Carbonate Reservoir Characterization

Carbonate Reservoir Characterization

(Parte 1 de 6)

F. Jerry Lucia Carbonate Reservoir Characterization

F. Jerry Lucia

Carbonate

Reservoir

Characterization An Integrated Approach

Second Edition

With 233 Figures

F.JERRY LUCIA Bureau of Economic Geology University Station Box X Austin, Texas 78713 USA

E-Mail: jerry.lucia@beg.utexas.edu

Library of Congress Control Number: 2007934760

ISBN 978-3-540-72740-8 Springer Berlin Heidelberg New York ISBN 978-3-540-63782-0 (first edition) Springer Berlin Heidelberg New York

This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag. Violations are liable to prosecution under the German Copyright Law.

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The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.

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Preface

voir models

This book is intended for the use of geologist, geophysists, petrophysists, and engineers interested in building geologic models that can be converted into realistic reservoir flow models of carbonate reservoirs. The first edition of this book was focused on methods and approaches for constructing improved carbonate reservoir models. In this second edition these methods are enlarged based on research results since the first edition was published. Each chapter contains new information, particularly in the area of wireline logs and geostatistics. Importantly, several new field studies are included that illustrate the application of these methods in building reser-

As in the first edition, the integration of geological and engineering data is at the center of the approach described in this edition. The fundamental link between geologic models and engineering fluid-flow models is the relationship between petrophysical properties and rock fabrics. Pore geometries control the flow properties and geologic history, as observed in rock fabrics, controls the pore geometries. Therefore, it is the study of rock fabrics that integrates geological and engineering data.

myself in carbonates, and Robert Sneider in clastics

Not surprisingly, the approach is referred to as the “rock-fabric method.” This method is an outgrowth of the published works of G.E. Archie (Gus), and the reader is encouraged to read the few reference to his work presented at the end of this Preface. The author is well acquainted with his work because Gus hired the author into Shell Oil in 1954 and work for him at Shell Development’s research laboratory in Houston for a number of years. Gus pioneered the idea of relating petrophysical properties to rock fabrics, an idea that was further developed by Ray Murray and

In this book I present a current picture of how this method can be applied in limestone, dolostone, and touching-vug reservoirs. The chapters have been reorganized to accommodate the research advances in the past nine years. Reservoir characterization is first and foremost concerned with developing 3D images of petrophysical properties suitable for input into fluid-flow computer simulators. Therefore, as in the first edition, the first chapter is a review of petrophysical data and how the data are obtained. The second chapter discusses relationships between rock fabric, porosity,

VI Preface permeability, and saturation, and is the soul of the rock fabric method for reservoir characterization. Chapter 3 discusses methods for calculating interparticle porosity, permeability, and initial water saturation using the rock-fabric approach, permeability transforms, and capillary pressure models. New in this chapter is a thorough discussion of using wireline logs to identify geologic and rock-fabric facies. Chapter 4 discusses using sequence stratigraphy and depositional models to distribute rock fabrics in 3D space. Diagenesis, as well as deposition, is a major contributor to poresize distribution and an overview of limestone diagenesis, dolomitization, and meteoric diagenesis is included in Chapters 6, 7, and 8. Chapter 5 is a new chapter that focuses on distributing petrophysical properties in 3D space using geostatistical methods constrained by rock fabric flow layers and sequence stratigraphy. Examples of how this approach is used to describe limestone reservoirs are presented in Chapter 6, to describe dolostone reservoirs in Chapter 7, and to describe touching-vug reservoirs in Chapter 8.

Much of the research presented in this book was done by the author and his colleagues over the past 20 years at the Bureau of Economic Geology, the University of Texas at Austin, which has recently becoming part of the new Jackson School of Geoscience. I am indebted to my fellow geologists, Charlie Kerans and Steve Ruppel, for allowing me to publish the results of some of their outcrop and subsurface studies. In am also indebted to my fellow engineers James Jennings and Fred Wang for their contributions to this book. I am particularly indebted to James Jennings for his significant contribution to my understanding of the petrophysical variability in carbonates and to the use geostatistics to distribute and upscale petrophysical properties. My colleagues and I have worked together as an integrated team to develop the reservoir characterization methods presented in this book.

