Molecular insight into oil displacement by CO2 flooding on rough silica surface

Rough characteristics of solid surfaces play an important role in fluid-solid interactions. In the present work, molecular dynamics (MD) simulation was used to study the oil displacement by CO2 flooding on the rectangular rough silica surface. Particular attention was given to the influence of rock roughness on oil recovery. The results showed that CO2 molecules could closely adsorb on the silica surface and drive the oil into the flooding. In the rough silica slit, the wider and deeper grooves would trap more oil molecules, and they needed a longer time to escape from the grooves. It was also pointed that the oil recovery-time relationship could be quantified using the compressed exponential function. The displacement front transformed from a concave-type meniscus to a convex-type meniscus when the groove became deeper and narrower. The study could help understand the fluid-solid interactions at the molecular level and be beneficial to more sustainable exploitation of oil.