HR: 1330h
AN: H12A-0962    [PDF]
TI: Capillary-Physics Mechanism of Elastic-Wave Mobilization of Residual Oil
AU: * Beresnev, I A
EM: beresnev@iastate.edu
AF: Department of Geological and Atmospheric Sciences, Iowa State University, 253 Science I, Ames, IA 50011-3212 United States
AU: Pennington, W D
EM: wayne@mtu.edu
AF: Department of Geological Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 United States
AU: Turpening, R M
EM: roger@mtu.edu
AF: Department of Geological Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 United States
AB: Much attention has been given to the possibility of vibratory mobilization of residual oil as a method of enhanced recovery. The common features of the relevant applications have nonetheless been inconsistency in the results of field tests and the lack of understanding of a physical mechanism that would explain variable experiences. Such a mechanism can be found in the physics of capillary trapping of oil ganglia, driven through the pore channels by an external pressure gradient. Entrapping of ganglia occurs due to the capillary pressure building on the downstream meniscus entering a narrow pore throat. The resulting internal-pressure imbalance acts against the external gradient, which needs to exceed a certain threshold to carry the ganglion through. The ganglion flow thus exhibits the properties of the Bingham (yield-stress) flow, not the Darcy flow. The application of vibrations is equivalent to the addition of an oscillatory forcing to the constant gradient. When this extra forcing acts along the gradient, an instant "unplugging" occurs, while, when the vibration reverses direction, the flow is plugged. This asymmetry results in an average non-zero flow over one period of vibration, which explains the mobilization effect. The minimum-amplitude and maximum-frequency thresholds apply for the mobilization to occur. When the vibration amplitude exceeds a certain "saturation" level, the flow returns to the Darcy regime. The criterion of the mobilization of a particular ganglion involves the parameters of both the medium (pore geometry, interfacial and wetting properties, fluid viscosity) and the oscillatory field (amplitude and frequency). The medium parameters vary widely under natural conditions. It follows that an elastic wave with a given amplitude and frequency will {\it always} produce a certain mobilization effect, mobilizing some ganglia and leaving others intact. The exact macroscopic effect is hard to predict, as it will represent a response of the populations of ganglia with unknown parameter distributions. The variability of responses to vibratory stimulation should thus be expected.
DE: 1894 Instruments and techniques
DE: 1899 General or miscellaneous
DE: 5114 Permeability and porosity
DE: 5139 Transport properties
SC: Hydrology [H]
MN: 2003 Fall Meeting