Numerical Simulation of Improved Heavy Oil Recovery by Low-Salinity Water Injection and Polymer Flooding

Abstract

Abstract As heavy oil resources are making an ever-increasing contribution to the energy supply of the world, maximizing recovery from these wreservoirs has attracted significant attention in recent years. Leveraging low salinity waterflooding and polymer flooding to improve heavy oil recovery will be the focus of this paper. While low salinity waterflooding performance in light (conventional) oil reservoirs has been investigated extensively, it has not been applied in heavy oil systems. Published literature recorded higher oil recovery by injection of low salinity water. One major component among several mechanisms of this increase in oil recovery is due to the lower residual oil saturation (Sorw) by wettability alteration. Therefore, published data was used to produce a correlation between Sorw (high salinity water) and Sorw (low salinity water). A sector model with 36,000 grid cells was used to evaluate the performance of several injection scenarios involving low salinity water and polymer under the conditions of a heavy oil reservoir at the depth of 3,000 ft with oil viscosity of 80 centipoise (20° API). The thickness of the reservoir is less than 100 ft. The simulated results showed that low salinity waterflooding could increase the estimated ultimate recovery by approximately 5% of original oil in place (OOIP) while the polymer flood provided a similar increase with better efficiency. Subsequent simulations that combine both low salinity waterflooding and polymer resulted in an additional oil recovery of 7.5% to 10% of OOIP. The results of this study show significant potential for enhancing heavy oil recovery by low salinity waterflooding augmented by polymer injection and multilateral horizontal wells. The commercial viability of such methods to improve heavy oil recovery would make a significant step towards increasing the recovery factor from heavy oil and viscous oil reservoirs. Subsequently, the results would need to be validated by laboratory experiments to establish clear correlation between relative permeability end points with both viscosity and water salinity on heavy oil systems.