Modeling CO2 plume migration using an invasion-percolation approach that includes dissolution

Geological carbon dioxide (CO2) sequestration has been proposed as a viable technique to decrease effective emissions of CO2 into the atmosphere. However, the security of this sequestration is tied to our understanding of the long-term migration of CO2 in subsurface. The dissolution of CO2 in the reservoir brine is one of the main long-term trapping mechanisms. However, the assumptions used in large-scale reservoir simulations usually lead to an overestimation of the dissolution volume. We propose a modified approach based on the macroscopic invasion-percolation (MIP) theory that allows the dissolution of CO2 into brine. We used a high-resolution geological model to compare the Darcy-, modified MIP-, and classic MIP-based simulation results. We observed a significant shrinkage in the nonaqueous plume volume when dissolution is considered during the MIP simulation. In the case of Darcy-based simulation, the plume was completely trapped inside the reservoir with limited migration even after a thousand-year simulation. On the other hand, the majority of the plume migrated out of the simulated reservoir in the case of MIP. Our approach provides more realistic estimation of the dissolution volume and nonaqueous plume extent while leveraging the computational efficiency enjoyed by MIP. (c) 2020 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons, Ltd.