The Three-Dimensional Heterogeneous Simulation Study of CO2 Flooding in Low-Permeability Reservoirs

CO2 flooding can significantly enhance oil recovery. However, the research on the distribution of remaining oil after CO2-oil and the method of further enhancing oil recovery still needs to be strengthened. Traditional studies on the mechanisms of CO2 flooding to enhance oil recovery mainly focus on core displacement experiments. In order to better simulate the actual field conditions, we conducted a three-dimensional heterogeneous physical simulation experiment. Compared to conventional core displacement experiments, three-dimensional heterogeneous physical model displacement experiments align more closely with actual conditions at the oilfield site. This study establishes a large-scale indoor three-dimensional high-temperature high-pressure displacement physical model and employs three different oil displacement methods: CO2–Water alternating flooding, CO2–Water alternating combined with foam flooding, and CO2–Water alternating combined with imbibition agent flooding. The study investigates the distribution of residual oil and recovery in heterogeneous reservoirs under different injection and production methods. We proposed three experimental schemes to see which one would have better effects in the oilfield. Experimental results show that CO2–Water alternating flooding combined with different chemical flooding agents improves oil recovery. The CO2–Water alternating combined with an imbibition enhancer flooding method achieves the best results, with recovery increased by 16.3% and 1.7% compared to CO2–Water alternating flooding and CO2–Water alternating combined with foam flooding, respectively. The imbibition agent significantly improves wettability and spontaneous imbibition by reducing interfacial tension and resolving the issue of CO2 failing to enter small pores under low differential pressure conditions, thereby maximizing recovery and displacement efficiency.