Intermittent Water Injection on Top of Continuous CO2 Injection to Co-Optimize Oil Recovery and CO2-Storage

Abstract

The objective of this project is to maximize oil recovery and the CO2 stored during CO2-EOR. To reach that goal there are two important things to be achieved: gas production rate reduction and the oil production rate improvement. To attain the co-optimization, the following CO2 injection approaches were compared: CO2 continuous injection, WAG, Continuous water injection over continuous CO2 injection, and intermittent water injection over continuous CO2 injection. The comparison was done by using a commercial simulation program CMG GEM 2015. It was learned from this work that the water injection over the CO2 injector would offer the best way to increase the CO2 stored. It was found that increasing the water injection rate and injection length would increase the CO2 stored in the reservoir due to the reduction in gas-oil mobility ratio. However, the oil recovered would be reduced due to the increase of water-oil mobility ratio. This project presented the importance of carefully adjusting the water injection configuration during the lifetime of CO2-EOR on achieving the co-optimization goal. Compared to the continuous CO2 injection scenario, the highest oil recovery case resulted in the following: 4.46% OOIP oil recovery increase, 8% more CO2 stored, and reduction in CO2 utilization factor from 5.22 tCO2/Sm3 oil to 4.15 tCO2/Sm3 oil. The reduction in the CO2 utilization factor shows that this approach would be economically and practically attractive.