Carbon dioxide storage capacity in uneconomic coal beds in Alberta, Canada: Methodology, potential and site identification

Methodology is presented for a first-order regional-scale estimation of CO2 storage capacity in coals under sub-critical conditions, which is subsequently applied to Cretaceous-Tertiary coal beds in Alberta, Canada. Regions suitable for CO2 storage have been defined on the basis of groundwater depth and CO2 phase at in situ conditions. The theoretical CO2 storage capacity was estimated on the basis of CO2 adsorption isotherms measured on coal samples, and it varies between ∼20 kt CO2/km2 and 1260 kt CO2/km2, for a total of approximately 20 Gt CO2. This represents the theoretical storage capacity limit that would be attained if there would be no other gases present in the coals or they would be 100% replaced by CO2, and if all the coals will be accessed by CO2. A recovery factor of less than 100% and a completion factor less than 50% reduce the theoretical storage capacity to an effective storage capacity of only 6.4 Gt CO2. Not all the effective CO2 storage capacity will be utilized because it is uneconomic to build the necessary infrastructure for areas with low storage capacity per unit surface. Assuming that the economic threshold to develop the necessary infrastructure is 200 kt CO2/km2, then the CO2 storage capacity in coal beds in Alberta is greatly reduced further to a practical capacity of only ∼800 Mt CO2.