Molecular insight into the oil displacement mechanism of gas flooding in deep oil reservoir

Gas flooding has become one important development method for deep reservoir. In this work, employing molecular dynamic simulation method, the displacement behavior of nanoslit oil by injected gases (CO2, CH4, N2, C3H8) was investigated. Simulation results indicate that the injected gases exhibit great advantage in deep reservoir than that in medium-shallow reservoir, the displacement capability follows order of CO2 > C3H8 > CH4 > N2. The dissolubility of gas, adsorption strength of oil, and detachment capability of injected gas play crucial roles in displacement performance. Our work highlights the effect of gas types on displacement performance, which is significant for the development of deep oil reservoirs.