The research was funded by the sponsors of the Reservoir Characterization Research Laboratory for Carbonate Reservoir (RCRL) at the Bureau of Economic Geology. A number of companies have been sponsors for most of the 16 years the RCRL has been in existance; Chevron/Texaco, Exxon/Mobil, BP, Shell/Production Development Oman, Altura/Oxy Permian, Marathon, and Saudi Aramco. Other companies that have supported the RCRL include Conoco/Phillips, Anadarko, Statoil, ENI, TOTAL, Norsk Hydro, Kinder Morgan, and Pioneer.

Preface VII

This book would never have been published without the able assistance of my editor, Amanda Masterson. If there are errors in this book it is because I failed to make the corrections she highlighted.

Austin, TexasF. Jerry Lucia

May, 2007

References

Archie GE. 1952 Classification of carbonate reservoir rocks and petrophysical considerations. AAPG Bull 36, 2:278-298

Archie GE 1942 The electrical resistivity log as an aid in determining some reservoir characteristics. Trans AIME, 146:54-62

Archie GE 1950 Introduction to petrophysics of reservoir rocks. AAPG Bull 34, 5:943-961

Contents

Chapter 1 Petrophysical Rock Properties

1.2 Porosity ………………………………………………………1

1.1 Introduction ……………………………………………………… 1 1.3 Permeability ……………………………………………………… 6 1.4 Pore Size and Fluid Saturation …………………………………… 10 1.5 Relative Permeability …………………………………………….. 20 1.6 Summary …………………………………………………………. 25 References ……………………………………………………………. 26

Chapter 2 Rock-Fabric Classification

2.2 Pore Space Terminology and Classification ……………………30
2.3 Rock Fabric/Petrophysical Classification ………………………3

2.1 Introduction ………………………………………………………. 29 2.3.1 Classification of Interparticle Pore Space …………………. 3 2.3.2 Classification of Vuggy Pore Space ………………………. 36

Touching-Vug Pore Space ………………………………38

Separate-Vug Pore Space …………………………………. 37 2.4 Rock-Fabric/Petrophysical Relationships ……………………….. 38 2.4.1 Interparticle Porosity/Permeability Relationships ………… 38

Dolostone Rock Fabrics …………………………………43
Permeability Estimation …………………………………48
2.4.3 Rock-Fabric/Petrophysical Classes ………………………53
2.4.5 Petrophysics of Touching-Vug Pore Space ………………59

Limestone Rock Fabrics ………………………………….. 38 Limestone and Dolomite Comparison ……………………. 46 2.4.2 Rock-Fabric/Porosity/Water Saturation Relationships ……. 50 2.4.4 Petrophysics of Separate-Vug Pore Space ………………… 5 2.5 Summary …………………………………………………………. 62 References ……………………………………………………………. 65

X Contents

Chapter 3 Wireline Logs

3.4.5 Lithology …………………………………………………82
3.4.6 Acoustic Logs ……………………………………………84
3.4.7 Resistivity/Induction Logs ………………………………91
3.4.8 Formation Imaging Logs …………………………………102
3.5 Permeability from Wireline Logs ………………………………104

3.1 Introduction ………………………………………………………. 69 3.2 Core Description …………………………………………………. 70 3.3 Core Analysis …………………………………………………….. 71 3.4 Core/Log Calibration …………………………………………….. 71 3.4.1 Procedures for Core-Log Calibration ……………………… 72 3.4.2 Gamma-Ray Logs …………………………………………. 73 3.4.3 Borehole Environment …………………………………….. 76 3.4.4 Neutron-Density Cross-Plot Porosity ……………………… 76 3.6 Initial Water Saturation ………………………………………….. 105 3.7 Summary ………………………………………………………… 106 References …………………………………………………………… 109

