The long-term fate of CO2 injected into an aquifer

Assuming that an underground aquifer is capped by a capillary seal, preventing injected CO2 migrating into the atmosphere, the CO2 will eventually accumulate under this seal. The topography of the seal will determine the CO2 migration on the 1000 years time-scale. CO2 diffusing into the underlying aquifer column will set up convective currents in the aquifer, enhancing the solution rate Of CO2. Most of the CO2 will have dissolved into the aquifer after between 5000 and 50,000 years, mostly dependent on the vertical permeability of the aquifer and the contact area between CO2 and brine. On a time scale of several hundred thousand years, molecular diffusion through the capillary seal will be the dominating transport mechanism and will eventually deplete the formation of CO2 by transporting it into the atmosphere if reactions between CO2 and rock minerals are neglected. This process will take millions of years, however.