Top-down and bottom-up estimates of CO2 storage capacity in the UK sector of the southern North Sea Basin

Calculations of the CO₂storage capacity in the Leman Sandstone Formation and the Bunter Sandstone Formation in the data-rich southern North Sea basin, using structure contour, porosity, and isopach maps and a simulation of CO₂injection, suggest that their CO₂storage capacities are approximately 3 and up to 15 Gt CO₂, respectively. It is recognized that such data are not available for most sedimentary basins, and a simple top-down method of calculating CO₂storage capacity would be highly desirable from a policy maker's perspective, so that the storage capacity of a basin, region, or jurisdiction could readily be estimated. Therefore, the above estimates were used to calculate the amount of CO₂stored per unit area and the amount of CO₂stored per unit of pore volume in the Leman Sandstone and Bunter Sandstone formations. The results were compared to similar calculations, derived from published data, for the Utsira Sand, a CO₂storage reservoir in the northern North Sea. The mean CO₂stored per unit area of the formation is 140 kg m², and the range is 42260 kg m². The mean CO₂stored per unit pore volume is 6.3 kg m³, and the range is 1.810.0 kg m³. Two important factors that vary widely between these three North Sea reservoir formations are the total pore volume in traps and the achievable CO₂saturation; neither can be determined without detailed data.