AQUIFER DISPOSAL OF CO2 - HYDRODYNAMIC AND MINERAL TRAPPING

A general approach to evaluating sedimentary basins for CO2 disposal is presented in this paper. The approach is exemplified for the case of the Alberta Basin in western Canada where a wealth of geological and hydrogeological data from more than 150,000 wells drilled by the oil industry allows for a proper estimate of the basin potential for long-term storage of CO2 captured from fossil-fuelled power plants. Geochemical and hydrogeological analyses of CO2 interaction with the aquifer water and rocks, and of CO2 transport in miscible and immiscible phase by the natural flow of aquifer water indicate that, besides stratigraphic trapping, two additional mechanisms are available for the capture and long-term retention of CO2 in the subsurface. One mechanism is mineral trapping through precipitation of carbonate minerals when CO2 is injected into basic siliciclastic aquifers. The other mechanism is hydrodynamic trapping when the residence or travel time of CO2 in low permeability regional aquifers is of the order of thousands to a million years.