Study of polymer-enhanced emulsion flooding to improve viscous oil recovery in waterflooded heavy oil reservoirs

Emulsion flooding is an effective enhanced oil recovery (EOR) process for waterflooded heavy oil reservoirs, which is not suitable for the application of thermal recovery methods because of economic issues or technical impediments. This study demonstrated the experimental investigation of polymer-enhanced emulsion to improve the viscous oil recovery in waterflooded heavy oil reservoirs. It was indicated in the emulsion stability and rheology studies that the polymer HPAM not only acted as a thickener to slow down the rate of creaming by increasing the water viscosity, but also enhanced the strength of O/W interface by increasing interfacial shear viscosity, resulting in a significant increase of the stability and bulk viscosity of emulsion system. The results of sandpack flooding tests showed that an incremental oil recovery of more than 30% of original oil in place (OOIP) over water flooding could be obtained by polymer-enhanced emulsion flooding for heavy oil with the viscosity of 350 mPa s at 50 degrees C. The micromodel flooding studies indicated that the EOR mechanisms of polymer-enhanced emulsion were attributed to the reduction in mobility ratio due to higher emulsion viscosity, resulting in dramatically improvement of sweep efficiency. Besides, biodiesel could reduce the heavy oil viscosity to improve the mobility of heavy oil, and the surfactant could emulsify the heavy oil in water to form O/W emulsions, thereby improving the displacement efficiency. The results of these studies showed that polymer-enhanced emulsion flooding is a promising process to improve oil recovery in waterflooded heavy oil reservoirs.