Permeability and borehole Stoneley waves; comparison between experiment and theory

Abstract

Abstract We performed laboratory experiments to evaluate theoretical models of borehole Stoneley wave propagation in permeable materials. A Berea sandstone and synthetic samples made of cemented glass beads were saturated with silicone oils. We measured both velocity and attenuation over a frequency band from 10 kHz to 90 kHz. Our theoretical modeling incorporated Biot theory and Deresiewicz-Skalak boundary conditions into a cylindrical geometry and included frequency-dependent permeability. By varying the viscosity of the saturating pore fluid, we were able to study both low-frequency and high-frequency regions of Biot theory, as well as the intermediate transition zone. In both low-frequency and high-frequency regions of the theory, we obtained excellent agreement between experimental observations and theoretical predictions. Velocity and attenuation (1/Q) are frequency-dependent, especially at low frequencies. Also at low frequencies, velocity decreases and attenuation increases with increasing fluid mobility (permeability/viscosity). More complicated behavior is observed at high frequencies. These results support recent observations from the oil field suggesting that Stoneley wave velocity and attenuation may be indicative of formation permeability.