Influence of the Gravity Override on the Optimal Gas Flooding Strategies

Water-alternating-gas injection into oil reservoirs, i.e., the gas method of enhancd oil recovery that supposes water and carbon dioxide injection in the reservoir with the aim to increase the oil recovery is investigated. The use of such stimulation is complicated by the possibility of gravity override that leads to non-uniform sweep efficiency. Dimensionless parameters which characterize phase override are determined from the system of equations that describe the flow of water and two-phase hydrocarbon mixture. It is shown that the efficiency of water-alternating-gas injection depends on three similarity parameters. The parametric investigation of the optimum strategies of water and carbon dioxide injection is carried out when one of the dimensionless similarity parameters varies. The diagram of optimal strategies of water-alternating-gas injection is constructed. The optimum completion intervals for the injection and producing well are investigated for various values of the taken parameter.