Simulation and Modeling of Convective Mixing of Carbon Dioxide in Geological Formations

We perform large‐scale numerical simulations of convection in 3D porous media at Rayleigh‐Darcy numbers up to Ra = 8 × 104. To investigate the convective mixing of carbon dioxide (CO2) ingeological formations, we consider a semi‐infinite domain, where the CO2 concentration is constant at the topand no flux is prescribed at bottom. Convection begins with a diffusion‐dominated phase, transitions toconvection‐driven solute finger growth, and ends with a shutdown stage as fingers reach the bottom boundaryand the concentration in the system increases. For Ra ≥ 5 × 103, we observe a constant‐flux regime withdissolution flux stabilizing at 0.019, approximately 13% higher than in 2D estimates. Finally, we provide asimple and yet accurate physical model describing the mass of solute entering the system throughout the wholemixing process. These findings extend solutal convection insights to 3D and high‐Ra, improving the reliabilityof tools predicting the long‐term CO2 dynamics in the subsurface