This book presents a comprehensive treatment of the elastic volumetric response of sandstones to variations in stress. The theory and data presented apply to the deformations that occur, for example, due to withdrawal of fluid from a reservoir, or due to the redistribution of stresses caused by the drilling of a borehole. Deformations that occur over geologic time scales are in general excluded, since such processes involve chemical and thermal effects in addition to purely mechanical deformation. Note that while the data presented to illustrate the principles discussed in the book are exclusively for consolidated sandstones, most of the theoretical relationships, bounds, etc. that are discussed are applicable to all rock-fluid systems.Part One establishes a general framework for the study of the volumetric response of sandstones to applied stresses. Chapter 1 discusses the various compressibility coefficients that can be defined for porous rocks. Relationships between these compressibilities are discussed in Chapter 2, and bounds on the numerical values of the compressibilities are discussed in Chapter 3. Chapter 4 treats the effective stress coefficients, which describe the relative effects of pore pressure and confining pressure. Chapter 5 covers the integrated stress-strain relationships for sandstones, in a fully nonlinear context. Undrained compression and induced pore pressures are treated in Chapter 6. Chapter 7 gives a brief introduction to the theory of poroelasticity, in effect extending the discussion in the previous chapters to situations involving deviatoric stresses.


Part Two presents, for the first time in book fomi, a detailed discussion of the relationship between compressibility and pore structure. Chapter 8 discusses mathematical models of tubular pores, Chapter 9 treats “crack-like’’ models of imperfectly bonded grain contacts, and Chapter 10 covers the modeling of pores as spheroids. Chapter 11 discusses the effect of pore shape on the overall effective bulk and shear moduli. Methods for relating the stress-strain behavior of a sandstone to the distribution f the aspect ratios of its pores are described in Chapter 12. Part Three (Chapter 13) presents brief discussions of experimental methods used to measure compressibility in the laboratory.