FOR PETROLEUM GEOLOGISTS AND ENGINEERS

. 4

SEPM SHORT COURSE NO. 22

SEAS;

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byEric Eslinger and David Pevear

SUM SHORT COURSE NOTES NO. 22

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Additional copies of this publicationmay be ordered from SEPM. Send your order to:

SEPM Post Office Box 4756 Tulsa, OK 74159-0756 U.S.A. C Copyright 1988 by Society of Economic Paleontologists and Mineralogists Printed in the of America

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Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3801090/9781565762497_frontmatter.pdf by guest on 27 September 2021 PREFACE

These notes provide a general introduction of clays for the uninitiated, plus a review of traditional and more recent concepts for those who already know something about clays. Some topics were reviewed more intensively than others, either because a recent review had not been made, a concept was relatively new or thought particularly important, orthere was perceived to be

some misunderstanding about a concept. The concept of fundamental

particles and the phenomenon ofinterparticle diffraction, relatively new concepts that arereshaping the manner of visualizing mixed-layer clays, are discussed in somedetail. A discussion of shaly-sandlog analysis, from a claymineralogy perspective, is included. Isotope geology is discussed because of its potential for permitting a better understanding of temperatures and timing of . The role of clay minerals in diagenesis, per se,is only cursorily reviewed; references are given to reviews and compendiums on sandstone diagenesis, of which the role of clays is but a part.

We have not attempted to make a complete literature search on any of the chapter topics, so unintentional omissions of some concepts or individual "good" published papers can be

expected. We have collaborated to some extent on some of the

chapters, but primary responsibility for chapters 1,2,4,5, and

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Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3801090/9781565762497_frontmatter.pdf by guest on 27 September 2021 the appendix was that of Pevear, and primary responsibility for chapters 3,6, 7, 8, and 9 was that of Eslinger.

We would like to thank the many people with whom we have had discussions concerning clays during the writing of this text. These include Craig Calvert, Jenny Colten-Bradley, Denny Eberl, Reed Glassman, Wuu-Liang Huang, Jim Hoffman, Bob

Klimentidis, Leo Lynch, Elizabeth Nicot, Rich Pollastro,Gray Thompson, Bruce Velde, and Gene Whitney. In particular, we thank Jim Howard and Robert Elphick for reviewing thechapter on logs; their suggestions were very helpful. Also, Craig Calvert contributed to an earlier version ofsome of the material in this

volume. We thank him for allowing us to edit anduse his material.

In addition, we thank Sharon Blassingame forlogistical support. Finally, we thank Cities Service Oil andGas Corporation (EE) and Exxon Production Research Company (DP)for permitting us to participate in this exercise.

Eric Eslinger, Tulsa David Pevear, Houston

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Chapter 1. INTRODUCTION

Definitions . . 1-1 Clay ... . 1-1 Clay 1-1 Who Studies Clays 1-3 Distribution and Origin of Clay Minerals . 1-5

Chapter 2. STRUCTURE OF BASIC GROUPS, AND INTERPRETATION OF CLAY MINERAL DATA Basic Structural Elements 2-1

The Silica . .. . 2-1

The Tetrahedral Sheet . 2-3 The Octahedral Sheet 2-3 Basic Layer Types 2-5 The 1:1 Layer . 2-5

The 2:1 Layer . . 2-6 Classification and

Nomenclature of Phyllosilicate Clays . . 2-10 Criteria for Classification 2-10 Interpretation of Clay Mineral Data 2-11

General . . 2-11 Classification of the Serpentine-Kaolin Group,

and Interpretation of XRD Data . . .. . 2-13

Serpentine Subgroup , 2-17

Kaolin Subgroup . . 2-18 Interpretation of XRD Data 2-21 Classification of the - Group,

and Interpretation of XRD Data . . . 2-23 Classification of the Group, and Interpretation of XRD Data 2-28

