Simulation the convective mixing of CO2 in geological formations with a meshless model

The CO2 sequestration is a multiphase and multi-material process in which the meshless method is advantageous to play a role in addressing the problems. In this study, the meshless approximations of the Moving Particle Semi-implicit method (MPS) are applied to model the convective mixing in the CO2 sequestration. In the numerical method, the domain is discretized into a set of material points or particles and the spatial derivatives in the meshless method are adopted to solve the governing equations. In the simulations, both the homogeneous and layered geological formations are investigated. It is found that the dissolution-diffusion-convection process in the convective mixing is reproduced by the numerical method. The calculated averaged CO2 dissolution agrees well with the results from a linear analysis in the homogeneous geological setting. The simulated time for the CO2 concentration to arrive at the bottom is in agreement with that calculated from the finite volume approach for various Rayleigh numbers. After validation of the numerical method, investigation is conducted to calculate the fingering structure, mixing length, and CO2 dissolution rate in the problem. The convective mixing in the layered formation is also simulated and it shows that the non-homogeneous formation plays a significant role in the CO2 dissolution as the fingering structure is affected. These simulations with both homogeneous and non-homogeneous cases clearly show that the numerical approximations show good performance in reproducing the phenomenon of the convective mixing and the meshless method can be potentially applied to handle multiphase and multi-material problems in the CO2 sequestration.