Tarek Hamida

Investigations on Capillary and Viscous Displacement Under Ultrasonic Waves

In this paper, the influence of ultrasonic waves on capillary and viscous displacement of oil in porous media was investigated. Capillary (spontaneous) imbibition experiments were conducted using various fluid pairs such as air-water, mineral oil-brine, mineral oil-surfactant solution, kerosene-surfactant solution, and mineral oil-polymer solution. Berea sandstone and Indiana limestone cores were used as the matrix. Oil saturated cores were immersed into the aqueous phase and subjected to high intensity ultrasound from a specially designed ultrasonic chamber. The resulting recovery was recorded against time, and compared to a control experiment without ultrasound. A substantial increase in ultimate recovery was observed for most of the fluid pairs, with some improvements in recovery rate. To further investigate whether ultrasound induces a perturbation at the liquid-liquid interface of immiscible fluids, a series of Hele-Shaw type experiments were run. The resulting fingering pattern was strongly dependent on the interfacial tension of the fluid pair, and the injection rate. Ultrasound stabilized the fluid-fluid front of high interfacial tension fluid pairs, but generated larger instabilities when interfacial tension was low.

Immiscible displacement of oil by water in consolidated porous media due to capillary imbibition under ultrasonic waves

Numerous studies done in the last four decades have demonstrated that acoustic stimulation may enhance recovery in oil reservoirs. This technology is not only technically feasible, but also serves as an economical, environmentally friendly alternative to currently accepted enhanced oil recovery (EOR) method. It requires low capital expenditure, and yields almost immediate improvement without any additional EOR agents. Despite a vast body of empirical and theoretical support, this method lacks sufficient understanding to make meaningful and consistent engineering predictions. This is in part due to the complex nature of the physical processes involved, as well as due to a shortage of fundamental/experimental research. Much of what the authors believe is happening within acoustically stimulated porous media is speculative and theoretical. This paper focuses on the effects of ultrasound on the interfacial forces between immiscible fluids. Capillary (spontaneous) imbibition of an aqueous phase into oil (or air)-saturated Berea sandstone and Indiana limestone samples experiments were conducted. Solutions of water, brine (15,000 and 150,000 ppm NaCl), anionic surfactant (sodium dodecyl diphenyloxide disulfonate), nonionic surfactant (alcohol ethoxylate) and polymer (xanthan gum) were prepared as the aqueous phase. Both counter-current and co-current geometries were tested. Due to the intrinsically unforced, gentle nature of the process, and their strong dependence on wettability, interfacial tension, viscosity and density, such experiments provide valuable insight into some of the governing mechanisms behind ultrasonic stimulation.