Trioctahedral . 2-29 Dioctahedral Micas . 2-31 Interpretation of XRD Data 2-35 Classification of the -Smectite Group, and Interpretation of XRD Data 2-36 Vermiculite Group . 2-36 Smectite Group 2-40

Saponite Group . 2-41 Subgroup . 2-44 Interpretation of XRD Data 2-47 Air-dried Analysis 2-47 Solvation with Ethylene Glycol or Glycerol 2-49

Heat Treatments . . 2-51

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TABLE OF CONTENTS (Continued)

Page Chapter 2 (Continued) Classification of the ,

and Interpretation of XRD Data . , -. 2-52 Interpretation of XRD Data ...... 2-61 Classification of the -

Group, and Interpretation of XRD Data . 2-62 Interpretation of XRD Data . .. . I. 2-64 Classification of Associated Minerals,

and Interpretation of XRD Data ...... 2-64 I XRD Data from Randomly and Preferentially

I Oriented Samples .. . . il Preferred Orientation . 2-71 Random Orientation . . 2-79 Kaolin Polytypes . 2-82 Disordered . . 2-84 . . . . . 2-85

Hi Smectite 2-85

Dioctahedral Mica Polytypes . . . . 2-86 Chlorite Polytypes ...... 2-87

Mixed-layer Clay Minerals . . . .. J. 2-88 Classification and Nomenclature . 2-88 Layer Types 2-89

1 II Stacking Arrangement ...... 0 2-91

1 Regular Interstratification . . . . 2-91

: Segregation into Crystallites . 1 2-97 Random Mixed-Layering . . . 2-97 Regular Mixed-Layering 2-98 ! Interpretation of XRD Patterns of Mixed- Layer Clays 2-100 Recognition of Mixed Layering. . . . 2-101 . Determination of Types of Layers . . 2-108 Determination of Proportion and Ordering . I...... 2-111 Qualitative Method . 2-111 Quantitative Method . 2-117 Fundamental Particle Concept . . 2-129 Chapter 3. PROPERTIES Introduction ...... 3-1 Charge ...... 3-1 Structural versus Surface Charge o . .. . . 3-1 Zero Point of Charge . 3-4 Diffuse Double Layer Theory . .. . 3-8

Gouy-Chapman Model . . 3-8 Stern Model . . . . . 3-10 Water of Hydration 3-12 vi

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Chapter 3 (Continued) 3-13 Fixing of Cations . . 3-13 Swelling . . Deflocculation versus Dispersion . . 3-17 3-17 Cation Exchange Capacity . . . . 3-20 Surface Area . .

Chapter 4. CLAY MINERALS IN MODERN 4-1 Introduction . . . . . 4-2 Clays as Environmental Indicators . 4-3 Clay Origins . Modern Detrital Sediments 4-3 . 4-4 Bedrock Sources . . . Sources . . . 4-5 Transport of Clays 4-6

. 4-9 Clays in Modern Oceanic Sediments . 4-16 Modern Authigenic Clay .. . 4-19 Extension to Ancient Rocks . . . . .

Chapter 5. DIAGENESIS Introduction 5-1 5-4 The Evidence: /Depth Relationships . .. Nature of the Reaction . . 5-11 5-16 Controls on the Reaction . .. . Relation to Petroleum Geology . . . . 5-24 Clay-Organic Relations . 5-25 Temperature and Maturation . 5-26

. . 5-33 Migration .

. . . 5-36 Overpressuring . . . 5-42 Sandstone Cementation . . .

Chapter 6. CLAY MINERALS AND SANDSTONE DIAGENESIS 6-1 Introduction . Effect of Clay Minerals on Porosity 6-2 6-2 Compaction . 6-4 Clay Infiltration . . 6-6 Neoformed Clays . . 6-7 Transformed Clays ...... 6-8 Effect of Clays on Cementation . . Differential Cementation in 6-10 Secondary Porosity and Clay Minerals 6-16 Clay Mineral Trends During SandstoneDiagenesis . . 6-18 Gulf Coast-Style Sandstone Diagenesis 6-21 6-22 Clay Minerals in Volcanic Sandstones . . 6-23 Porosity Prediction in Sandstones . . .

