Low-frequency acoustic stimulation of fluid flow in porous media

Abstract

Historical Russian and U.S. research has indicated that acoustic or elastic (seismic) waves transmitted into oil reservoirs at frequencies of 1–500 Hz can increase oil production rates. Results from prior field tests on reservoir formations and laboratory experiments on porous rock samples have been largely inconclusive. The underlying physical mechanisms are still speculative. Comprehensive experimental laboratory and theoretical data on the interactions between acoustic waves and fluid flow in porous media are required before the phenomenon can be exploited reliably for enhanced oil recovery or other applications such as groundwater remediation. A specialized laboratory facility was constructed to characterize effects that low-frequency stress oscillations have on permeability and two-phase fluid flow in cylindrical rock and sand samples. Applied mechanical axial stress, axial and radial strains, permeability changes, fluid production rates, and dynamic elastic moduli are all measured during excitation of the samples. Positive results were observed for enhanced permeability, mobilization of trapped immiscible fluid phases, and increased production rates for sandstone-brine-decane and sand-water-trichloroethylene systems. These results will be presented along with discussions of possible physical mechanisms involved. [Work supported by the U.S. Department of Energy, Office of Fossil Energy.]