Efficiency of Dissolution Trapping in Geological Carbon Storage

During geological storage of carbon dioxide (CO2), several mechanisms contribute to safe storage by immobilizing the CO2 in the injection formation. It has been shown that dissolution into resident brine can be one of the major contributors. The injected supercritical CO2 is buoyant, but dissolved CO2 increases brine density and therefore reduces the tendency for upward CO2 migration. The density increase with dissolved CO2 leads to convective mixing of the brine, thereby enabling more CO2 to dissolve. It is important to quantify the efficiency of CO2 dissolution, and therefore the efficiency of convective mixing. In previous work, we have shown that convective mixing can be considerably enhanced when taking into acccount the interaction between the two-phase region (supercritical CO2 and brine), and the single-phase brine region. Bounds on this impact were obtained for onset times, wavelengths of unstable fingers, and dissolution rates. The maximum increase in the dissolution rate was found to be large, when interaction with the plume was considered. In this paper, we use stability analysis to further study the dissolution in more detail. We make technical contributions to the field of stability analysis and in obtaining more reliable estimates of the efficiency of dissolution trapping.