A Sub-Grid Model for Convective Mixing Applied to the 11th SPE Comparative Solution Project

Summary Solubility trapping, involving the dissolution of supercritical carbon dioxide (CO2) into resident brine, is crucial for geological carbon storage. Density-driven convective mixing enhances solubility trapping but is challenging to model in standard reservoir simulations due to its centimeter-scale nature. We present the appliation of a sub-grid model for convective mixing in geological carbon storage, designed for coarse-grid simulation. This model includes a dynamic partitioning algorithm to relax phase equilibrium assumptions in large cells and an effective transport component to enhance subscale unstable flow and transport modeling. The approach is implemented in the Open Porous Media (OPM) Flow simulator and has previously been validated on 2D field-scale geometries in a simple setup. Our study applies this model to the 11th SPE Comparative Solution Project (SPE11) to address simulation challenges in CO2 storage operations in geologically complex settings. The sub-grid model is used in SPE11 Cases B and C, 2D and 3D geometries at realistic operational conditions. The study shows that the sub-grid model yields dissolution rates comparable to those from fine-scale simulations on Case B. For Case C, fine-scale reference simulations are unavailable, but the results show trends similar to those of Case B. The results showcase its utility for improving CO2 dissolution estimates and for exploring parameter sensitivities in realistic storage projects.