Reactive Transport and Convective Mixing During CO2 Migration in a Saline Aquifer

E. Abarca[1], A. Nardi[1], F. Grandia[1], J. Molinero[1]
[1]Amphos21 Consulting, Barcelona, Spain

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.