A Molecular Insight into the Effect of CO2 on Water-Polar Component Interface: Implication for CO2 EOR

Enhanced Oil Recovery (EOR) techniques, particularly CO2 injection, have garnered significant attention due to their potential to improve oil extraction efficiency while concurrently sequestering CO2. The impact of carbon dioxide on the properties of the hydrocarbon-water interface is currently not well established. The influence of CO2 on the interfacial characteristics of crude oil-water systems was examined using molecular dynamics (MD) simulations. Eight distinct interface models, varying in the ratio of polar to non-polar crude oil components, were constructed. The effect of CO2 was characterized by calculating IFT, molecular conformation and orientation, and oil-water-CO2 interaction energies. This study reveals three key findings: 1) As the concentration of CO2 increases, the IFT between polar and non-polar crude oils diminishes and ultimately plateaus. 2) Non-polar crude oil molecules exhibit ordered inter facial arrangements, while polar molecules are randomly distributed. Specifically, CO2 promotes perpendicular orientation of linear non-polar molecules and parallel alignment of cyclic non-polar molecules at the interface; 3) CO2 strengthens interactions between non-polar crude oil molecules, while initially weakening and then stabilizing interactions between polar molecules. These results provide crucial insights into hydrocarbon-water-CO2 IFT behavior and offer a theoretical basis for optimizing related industrial processes.