Well Logging for Earth Scientists

Transcription

1 Well Logging for Earth Scientists

2 Well Logging for Earth Scientists 2nd Edition By Darwin V. Ellis Schlumberger-Doll Research, Ridgefield, CT, USA and Julian M. Singer Richmond, UK

3 Library of Congress Control Number: ISBN (HB) ISBN (e-book) Published by Springer, P.O. Box 17, 3300 AA Dordrecht, The Netherlands. Cover illustration: F irst recorded electric log, Pechelbronn field, Sept. 5, 1927, reproduced courtesy of Schlumberger. A Manual of Solutions for the end-of-chapter problems can be found at the book s homepage at This is a second revised and enlarged edition of the first edition published by Elsevier NY, First published 2007 Reprinted with corrections 2008 Printed on acid-free paper 2007, 2008 Springer Science+Business Media B.V. No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without wri tten permission from the Publisher, with the exception of any material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work.

4 Dedication To a place where much of this was invented, elaborated, or pondered and where a friendship developed that even the writing of a book could not spoil.

5 Contents Preface Acknowledgments xvii xix 1 An Overview of Well Logging Introduction What is Logging? What is Wireline Logging? What is LWD? Properties of Reservoir Rocks Well Logging: The Narrow View Measurement Techniques How is Logging Viewed by Others? 11 References 15 2 Introduction to Well Log Interpretation: Finding the Hydrocarbon Introduction Rudimentary Interpretation Principles The Borehole Environment Reading a Log Examples of Curve Behavior and Log Display A Sample Rapid Interpretation 33 References 37 Problems 38 3 Basic Resistivity and Spontaneous Potential Introduction The Concept of Bulk Resistivity Electrical Properties of Rocks and Brines Spontaneous Potential Log Example of the SP 56 References 58 Problems 59 vii

6 viii 4 Empiricism: The Cornerstone of Interpretation Introduction Early Electric Log Interpretation Empirical Approaches to Interpretation Formation Factor Archie s Synthesis A Note of Caution The Porosity Exponent, m The Saturation Exponent, n Effect of Clay Alternative Models A Review of Electrostatics A Thought Experiment for a Logging Application Anisotropy 82 References 85 Problems 87 5 Resistivity: Electrode Devices and How They Evolved Introduction Unfocused Devices The Short Normal Estimating the Borehole Size Effect Focused Devices Laterolog Principle Spherical Focusing The Dual Laterolog Dual Laterolog Example Further Developments Reference Electrodes Thin Beds and Invasion Array Tools 118 References 121 Problems Other Electrode and Toroid Devices Introduction Microelectrode Devices Uses for R xo 129

7 ix 6.4 Azimuthal Measurements Resistivity Measurements While Drilling Resistivity at the Bit Ring and Button Measurements RAB Response Azimuthal Measurements Cased-Hole Resistivity Measurements 142 References 145 Problems Resistivity: Induction Devices Introduction Review of Magnetostatics and Induction Magnetic Field from a Current Loop Vertical Magnetic Field from a Small Current Loop Voltage Induced in a Coil by a Magnetic Field The Two-Coil Induction Device Geometric Factor for the Two-coil Sonde Focusing the Two-coil Sonde Skin Effect Two-Coil Sonde with Skin Effect Multicoil Induction Devices Induction or Electrode? Induction Log Example 174 References 176 Problems Multi-Array and Triaxial Induction Devices Introduction Phasor Induction Inverse Filtering High Resolution Induction Multi-Array Inductions Multi-Array Devices Multi-Array Processing Limitations of Resolution Enhancement Radial and 2D Inversion Dipping Beds 197

8 x 8.5 Multicomponent Induction Tools and Anisotropy Response of Coplanar Coils Multicomponent Devices 205 References 208 Problems Propagation Measurements Introduction Characterizing Dielectrics Microscopic Properties Interfacial Polarization and the Dielectric Properties of Rocks Propagation in Conductive Dielectric Materials Dielectric Mixing Laws The Measurement of Formation Dielectric Properties MHz Measurements Derivation of the Field Logs General Environmental Factors Vertical and Radial Response Dip and Anisotropy Array Propagation Measurements and their Interpretation 238 References 242 Problems Basic Nuclear Physics for Logging Applications: Gamma Rays Introduction Nuclear Radiation Radioactive Decay and Statistics Radiation Interactions Fundamentals of Gamma Ray Interactions Attenuation of Gamma Rays Gamma Ray Detectors Gas-Discharge Counters Scintillation Detectors Semiconductor Detectors 264 References 264 Problems 265

