Reactive Transport and Convective Mixing During CO2 Migration in a Saline Aquifer
The capture and storage of CO2 in deep geological formations is one of the proposed solutions to reduce CO2 emissions to the atmosphere. CO2 is injected as a supercritical fluid deep below a confining geological formation that prevents its return to the atmosphere. A configuration of denser CO2-enriched brine overlying lighter water leads to convective flow and the formation of gravity fingers of dense fluid sinking into the resident brine. In this work, we use COMSOL Multiphysics® combined with PHREEQC to analyze the interaction between flow and reactive transport processes associated with the dissolution of CO2 in brine in a carbonated aquifer. Fingering of acidic CO2-rich brine can lead to non-uniform calcite dissolution and gypsum precipitation patterns and therefore to heterogeneity in the porosity of the system.