Oil phase displacement by acoustic streaming in a reservoir-on-a-chip

Abstract

This article presents a reservoir-on-a-chip study of acoustic streaming as an enhanced oil recovery mechanism. Microfluidic devices with different porosities are fabricated using photolithography to serve as reservoir-on-a-chip micromodels. We use microparticle image velocimetry to characterize acoustic streaming-induced pumping as a function of frequency and amplitude. A scaling model applied to the velocity distribution is used to construct a state diagram that connects acoustic pressure to field frequency and amplitude. Optical video fluorescence microscopy is used to track the invasion of a water phase through the oil-saturated porous micromodel. Based on these measurements, we calculate the Blake number as a function of frequency to show that our system exhibits a narrow band dynamic response consistent with a system operating near resonance. Our observations are compared to a general model for Blake number as a function of frequency, porosity and voltage amplitude that was derived from a force balance model of the micromodel undergoing forced oscillation. The results from this paper are broadly applicable to systems beyond enhanced oil recovery, including separations, bio-analytical instruments, additive manufacturing and flow control.