How the oil recovery in deep oil reservoirs is affected by injected gas types: A molecular dynamics simulation study

Abstract

Through molecular dynamic simulation, an investigation was conducted into the behavioral mechanism of gas injection for the development of deep oil reservoirs, with the response to environment taken as the critical influencing factor in EOR. In this study, medium-shallow reservoir was used for comparative analysis, while two types of reservoir were examined in bulk phase and on mineral surface. It was found that in deep reservoirs, the type of gas made little difference to the oil dissolution in bulk phase. In contrast, there was an evident sequence, CO2 ≈ C3H8 > CH4 ≈ N2, observed during the process of oil detachment from mineral surface. In addition, the reservoir environment mainly affects the dissolution of long-chain components, because short-chain components will quickly reach a fully dissolved state. Our study highlights the effect of gas types on oil displacement on a molecular level, which may help to promote the development of deep oil reservoirs.