 176 he low-unit concept 178 Petrofacies case-study applications of the Winland equation 179 Carbonate petrofacies pore-throat size distributions 185 Pore-body size distributions from NMR measurements 198 NMR facies in sandstones 200 NMR pore-size interpretation in carbonates 204 NMR-partitioned porosity and Dunham textural classes 205 NMR facies in carbonates 209 [viii] Contents 7. Saturation-Height Functions 217 Integration: the saturation-height model 217 he basics of reservoir saturation proiles 218 Saturation-height modeling in sandstones from capillary pressure measurements 221 Height functions for bulk-volume water 225 Permeability-height functions 230 Saturation-height modeling in carbonates 233 Saturation-height modeling based on magnetic resonance logs 238 Putting it all together: the static reservoir model 241 Index 245 Contents [ix]
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