Velocity Dispersion Caused by Pore-Pressure Equilibration in Fluid-Saturated Porous Media

Abstract

The standard Biot theory for acoustic wave propagation in fluid-saturated porous media involves a pore-fluid pressure that is averaged over many pore volumes. This approximation is quite reasonable at low frequencies and in many synthetic materials. In certain types of materials at high frequencies (e.g. rocks at ultrasonic frequencies) the assumption of uniform pore-fluid pressure is not valid. The resulting flow of pore fluid causes acoustic velocities to vary with frequency. We show how the magnitude of this dispersion can be calculated from experimental ultrasonic data.