Page 12 - Reservoir Geomechanics

Preface

This book has its origin in an interdisciplinary graduate class that I’ve taught at Stan-
ford University for a number of years and a corresponding short course given in the
petroleum industry. As befitting the subject matter, the students in the courses represent
avariety of disciplines – reservoir engineers and geologists, drilling engineers and geo-
physicists. In this book, as in the courses, I strive to communicate key concepts from
diverse disciplines that, when used in a coordinated way, make it possible to develop
a comprehensive geomechanical model of a reservoir and the formations above it. I
then go on to illustrate how to put such a model to practical use. To accomplish this,
the book is divided into three major sections: The first part of the book (Chapters 1–5)
addresses basic principles related to the state of stress and pore pressure at depth, the
various constitutive laws commonly used to describe rock deformation and rock failure
in compression, tension and shear. The second part of the book (Chapters 6–9) addresses
the principles of wellbore failure and techniques for measuring stress orientation and
magnitude in deep wells of any orientation. The techniques presented in these chapters
have proven to be reliable in a diversity of geological environments. The third part of
the book considers applications of the principles presented in the first part and tech-
niques presented in the second. Hence, Chapters 10–12 address problems of wellbore
stability, fluid flow associated with fractures and faults and the effects of depletion on
both a reservoir and the surrounding formations.
Throughout the book, I present concepts, techniques and investigations developed
over the past 30 years with a number of talented colleagues. Mary Lou Zoback (formerly
with the U.S. Geological Survey) and I developed the methodologies for synthesis of
various types of data that indicate current stress orientations and relative magnitudes in
the earth’s crust. As summarized in Chapter 1, Mary Lou and I demonstrated that it was
possible to develop comprehensive maps of stress orientation and relative magnitude
and interpret the current state of crustal stress in terms of geologic processes that are
active today. The quality ranking system we developed for application to the state of
stress in the conterminous U.S. (and later North America) is presented in Chapter 6.It
has been used as the basis for almost all stress mapping endeavors carried out over the
past 20 years and provided the basis for the compilation of stress at a global scale (the
World Stress Map project), led by Mary Lou.
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