Rock-physics developments in seismic exploration: A personal 50-year perspective

Abstract

I present an historical overview of the major developments in rock physics over the past half-century. Key developments are described for both modeling and laboratory experiments and how they have been applied in seismic exploration, reservoir characterization, and monitoring. In particular, I chronicle the development of laboratory methods for determining the velocity and attenuation of elastic waves in rock samples at sonic and ultrasonic frequencies. This is followed by a description of the validity of theories originally developed by Gassmann and Biot in the 1950s and employed for describing the propagation of elastic waves in fluid-saturated porous media. I outline problems and solutions in the use of ultrasonic measurements to predict velocities and attenuation at seismic frequencies. Field and laboratory studies are described in which a range of frequencies — seismic through sonic and ultrasonic — was covered and successfully modeled. I describe procedures developed during the 1950s and 1960s for interpreting laboratory measurements in terms of pore structure and degree of saturation, based on self-consistent and scattering theories. Laboratory equipment used for determining the elastic properties of anisotropic materials is described along with a discussion of the results obtained, including the correlation between both fluid permeability and prediction of in situ state of stress with the degree of shear-wave splitting. Finally, I discuss the application of rock-physics developments to reservoir characterization and monitoring, in particular to time-lapse seismic monitoring.