SPECIFIC STORAGE VOLUMES: A RESOURCE ASSESSMENT VIEW OF CO2 STORAGE CAPACITY

Geologic systems have the potential to store billions of tons of anthropogenic CO₂, thus alleviating the rising levels of atmospheric CO₂. However, there is a need to assess the total amount of storage space available for CO₂ in these systems. Among the geologic systems that will be used for storing CO₂ are oil and gas reservoirs, coal beds, and saline reservoirs; however, it is difficult to assess the relative storage capacities of the various systems. A new approach to the issue of storage capacity is to view capacity as a finite volumetric resource that will be consumed. This approach allows for the direct comparison of the relative capacities of the various geologic systems. Anthropogenic CO₂ from point sources is reported as tons of CO₂ emitted, that mass needs to be converted to a storage volume for the various geologic targets.

If CO₂ emissions are recalculated as units of specific volume, i.e. volume per unit mass, then the volumes of geologic reservoirs necessary to store CO₂ emissions from large point sources can be estimated. Specific Storage Volume (SSV) is defined as the factors necessary to convert the mass of CO₂ emissions to geologic storage volume. The SSV’s can be reported in units of cubic meters, cubic feet, and petroleum barrels, and then can be compared to reference volumes common to hydrogeology and the petroleum industry. The SSV’s also can be used to determine the volume of the geologic system that will be needed to store the CO₂ produced over the lifetime of an individual point source, to identify storage targets of sufficient size to meet the demand from that given point source.

The further benefit of this method is that once the storage volume is calculated, the volume can be projected onto the land surface. This representative “footprint” marks the areal extent of the storage resource that has been consumed during CO₂ storage. This footprint can be compared with the terrestrial 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.