Molecular dynamics simulation of CO2-N2 dissolution and stripping of oil films on pore walls based on intermolecular interaction energy

The interaction between crude oil and pore surfaces is notable in the process of CO2 and N2 flooding, and some crude oil can hardly be displaced and remains on pore walls in the form of oil films. The reasons for residual oil retention and stripping from pore surfaces were studied. The results indicated that in hydrophilic systems, the gas phase exhibited the ability to dissolve oil films when the CO2 mole ratio in the gas phase was not lower than 25%, and oil films can be stripped from pore surfaces only when the CO2 mole ratio was not lower than 75%. In hydrophobic systems, when the CO2 mole ratio in the gas phase was higher than 50%, the gas phase exhibited the ability to dissolve oil films. Regardless of the proportion of CO2 in the mixed gas, the gas phase did not provide the ability to strip oil films.