Techno-economical optimization of water-alternating-CO2/dimethyl ether process for enhanced oil recovery

Abstract

The use of CO2 to improve oil recovery has the disadvantage of reduced sweep efficiency due to the large difference in density and viscosity between oil and CO2. Overcoming these drawbacks, the use of dimethyl ether (DME) is known to be more effective than CO2 in improving oil recovery. In this study, a CO2-DME mixed solvent, is thoroughly investigated by developing a compositional model. The oil recovery of a CO2-DME mixed solvent has been examined in terms of sweep efficiency and displacement efficiency by comparing CO2-water-alternating-gas (WAG) and CO2-DME WAG. According to the results from compositional simulation, the highest DME content investigated resulted in a 66.4% lower viscous gravity number and a 26.6% increase in sweep efficiency compared to CO2 WAG. Minimum miscible pressure (MMP) and interfacial tension (IFT) were reduced by 30.1 and 97.5%, respectively, significantly improving the mobility of the oil. As a result, the amount of oil remaining in the reservoir decreased by 40.7%, and oil recovery increased by 31%. An economic evaluation considering optimized injection design and reuse of recovered DME showed a 13% improvement in net present value (NPV) of CO2-DME WAG over CO2 WAG.