Effect of pore fluid viscosity on the velocities of acoustic waves in porous rocks

Abstract

Compressional and shear velocities of acoustic waves propagating in porous rocks saturated with viscous fluids were measured both in the kHz and MHz frequency range. The experimental results of the velocities were plotted as a function of pore fluid viscosity ranging from 1 to 1010 centipoise. It was shown that the measured velocities increased with increasing pore fluid viscosity in the kHz frequency range, while in the MHz range, the pore fluid viscosity did not have much effect on the acoustic wave velocities. The experimental results were also discussed in terms of theories of wave propagating in viscous fluids and in the saturated porous solids. Applications of the results to oil production and exploration, as well as to the low velocity zone in the earth, were also presented.