Specific Storage Volumes: A Useful Tool for CO2 Storage Capacity Assessment

Subsurface geologic strata have the potential to store billions of tons of anthropogenic CO₂; therefore, geologic carbon sequestration can be an effective mitigation tool used to slow the rate at which levels of atmospheric CO₂ are increasing. Oil and gas reservoirs, coal beds, and saline reservoirs can be used for CO₂ storage; however, it is difficult to assess and compare the relative storage capacities of these different settings. Typically, CO₂ emissions are reported in units of mass, which are not directly applicable to comparing the CO₂ storage capacities of the various storage targets. However, if the emission values are recalculated to volumes per unit mass (specific volume) then the volumes of geologic reservoirs necessary to store CO₂ emissions from large point sources can be estimated. The factors necessary to convert the mass of CO₂ emissions to geologic storage volume (referred to here as Specific Storage Volume or ‘SSV’) can be reported in units of cubic meters, cubic feet, and petroleum barrels. The SSVs can be used to estimate the reservoir volume needed to store CO₂ produced over the lifetime of an individual point source, and to identify CO₂ storage targets of sufficient size to meet the demand from that given point source. These storage volumes also can then be projected onto the land surface to outline a representative “footprint,” which marks the areal extent of storage. This footprint can be compared with the terrestrial carbon sequestration capacity of the same land area. The overall utility of this application is that the total storage capacity of any given parcel of land (from surface to basement) can be determined, and may assist in making land management decisions.