Chapter 4 Depositional Textures & Petrophysics

4.1 Introduction ………………………………………………………. 1 4.2 Properties of Carbonate Sediments ………………………………. 112 4.3 Sequence Stratigraphic Framework ……………………………… 119 4.3.1 High-Frequency Cycles …………………………………… 122 4.3.2 High-Frequency Sequence ………………………………… 129 4.4 Example ………………………………………………………….. 133 4.5 Summary …………………………………………………………. 138 References ……………………………………………………………. 139

Chapter 5 Reservoir Models for Input into Flow Simulators

5.2 Geostatistical Methods …………………………………………146
5.4 Lawyer Canyon Reservoir Analog Study ………………………160
5.4.1 Introduction ………………………………………………160
5.4.2 Model Construction ………………………………………160

5.1 Introduction ……………………………………………………… 143 5.2.1 Variography ……………………………………………….. 146 5.2.2 Conditional Simulation ……………………………………. 148 5.3 Scales of Variability and Average Properties ……………………. 149 5.4.3 Rock-Fabric Flow Units …………………………………… 162 5.4.4 Fluid Flow Experiments …………………………………… 164

Contents XI

5.5 Work Flow for Construction of the Reservoir Model …………… 166 5.6 Summary…………………………………………………………. 176 References …………………………………………………………… 177

Chapter 6 Limestone Reservoirs

6.2.2 Compaction ………………………………………………187
6.3.3 Moldic Grainstone, Permian, Guadalupe Mountains, USA202

6.1 Introduction ……………………………………………………… 181 6.2 Cementation/Compaction/Selective Dissolution ………………… 184 6.2.1 Calcium Carbonate Cementation ………………………….. 184 6.2.3 Selective Dissolution ……………………………………… 190 6.2.4 Effects on Petrophysical Properties Distribution ………….. 192 6.3 Limestone Reservoir Examples ………………………………….. 194 6.3.1 Mississippian Chester Field, Oklahoma, USA …………….. 194 6.3.2 Tubarao (Cretaceous) Field, Offshore Brazil ……………… 197 6.3.4 Idd el Shargi Cretaceous Reservoir, Qatar, Middle East …. 202 6.3.5 Upper Devonian Reef Buildups, Alberta, Canada ………… 210 References …………………………………………………………… 213

Chapter 7 Dolostone Reservoirs

7.3.1 Calcitization of Anhydrite/Gypsum………………………236
7.4.2 Andrews South Devonian Field, West Texas ……………240

7.1 Introduction ………………………………………………………. 217 7.2 Dolomitization …………………………………………………… 218 7.2.1 Hydrologic Models ………………………………………… 218 7.2.2 Dolomitization and Petrophysical Properties ……………… 220 7.2.3 Distribution of Dolostone ………………………………….. 231 7.2.4 Calcitization of Dolomite ………………………………….. 233 7.3 Evaporite Mineralization ………………………………………… 233 7.4 Field Examples – Dolostone/Limestone Reservoirs …………….. 237 7.4.1 Red River Reservoirs, Montana and North Dakota ……….. 238 7.4.3 Haradh Section of Ghawar Field…………………………… 243

Vertical succession of depositional textures ……………… 243 Rock fabric description and petrophysical properties …….. 243 Calibration of wireline logs ……………………………….. 245 Calculation of vertical profiles of petrophysical properties . 248 Reservoir model construction …………………………….. 248 7.5 Field Examples - Dolostone Reservoirs …………………………. 249 7.5.1 Seminole San Andres Unit, Gaines County, Texas ……….. 250 Vertical succession of depositional textures ……………… 251

XII Contents

Reservoir model construction ……………………………261

Rock-fabric descriptions and petrophysical properties …… 252 Calibration of wireline logs ………………………………. 256 Calculating vertical profiles of petrophysical properties …. 259 Flow simulation model ……………………………………. 264 7.5.2 South Wasson Clear Fork …………………………………. 266

Vertical succession of depositional textures ……………… 266 Rock-fabric descriptions and petrophysical properties …… 269 Calibration of wireline logs ……………………………….. 272 Calculating vertical profiles ………………………………. 275 Reservoir model construction …………………………….. 276 Flow simulation model ……………………………………. 278 7.5.3 Fullerton Clear Fork Reservoir ……………………………. 280