9 xi 11 Gamma Ray Devices Introduction Sources of Natural Radioactivity Gamma Ray Devices Uses of the Gamma Ray Measurement Spectral Gamma Ray Logging Spectral Stripping Developments in Spectral Gamma Ray Logging A Note on Depth of Investigation 285 References 286 Problems Gamma Ray Scattering and Absorption Measurements Introduction Density and Gamma Ray Attenuation Density Measurement Technique Density Compensation Lithology Logging Photoelectric Absorption and Lithology P e Measurement Technique Interpretation of P e Inversion of Forward Models with Multidetector Tools LWD Density Devices Environmental Effects Estimating Porosity from Density Measurements Interpretation Parameters 318 References 321 Problems Basic Neutron Physics for Logging Applications Introduction Fundamental Neutron Interactions Nuclear Reactions and Neutron Sources Useful Bulk Parameters Macroscopic Cross Sections Lethargy and Average Energy Loss Number of Collisions to Slow Down Characteristic Lengths Characteristic Times 344

10 xii 13.5 Neutron Detectors 345 References 347 Problems Neutron Porosity Devices Introduction Use of Neutron Porosity Devices Types of Neutron Tools Basis of Measurement Historical Measurement Technique A Generic Thermal Neutron Tool Typical Log Presentation Environmental Effects Introduction to Correction Charts Major Perturbations of Neutron Porosity Lithology Effect Shale Effect Gas Effect Depth of Investigation LWD Neutron Porosity Devices Summary 379 References 379 Problems Pulsed Neutron Devices and Spectroscopy Introduction Thermal Neutron Die-Away Logging Thermal Neutron Capture Measurement Technique Instrumentation Interpretation Pulsed Neutron Spectroscopy Evolution of Measurement Technique Pulsed Neutron Porosity Spectroscopy 408 References 410 Problems 413

11 xiii 16 Nuclear Magnetic Logging Introduction Nuclear Resonance Magnetometers Why Nuclear Magnetic Logging? A Look at Magnetic Gyroscopes The Precession of Atomic Magnets Paramagnetism of Bulk Materials Some Details of Nuclear Induction Longitudinal Relaxation, T Rotating Frame Pulsing Transverse Relaxation, T 2, and Spin Dephasing Spin Echoes Relaxation and Diffusion in Magnetic Gradients Measurement Sensitivity NMR Properties of Bulk Fluids Hydrogen Index Bulk Relaxation in Water and Hydrocarbons Viscosity Correlations for Crude Oils NMR Relaxation in Porous Media Surface Interactions Pore Size Distribution Diffusion Restriction Internal Magnetic Gradients Operation of a First Generation Nuclear Magnetic Logging Tool The NMR Renaissance of Inside-Out Devices A New Approach Numar/Halliburton MRIL Schlumberger CMR and Subsequent Developments LWD Devices Applications and Log Examples Tool Planners Porosity and Free-Fluid Porosity Pore Size Distribution and Permeability Estimation Fluid Typing Summary 471

12 xiv Appendix A: Diffusion 472 References 473 Problems Introduction to Acoustic Logging Introduction to Acoustic Logging Short History of Acoustic Measurements in Boreholes Applications of Borehole Acoustic Logging Review of Elastic Properties Wave Propagation Rudimentary Acoustic Logging Rudimentary Acoustic Interpretation 494 References 496 Problems Acoustic Waves in Porous Rocks and Boreholes Introduction A Review of Laboratory Measurements Porolelastic Models of Rocks The Promise of V p /V s Lithology Gas Detection and Quantification Mechanical Properties Seismic Applications (AVO) Acoustic Waves in Boreholes Borehole Flexural Waves Stoneley Waves 525 References 527 Problems Acoustic Logging Methods Introduction Transducers Transmitters and Receivers Traditional Sonic Logging Some Typical Problems Long Spacing Sonic Evolution of Acoustic Devices Arrays of Detectors 546

