Effects of Oil Viscosity on the Plugging Performance of Oil-in-Water Emulsion in Porous Media

Oil-in-water (O/W) emulsion is an effective plugging agent for improving fluid mobility conformance. Most studies to date have attributed the plugging mechanism solely to the "Jamin effect". In this work, we investigate the influence of oil phase viscosity on the plugging performance of O/W emulsions in porous media. Sandpack flow tests were conducted to quantitatively evaluate such effects. Systematic data of pressure drop versus oil viscosity under varied sandpack permeabilities and flow rates were reported. The oil viscosities of emulsions used in this study ranged from 9.4 to 496.0 cP. During flow tests, potential interference from interfacial tension (IFT) and droplet size was eliminated. The results show that oil viscosity of O/W emulsion considerably affects pressure drop across the sandpack. Frictional resistance increases as oil viscosity increases, but the rate of increment tapers down significantly. The plugging effect due to oil viscosity is dependent on sandpack permeability and emulsion injection rate. The effective viscosity of the emulsions increases as oil viscosity increases and decreases as the injection rate increases. The droplet-wall friction at pore throat, the slipping behavior, and the change of flow path are considered essential mechanisms for such results.