Page 22 - Petrophysics

PREFACE TO THE SECOND EDITION

This second edition of Petrophysics has been designed to amplify the first
volume (from 8 to 10 chapters) and comply with suggestions from colleagues
and numerous readers who were generous in taking time to convey their advice.
Readers will find that the first chapter, an introduction to mineralogy, has
been considerably amplified to assist in better recognition of the multitude of
minerals and rocks. There was no noticeable change to Chapter 2 (Introduction
to Petroleum Geology), Chapter 7 (Applications of Darcy’s Law), or Chapter 10
(Fluid-Rock Interactions).
Chapter 3 (Porosity and Permeability) underwent major changes. The
following topics were added: concept of flow units, directional permeability,
correlations between horizontal and vertical permeability, averaging techniques,
Dykstra-Parsons coefficient of permeability variation, effective permeability
from cores and well test data, and several more examples. Chapter 4
(Formation Resistivity and Water Saturation) was amplified, mainly to include the
characterization and identification of flow units in shaly formations, and more
examples. Chapter 5 of the first edition was divided into two new chapters:
Chapter 5 (Capillary Pressure) and Chapter 6 (Wettability), because of the large
amount of work that has been conducted on wettability since the publication of
the first edition. Capillary pressure and wettability are, however, bound together
because much of the basis for various tests and theories of wettability and its
impact on oil recovery is based on capillary pressure behavior as a function of
fluid saturation. It seems natural, therefore, that a thorough understanding of
capillary pressure is necessary for the study of wettability.
Chapter 8 (Naturally Fractured Reservoirs) is a new chapter. Practically all
readers who contacted us suggested that we include a more detailed discussion
of the petrophysical aspects of naturally fractured rocks. The main topics
covered in this chapter are: geological and engineering classifications of natural
fractures, indicators of natural fractures, determination of fracture porosity
and permeability, fracture intensity index, porosity partitioning coefficient, and
effect of fracture shape on permeability. A new concept of hydraulic radius of
fracture is introduced in this chapter. Methods for determining the fracture
storage capacity and inter-porosity from well test data are briefly discussed.
Several important topics were added to Chapter 9 (Effect of Stress on
Reservoir Rock Properties): the effect of change in the stress field due to

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