Abstract:
A numerical simulation of CO
2 flooding was conducted to determine the impact of production parameters on enhanced oil recovery. Optimizing the CO
2 flooding parameters revealed that increasing the CO
2 injection rate enhances the oil production rate but also intensifies gas channelling, reduces the oil exchange rate, and poses a risk of fracturing the formation. While an increase in bottomhole pressure may temporarily limit the oil production rate, it is beneficial in the long term as it helps to elevate formation pressure, facilitating CO
2 miscibility with reservoir oil to improve stage recovery and oil exchange rate. Bottomhole pressure should be increased as much as possible, ensuring an injection-production balance. An increase in water cut in the block diminishes CO
2 flooding effectiveness, leading to lower recovery and oil exchange rate. During CO
2 flooding development, oil exchange rate will decline with rising production gas-oil ratio. Therefore, injection wells should be shut in timely to ensure reasonable CO
2 injection amounts. Based on these findings, optimal parameters were determined: a CO
2 injection rate of 15, 000 m
3/d, a production bottomhole pressure of 25 MPa, CO
2 injection timing at a block water cut of 60%, and shut-in timing when the production gas-oil ratio reaches 1 000 m
3/m
3, with a reasonable CO
2 injection amount of 92 000 tons. Simulation results using these optimized parameters indicated that after 9 years of CO
2 injection, crude oil production from the block increased by 213 000 tons, with a corresponding oil recovery improvement of 27.4%. The cumulative oil exchange rate reached 0.58, while the cumulative storage rate reached 0.67.