ATTENUATION AND DISPERSION OF COMPRESSIONAL WAVES IN FLUID-FILLED POROUS ROCKS WITH PARTIAL GAS SATURATION (WHITE MODEL) .1. BIOT THEORY

An exact theory of attenuation and dispersion of seismic waves in porous rocks containing spherical gas pockets (White model) is presented using the coupled equations of motion given by Biot. Assumptions made are 1) the acoustic wavelength is long with respect to the distance between gas pockets and their size, and 2) the gas pockets do not interact. Thus, the present theory essentially is quite similar to that proposed by White (1975), but the problem of the radially oscillating gas pocket is solved in a more rigorous manner by means of Biot's theory (1962). The solid-fluid coupling is automatically included, and the model is solved as a boundary value problem requiring all radial stresses and displacements to be continuous at the gas-brine interface. Thus, we do not require any assumed fluid-pressure discontinuity at the gas-water contact, such as the one employed by White (1975). We have also presented an analysis of all of the field variables in terms of Biot's type I (the classical compressional) wave and type II (the diffusion) wave. Our quantitative results are presented in Dutta and Ode (1979, see above). -Authors