Technical and economic feasibility of CO2 disposal in aquifers within the Alberta Sedimentary Basin, Canada

A three year study of the technical and economic feasibility of aquifer disposal of CO2 in the low permeability sedimentary rocks of the Alberta Basin has revealed several new generic concepts that may be applicable to other sedimentary basins throughout the world. High permeability aquifers are not necessarily required for CO2 disposal. Injectivity of CO2 can be maximized by siting disposal wells in targeted or ''sweet'' zones of locally high permeability surrounded by a low regional scale permeability [1-2]. The low regional permeability forms a ''hydrodynamic'' or ''time'' trap for CO2 [1], where the residence time of CO2 in the aquifer is of the order of 10(5) to 10(6) years. Another type of hydrodynamic trapping in sedimentary basins is produced by the ''sponge'' or ''sink'' effect of rebounding shales [3-4]. On a smaller time scale, over hundreds of years, ''mineral'' or ''inert'' trapping [5-6] by reaction of the CO2 with basic aluminosilicate minerals will occur in siliciclastic aquifers. Consequently, stratigraphic traps may not be necessary for safe disposal of CO2 in the subsurface. Aquifer disposal of CO2 is expensive, on the order of $52/tonne. Although there are many possibilities to reduce CO2 emissions that are more economically attractive, aquifer disposal remains as one of the largest sinks available for CO2 in landlocked areas of the world; and may be utilized if other less expensive options are exhausted.