Molecular dynamics investigation on the solubility parameters of supercritical CO₂ and petroleum hydrocarbon

In the process of oil exploitation, some crude oil will be difficult to extract clearly, resulting in a reduced recovery rate and waste of resources. Supercritical CO₂is a green solvent with excellent properties. The use of supercritical CO₂to drive oil flow can enhance oil extraction and improve oil recovery. It is important to investigate the microscopic mechanism of petroleum hydrocarbon extraction by supercritical CO₂at the molecular level. The compatibility between supercritical CO₂and various petroleum components was studied using molecular dynamics simulations. The dissolution process of petroleum molecules in supercritical CO₂was analyzed, and the strengthening effect of cosolvents on the dissolution process was discussed. The results show that the solubility parameter value of supercritical CO₂is less sensitive to pressure changes under low temperature conditions than to pressure changes under high temperature conditions. For different kinds of petroleum hydrocarbons, the solubility parameters of alkane and aromatic hydrocarbons gradually increased with the increase in carbon number. The solubility parameters of naphthene didn’t change significantly with the increase in carbon number. Furthermore, the addition of cosolvent in supercritical CO₂could effectively improve the solubility of petroleum hydrocarbon molecules, among which methanol has the best solubilization effect. Adding 10% methanol can reduce the solubility parameter difference between supercritical CO₂and benzopyrene by 25.49%.