CO2 migration in saline aquifers: regimes in migration with dissolution

We incorporate CO2 dissolution due to convective mixing into a sharp-interface mathematical model for the post-injection migration of a plume of CO2 in a saline aquifer. The model captures CO2 migration due to groundwater flow and aquifer slope, as well as residual trapping and dissolution. We also account for the tongued shape of the plume at the end of the injection period. We solve the model numerically and identify three regimes in CO2 migration with dissolution, based on how quickly the brine beneath the plume saturates with dissolved CO2. When the brine saturates slowly relative to plume migration, dissolution is controlled by the dimensionless dissolution rate. When the brine saturates "instantaneously" relative to plume migration, dissolution is instead controlled by the solubility of CO2 in brine. We show that dissolution can lead to a several-fold increase in storage efficiency. In a companion paper, we study migration and pressure limitations on storage capacity [Szulczewski et al., GHGT-10, Paper 917 (2010)]. (C) 2011 Published by Elsevier Ltd.