Designing a Simultaneous Water Alternating Gas Process for Optimizing Oil Recovery

Abstract

Abstract Recently there has been an increasing interest in simultaneous water-alternating-gas (SWAG) in oil recovery operations. This method involves the simultaneous injection of water at the top of the reservoir formation and injecting gas at the bottom of the formation. The difference in water and gas densities will provide a sweeping mechanism in which water tends to sweep hydrocarbons downward and the gas tends to sweep the hydrocarbons upward. It is expected that the two displacement mechanisms will work on establishing a flood front, which will increase the sweep efficiency and thus the oil recovery. This study investigated the performance of SWAG in oil recovery operations. A three-dimensional finite-difference black oil reservoir simulator has been used to determine the reservoir management strategies in order to optimize the oil recovery using SWAG injection technique. A specific strategy that was studied includes the use of horizontal injectors in conjunction with vertical producers. This well configuration has been shown to yield the best oil recovery compared to other well configurations. The management strategies involved studying different design parameters to maximize the recovery performance. Such parameters include; mobility ratio between oil and water phases, viscosity ratio between gas and oil phases, location of the water and the gas injectors, and injection rates of water and gas. Results showed the investigated parameters are critical in the success of the proposed injection SWAG scheme. The study provides the conditions under which this SWAG injection technique may yield higher recovery performance.