Molecular Dynamics Insight into the CO₂ Flooding Mechanism in Wedge-Shaped Pores

L Wang and W Lyu and ZM Ji and S Liu and HX Fang and XK Yue and SX Wei and SY Liu and ZJ Wang and XQ Lu, MOLECULES, 28, 188 (2023).

DOI: 10.3390/molecules28010188

Because of the growing demand for energy, oil extraction under complicated geological conditions is increasing. Herein, oil displacement by CO2 in wedge-shaped pores was investigated by molecular dynamics simulation. The results showed that, for both single and double wedge-shaped models, pore II (pore size from 3 to 8 nm) exhibited a better CO2 flooding ability than pore I (pore size from 8 to 3 nm). Compared with slit-shaped pores (3 and 8 nm), the overall oil displacement efficiency followed the sequence of 8 nm > double pore II > single pore II > 3 nm > double pore I > single pore I, which confirmed that the exits of the wedge-shaped pores had determinant effects on CO2 enhanced oil recovery over their entrances. "Oil/CO2 inter-pore migration" and "siphoning" phenomena occurred in wedge-shaped double pores by comparing the volumes of oil/CO2 and the center of mass. The results of the interaction and radial distribution function analyses indicate that the wide inlet and outlet had a larger CO2-oil contact surface, better phase miscibility, higher interaction, and faster displacement. These findings clarify the CO2 flooding mechanisms in wedge-shaped pores and provide a scientific basis for the practical applications of CO2 flooding.

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