HR: 1340h
AN: H33A-1380    [Abstracts]
TI: Pore-Scale Acoustic Effects on Colloid Interactions at Solid/Liquid Interfaces under Varying Physicochemical Conditions
AU: * Roberts, P M
EM: proberts@lanl.gov
AF: Los Alamos National Laboratory, PO Box 1663 MS-D443, Los Alamos, NM 87545 United States
AB: Acoustic energy can produce enhanced attachment and/or detachment of colloids at solid/liquid interfaces. This, in turn, can cause changes in colloid and fluid transport through porous media that depend strongly on the physical and chemical properties of the porous matrix, the fluid contained in the matrix pore space, and the colloids suspended in the fluid. Accumulation or release of colloids can alter the permeability of the porous medium. This can cause either good or bad effects on porous fluid-flow behavior in the Earth and geomaterials. Prior experiments using a microscopic, video image-processing system focused on a glass flow-visualization cell indicated that 0.5 to 5 MHz acoustic energy can induce attachment and detachment of sub-micron-size polystyrene microspheres at solid/liquid interfaces, using 0.1 M NaCl solution as the suspending fluid. New experiments were performed under differing initial conditions of ionic strength and solid surface properties, and at different acoustic frequencies. Initial results of these microscopic experiments will be presented. Other prior experiments showed that 50 Hz mechanical stress oscillations can mobilize trapped in-situ colloids in centimeter-size sandstone cores. A unique core-holder apparatus that mechanically strains 2.54-cm-diameter porous rock samples during constant-rate fluid flow was used for those experiments. New experiments were performed by injecting into clean core samples the same polystyrene microsphere suspensions used in the microscopic visualization experiments. Microsphere trapping in the core was induced by using a high ionic strength suspending solution. The core was then flushed with de-ionized water. This caused rapid release of the majority of trapped microspheres. Stress stimulation at 26 Hz caused additional releases of the remaining trapped microspheres at a rate approximately 4 times higher than the average background rate during water flow alone. Results of several core-scale experiments run over a range of ionic strengths will be presented.
DE: 1835 Hydrogeophysics
DE: 1859 Rocks: physical properties
DE: 1899 General or miscellaneous
DE: 4499 General or miscellaneous
SC: Hydrology [H]
MN: Fall Meeting 2005