Study on the Asphaltene Precipitation in CO2 Flooding: A Perspective from Molecular Dynamics Simulation

Asphaltene precipitation is a common phenomenon in the exploitation of crude oil and closely correlates with oil recovery, especially in CO(2 )flooding. In this work, employing molecular dynamics simulations, the asphaltene precipitation process in CO2 was investigated. The simulation results reveal that the CO2 could stepwise extract nonpolar and light polar components from asphaltene micelle, and a two-step asphaltene precipitation process was illustrated. In our eight molecule asphaltene system, first four asphaltene dimers formed. Two dimers get together into one aggregation in bulk; the other two dimers get together and adsorbed onto the silica surface. After that, the surface aggregation further induces the adsorption of bulk aggregation onto it to complete asphaltene precipitation. In addition, we also studied the pressure effect on asphaltene precipitation. Our work provided a molecular-level understanding of asphaltene precipitation phenomenon in CO(2 )flooding, and the results have significant promise for oil exploitation.