Registros

CONTENTS

Introduction ix 1 Basics 1 1.1 Terminology 1 1.2 Basic Log Types 3 1.3 Logging Contracts 9 1.4 Preparing a Logging Programme 11 1.5 Operational Decisions 14 1.6 Coring 16 1.7 Wellsite Mud Logging 21 1.8 Testing/Production Issues 24 2 Quicklook Log Interpretation 29 2.1 Basic Quality Control 29 2.2 Identifying the Reservoir 30 2.3 Identifying the Fluid Type and Contacts 32 2.4Calculating the Porosity 34 2.5 Calculating Hydrocarbon Saturation 37 2.6 Presenting the Results 40 2.7 Pressure/Sampling 42 2.8 Permeability Determination 45 3 Full Interpretation 49 3.1 Net Sand Definition 49 3.2 Porosity Calculation 51 3.3 Archie Saturation 53 3.4 Permeability 54 4 Saturation/Height Analysis 59 4.1 Core Capillary Pressure Analysis 60 4.2 Log-Derived Functions 64

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Contents5 Advanced Log Interpretation Techniques 67 5.1 Shaly Sand Analysis 67 5.2 Carbonates 73 5.3 Multi-Mineral/Statistical Models 74 5.4 NMR Logging 76 5.5 Fuzzy Logic 85 5.6 Thin Beds 87 5.7 Thermal Decay Neutron Interpretation 93 5.8 Error Analyses 96 5.9 Borehole Corrections 101 6 Integration with Seismic 103 6.1 Synthetic Seismograms 103 6.2 Fluid Replacement Modelling 108 6.3 Acoustic/ElasticImpedance Modelling 110 7 Rock Mechanics Issues 115 8 Value Of Information 119 9 Equity Determinations 125 9.1 Basis for Equity Determination 126 9.2 Procedures/Timing for Equity Determination 127 9.3 The Role of the Petrophysicist 129 10 Production Geology Issues 137 10.1 Understanding Geological Maps 140 10.2 Basic Geological Concepts 147 11 Reservoir Engineering Issues 155 11.1 Behavior ofGases 155 11.2 Behavior of Oil/Wet Gas Reservoirs 159 11.3 Material Balance 162 11.4 Darcy’s Law 163 11.5 Well Testing 166

12 Homing-in Techniques 171 12.1 Magnetostatic Homing-in 171 12.2 Electromagnetic Homing-in 185 13 Well Deviation, Surveying, and Geosteering 193 13.1 Well Deviation 193 13.2 Surveying 195

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13.3 13.4 13.5

Geosteering 197 Horizontal Wells Drilled above aContact 203 Estimating the Productivity Index for Long Horizontal Wells 205

Appendix 1 Test Well 1 Data Sheet 207 Appendix 2 Additional Data for Full Evaluation 215 Appendix 3 Solutions to Exercises 218 Appendix 4 Additional Mathematics Theory 251 Appendix 5 Abbreviations and Acronyms 264 Appendix 6 Useful Conversion Units and Constants 268 Appendix 7 Contractor Tool Mnemonics 271 Bibliography309 About the Author 313 Acknowledgments 314 Index 315

INTRODUCTION

The purpose of this book is to provide a series of techniques which will be of real practical value to petrophysicists in their day-to-day jobs. These are based on my experience from many years working in oil companies. To this end I have concentrated wherever possible on providing one recommended technique, rather thanoffer the reader a choice of different options. The primary functions of a petrophysicist are to ensure that the right operational decisions are made during the course of drilling and testing a well—from data gathering, completion and testing—and thereafter to provide the necessary parameters to enable an accurate static and dynamic model of the reservoir to be constructed. Lying somewhere betweenOperations, Production Geology, Seismology, Production Technology and Reservoir Engineering, the petrophysicist has a key role in ensuring the success of a well, and the characterization of a reservoir. The target audience for this book are operational petrophysicists in their first few years within the discipline. It is expected that they have some knowledge of petroleum engineering and basicpetrophysics, but lack experience in operational petrophysics and advanced logging techniques. The book also may be useful for those in sister disciplines (particularly production geology and reservoir engineering) who are using the interpretations supplied by petrophysicists.

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C H A P T E R

1

BASICS

1.1 TERMINOLOGY Like most professions, petroleum engineering is beset with jargon....