Long Time Evolution of Sequestered CO2 in Porous Media

CO₂ sequestration is important for mitigating climate change and reducing atmospheric CO₂ concentration. However, a complete physical picture able to predict both the pattern formation and the structure developing within the porous medium is lacking. We propose a theoretical model that couples transport, reaction, and the intricate geometry of the rock, in order to study the long time evolution of carbon in the brine-rock environment. As CO₂ is injected into a brine-rock environment, it becomes initially trapped, and isolated bubbles are formed. Within the high CO₂ phase, minerals dissolve and migrate from high concentration to low concentration regions, along with other carbonate species. The change in the concentrations at the interface moves the system out of equilibrium, drives up the saturation level, and leads to mineral precipitation. We argue that mineral precipitation in a small boundary layer may lead to lower diffusivity, slower kinetics, and eventually to a mechanical trapping of the CO₂ bubbles. We investigate the reactive transport model and study the conditions that cause the mechanical separation of these two reactive fluids in porous media.