INVESTIGATING THE EASTERN GULF OF MEXICO FOR POTENTIAL GEOLOGIC STORAGE OF CO2

Subsurface geologic storage of CO₂ (i.e., sequestration) can play a major role in offsetting greenhouse gas emissions in a manner that is safe, economical, and acceptable to the public. With an estimated 40% of U.S. anthropogenic CO₂emissions generated in the southeast, and a large proportion of these emissions are generated within 100 km of the coastline, it is critical to understand the sequestration potential of a variety of targets in the southeastern U.S. Onshore resources have been well-studied in the region, but offshore resources have been less well constrained and might offer some advantages to onshore subsurface sequestration. The Southeast Offshore Storage Resource Assessment (SOSRA) is designed to examine the offshore storage potential in the eastern Gulf of Mexico (EGOM) and along the southeastern seaboard.

Phase I is providing an overview of the basic geologic framework of the SOSRA region, identifying potential storage units with robust seals, and defining the key planning areas. Our focus here is on the potential targets in the EGOM. Preliminary assessments offshore of Alabama and Mississippi indicate that offshore storage capacity of Miocene strata exceeds 200 Gt. These shallow targets need to be assessed for sufficient seals to contain sequestered CO₂. Deeper strata may have other challenges. For example, strata deeper than 3,000 m are geopressured. Therefore, efforts are focusing on Cretaceous-Oligocene strata between depths of 1,000 and 3,000 m. Salt basins in the northwest part of the study area contain large salt-tectonic structures hosting a broad array of storage prospects. The West Florida Shelf spans the southeastern part of the study. The shelf can be characterized as a broad carbonate bank and structurally simple compared to the salt basins.

Phase II, now underway, will include a robust characterization of offshore CO₂ storage reservoirs and seals, as well as a probabilistic assessment of storage capacity.