Full field model construction ……………………………293

Vertical succession of depositional textures ……………… 280 Rock fabric descriptions and petrophysical properties …… 286 Calibration of wireline logs ……………………………….. 288 Calculating vertical profiles of petrophysical properties …. 291 Flow simulation model …………………………………… 294 References …………………………………………………………… 296

Chapter 8 Touching-Vug Reservoirs

8.1 Introduction ……………………………………………………… 301 8.2 Small-scale dissolution, collapse, and microfracturing ………….. 303 8.2.1 Effects on Petrophysical Properties ……………………….. 303 8.2.2 Small-scale touching vug reservoirs ………………………. 304

8.3 Large-scale dissolution, collapse, and fracturing ………………309
San Andres Fields, West Texas …………………………318
Elk Basin Mississippian Reservoir ………………………321

South Cowden Grayburg Reservoir ………………………. 305 8.3.1 Effects on Petrophysical Properties Distribution ………….. 315 8.3.2 Large-scale touching-vug reservoirs ………………………. 317 Ellenburger Lower Ordovician Fields …………………….. 323 Silurian Reef Fields ……………………………………….. 327 References …………………………………………………………… 329

Subject Index ………………………………………………………… 3

Chapter 2 Rock-Fabric Classification

2.1 Introduction

The goal of reservoir characterization is to describe the spatial distribution of petrophysical parameters such as porosity, permeability, and saturation. In Chapter 1 we showed that porosity, permeability, and fluid saturations are linked through pore size. In this chapter we will expand simple pore size to pore-size distribution, that is, the spatial distribution of pore sizes within the rock, and show how pore-size distribution can be linked to rock fabrics. Wireline logs, core analyses, production data, pressure buildups, and tracer tests provide quantitative measurements of petrophysical parameters in the vicinity of the wellbore, but they generally provide only one-dimensional spatial information. Therefore, wellbore data must be integrated with geologic models to display the petrophysical properties in three-dimensional space. Studies that relate rock fabric to pore-size distribution, and thus to petrophysical properties, are key to quantification of geologic models in numerical terms for input into computer simulators (Fig. 1).

Fig. 2.1. Integration of spatial geologic data with numerical engineering data through rock-fabric studies

30 Chapter 2 Rock-Fabric Classification

Geologic models are generally based on observations that are interpreted in terms of depositional models and sequences. In the subsurface, cores, wireline logs, and seismic data are the main sources of information for these interpretations. Engineering models are based on wireline log calculations and average rock properties from core analyses. Numerical engineering data and interpretive geologic data are linked by rock fabrics because the pore structure is fundamental to petrophysical properties, and the pore structure is the result of spatially distributed depositional and diagenetic processes.

The purpose of this chapter is to define important geologic parameters to be described and mapped to allow accurate petrophysical quantification of carbonate geologic models by (1) describing the relationship between carbonate rock fabrics and petrophysical properties and (2) presenting a generic petrophysical classification of carbonate pore space.

2.2 Pore Space Terminology and Classification

related to these textures

Pore space must be defined and classified in terms of rock fabrics and petrophysical properties in order to integrate geological and engineering information. Archie (1952) made the first attempt at relating rock fabrics to petrophysical rock properties in carbonate rocks. The Archie classification focuses on estimating porosity but is also useful for approximating permeability and capillary properties. Archie (1952) recognized that not all the pore space can be observed using a 10 power microscope and that the surface texture of the broken rock reflected the amount of matrix porosity. Therefore, pore space is divided into matrix and visible porosity (Fig. 2). Chalky texture indicates a matrix porosity of about 15 percent, sucrosic texture indicates a matrix porosity of about 7 percent, and compact texture indicates matrix porosity of about 2 percent. Visible pore space is described according to pore size; A for no visible pore space and B, C, and D for increasing pore sizes from pinpoint to larger than cutting size. Porosity/permeability trends and capillary pressure characteristics are also

(Parte 1 de 6)

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