Numerical Simulation of CO₂ Diffusion in a Multiliquid-Phase System Using Moving Mesh Technology

Abstract

CO2 diffusion plays an important role in many CO2 injection techniques. But CO2 diffusion in multiliquid-phase systems has not been thoroughly investigated. Here multiliquid-phase system refers to the liquid system coexisting water, light oil, and heavy oil phases. This study investigates the CO2 concentration and the induced oil expansions when CO2 diffuses in a multiliquid-phase system. First, the mathematical model is developed based on the location of the CO2 diffusion front in the multiliquid-phase system. Second, the corresponding numerical model is established for different diffusion stages. To accurately describe the swelling of two oils, we employ the moving mesh technology to monitor the movement of two interfaces. Finally, CO2 concentration profiles, the induced oil swelling, and the movement of the CO2 front are studied by coding the developed numerical model. The results demonstrate that the CO2 concentration distribution and the induced oil swelling exhibit different performances in various phases at different diffusion stages. So it is necessary to divide the diffusion stage when studying the CO2 diffusion in a multiliquid-system. CO2 diffusion results in 19.52% and 17.21% expansion for light and heavy oil, respectively.