TECHNICAL AND ECONOMIC-FEASIBILITY OF CO2 DISPOSAL IN AQUIFERS WITHINTHE ALBERTA SEDIMENTARY BASIN, CANADA

A three year study of the technical and economic feasibility of aquife r disposal of CO2 in the low permeability sedimentary rocks of the Alb erta Basin has revealed several new generic concepts that may be appli cable to other sedimentary basins throughout the world. High permeabil ity aquifers are not necessarily required for CO2 disposal. Injectivit y of CO2 can be maximized by siting disposal wells in targeted or ''sw eet'' zones of locally high permeability surrounded by a low regional scale permeability [1-2]. The low regional permeability forms a ''hydr odynamic'' or ''time'' trap for CO2 [1], where the residence time of C O2 in the aquifer is of the order of 10(5) to 10(6) years. Another typ e of hydrodynamic trapping in sedimentary basins is produced by the '' sponge'' or ''sink'' effect of rebounding shales [3-4]. On a smaller t ime scale, over hundreds of years, ''mineral'' or ''inert'' trapping [ 5-6] by reaction of the CO2 with basic aluminosilicate minerals will o ccur in siliciclastic aquifers. Consequently, stratigraphic traps may not be necessary for safe disposal of CO2 in the subsurface. Aquifer d isposal of CO2 is expensive, on the order of $52/tonne. Although there are many possibilities to reduce CO2 emissions that are more economic ally attractive, aquifer disposal remains as one of the largest sinks available for CO2 in landlocked areas of the world; and may be utilize d if other less expensive options are exhausted.