13 xv Dipole Tools Shear Wave Anisotropy and Crossed Dipole Tools LWD Modeling-driven Tool Design Acoustic Logging Applications Formation Fluid Pressure Mechanical Properties and Fractures Permeability Cement Bond Log Ultrasonic Devices Pulse-Echo Imaging Cement Evaluation 565 References 566 Problems High Angle and Horizontal Wells Introduction Why are HA/HZ Wells Different? Measurement Response Resistivity Density Neutron Other Measurements Geosteering Deep Reading Devices for Geosteering 589 References 593 Problems Clay Quantification Introduction What is Clay/Shale? Physical Properties of Clays Total Porosity and Effective Porosity Shale Distribution Influence on Logging Measurements Shale Determination from Single Measurements Interpretation of P e in Shaly Sands Neutron Response to Shale 613

14 xvi Response of to Clay Minerals Neutron Density Plots Elemental Analysis Clay Typing 624 References 624 Problems Lithology and Porosity Estimation Introduction Graphical Approach for Binary Mixtures Combining Three Porosity Logs Lithology Logging: Incorporating P e Other Methods Numerical Approaches to Lithology Determination Quantitative Evaluation General Evaluation Methods 648 References 650 Problems Saturation and Permeability Estimation Introduction Clean Formations Shaly Formations Early Models Double Layer Models Saturation Equations Laminated Sands Carbonates and Heterogeneous Rocks Permeability from Logs Resistivity and Porosity Petrophysical Models 676 References 681 Problems 684 Index 687

15 Preface Twenty years ago, the objectives of the first edition of this book were numerous and ambitious: to demystify the process of well log analysis; to examine the physical basis of the multitude of geophysical measurements known collectively as well logging; to clearly lay out the assumptions and approximations routinely used to extract petrophysical information from these geophysical measurements; to expose the vast range of well logging instrumentation and techniques to the larger geophysical community. Finally, there was the important goal of providing a textbook for university and graduate students in Geophysics and Petroleum Engineering, where none suitable had been available before. What s different twenty years later? First of all, Well Logging for Earth Scientists is long out of print. The petroleum industry, the major consumer of the geophysical information known as well logging, has changed enormously: technical staffs have been slashed, and hydrocarbons have become increasingly harder to locate, quantify, and produce. In addition, new techniques of drilling high deviation or horizontal wells have engendered a whole new family of measurement devices incorporated into the drilling string that may be used routinely or in situations where access by traditional wireline instruments is difficult or impossible. Petroleum deposits are becoming scarce and demand is steadily increasing. Massive corporate restructuring and the graying of the workforce have caused the technical competence involved in the search and exploitation of petroleum to become scarce. Although we are only attempting to address this latter scarcity with our textbook, the objectives are still ambitious. In this thorough updating of the text, we have attempted to include all of the new logging measurement technology developed in the last twenty years and to expand the petrophysical applications of the measurements. As in the first edition, we are primarily concerned with logging techniques that lead to formation evaluation, but mention a few other applications where appropriate. We also trace the historical development of the technology as a means of better understanding it. Throughout, large sections of the text have been set in italics, which may be skipped by the casual reader. These detailed sections may be of more interest to researchers. The goals of providing a graduate level textbook as well as a useful handbook for any practicing earth scientist (geophysicist, geologist, petroleum engineer, petrophysicist) remain. Darwin Ellis Julian Singer xvii

16 Acknowledgments The authors would like to acknowledge the special help received from a number of individuals, without which this tome could not have been achieved. Therefore we owe our thanks to: Chuck Fulton, Charlie Flaum, Richard Woodhouse, and Austin Boyd for log examples; Tom Plona, Lalitha Venkataramanan, Drew Pomerantz, Tancredi Botto, Alan Sibbit, Jacques Tabanou, Jack LaVigne, Barbara Anderson, Nikita Seleznev, and Nick Bennett for critically reviewing early versions of various chapters; John Hsu, David Johnson, Tarek Habashy, Chris Straley, and Pabitra Sen for helpful discussions; Charlie Case, Joe Chiaramonte, Laurent Mossé and especially to Mehdi Hizem for substantial contributions to the form and content of several chapters; George Stewart for the drafting of the figures; and Frank Shray, Tarek Habashy, Mark Andersen, Martin Issacs and Vicki King for help in innumerable ways with the multitude of figures. For the deficiencies, errors, and omissions, both in the text and in these acknowledgements, the blame rests with us. Darwin Ellis & Julian Singer The authors also are grateful for the use of a number of figures, in this new edition, drawn from Schlumberger s Oilfield Review. The following figures are copyright Schlumberger Ltd. Used with permission. Fig. 6.6 Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Dec xix