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Page Chapter 7. ISOTOPE OF CLAY MINERALS Isotope Geothermometry 7-1

Hydrogen and Oxygen Isotopes in Formation Waters . . . 7-9 K-Ar Dating of Sedimentary Clay Minerals .. 7-16 Background 7-16

K-Ar Dating of Illite and Illite/Smectite . . 7-17 Gulf Coast . 7-17

North Sea . 7-20 Rb-Sr Systematics in Sediments, Clays, andWaters . 7-20 Background ...... 7-20

87Sr/86Sr Ratios inCrustal Materials . 7-22 Rb-Sr Dating of Rocks . . 7-24

Evolution of 87Sr/86Sr in the Ocean . . . 7-24 Rb-Sr Dating of ...... 7-26 Rb-Sr Dating of Clay Minerals 7-27 ...... 7-27

Illites . . . . 7-27

Illite/Smectite . . . . 7-28 Chapter 8. CLAYS AND PRODUCTION PROBLEMS Introduction 8-1 Effect of Clays on Porosity-Permeability Trends . . 8-1 Clays and Rock "Sensitivity" to Water . . . . 8-6 Clay Migration 8-10 Clays, Cements, and Rock Strength . . 8-17 Clays, Drilling Mud, and CoreDamage . 8-20 Drilling Muds . . . . 8-20 Effect of Freezing . 8-21 Effect of Drying of Coreon Clay Mineral Textures and Core Permeability 8-21 Clays and Wettability . . 8-24

Clays and EOR . . . . . 8-24 Clays and Acidizing . . . 8-25 Basic Principles 8-25 in Common Minerals Found in Sandstones . 8-27 Acid Dissolution of Clays Minerals 8-27 Precipitation of Iron from Solution 8-30 Precipitation of Silica

During Mud Acid Treatments ...... 8-32 Chapter 9. CLAY MINERALS AND LOG ANALYSIS Introduction . 9-1 Porosity . 9-2

Density Log ...... 9-2 Vsh from the Simple (Unresolved) Gamma Ray Log . 9-5 Neutron Logs . . 9-8 viii

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Chapter 9 (Continued) Porosity from Combination Density-Neutron Logs . . 9-10 Sonic Logs . 9-15 Dispersed, Structural and Laminated Clay 9-15 Cementation Exponent . 9-17 Resistivity of Water-Saturated Rock . 9-20

True Resistivity . . . . . 9-21

Shaly- Log Analysis ...... 9-22 Vsh as Used in Shaly-Sand Log Analysis 9-29 Relation Between "Bound" Water, CEC, and Co . . . 9-33

Spectral Gamma Ray Logs ... 9-34

Appendix. X-RAY DIFFRACTION AND SAMPLE PREPARATION

Crystallography .. . . A-1 ...... A-1 Lattices and Unit Cells A-2

Miller Indices ...... A-5 A-6 X-Ray Methods...... Properties of X-Rays . A-6

X-Ray Diffraction . A-7 Scattering , A-7

Diffraction ...... A-8

The Bragg Law .. . . A-9 Powder Diffraction . A-11 Intensity and Geometry of Diffraction . A-17 Sample Mounting and Pretreatments A-18

Sample Mounting ...... A-18

Randomly Oriented Mounts . . . . A-18 Preferentially Oriented Mounts .. . . . A-19 Sample Pretreatments for X-Ray Diffraction . .. A-20 Cation Saturating/Air Drying . . ... A-22 Ethylene Glycol and Glycerol Solvation . . . A-22 Heating to 350°C or 550°C A-23 DMSO (Dimethylsulfoxide) Intercalation . . . A-23 Quantitative Analysis of Clay Minerals .. . A-24

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