NATURAL CO_2 OCCURRENCES COMPARED TO ANTHROPOGENIC CO_2 INJECTION SITES WITHIN THE WILLISTON BASIN, CENTRAL NORTH AMERICA

摘要

On the western flank of the Williston Basin, southwestern Saskatchewan, Canada, CO_2 occurs in natural accumulations within Devonian carbonates and Cambrian siliciclastics. Inert gases from some carbonate reservoirs contain greater than 80 per cent CO_2 and have sustained flow rates up to 425, 000 m~3 /day. Early estimates of this resource suggested nearly two million tonnes of CO_2 or about one billion m~3 of recoverable gas are present in these rocks. These natural CO_2 occurrences are found about 400 km west of the site of the IEA Weyburn CO_2 Storage and Monitoring Project (Figure 1), which is directed toward assessing the potential for safe geological storage of anthropogenic CO_2 in Mississippian carbonates. The Devonian strata containing natural CO_2 accumulations in southwestern Saskatchewan are geologically very similar to the Mississippian beds being injected with CO_2 at the Weyburn Field.