Comparison of Geologic Parameters Pertinent to CO2 Sequestration within Mature Hydrocarbon Provinces of the United States

Sequestration of CO₂ in geologic media may become a key mitigation strategy in the face of climate change. Additionally, CO₂ sequestration may represent a key energy technology because injection into mature oil and gas fields can enhance the recovery of increasingly scarce hydrocarbons. Presently, tens of CO₂ sequestration pilot sites exist worldwide, but the number of sites would need to increase by orders of magnitude in order to offset a significant portion of the global carbon budget. Project planning can be aided by comparing geologic properties of stratigraphic packages in prospective sedimentary basins. To this end, the U.S. Geological Survey is evaluating stratigraphic packages in ~20 of the largest oil and gas producing basins in the United States. For the sake of comparison, we parse the basins into 6 chronostratigraphic packages, which approximately correspond to major geologic divisions across most of North America. These packages are the Cambrian-Devonian, Carboniferous-Triassic, Jurassic, Cretaceous, Paleogene, and the Neogene. We characterize each package on the basis of five criteria which are critical in project planning. The first criterion is the aggregated seal thickness, which provides an indication of the likelihood for long-term CO₂ containment. Similarly, we aggregate the thickness of reservoir intervals, which provides an indication of potential storage capacity. The third criterion is the number of reservoir/seal pairs within a package, which bears on both storage and containment capacity. The fourth criterion is the mean reservoir porosity, which influences both the capacity of a given reservoir and the reservoir permeability. Finally, we summarize the percentage of the reservoir area that contains formation waters with a concentration of total dissolved solids below 10,000 ppm; such waters are considered potable by the U.S.

Environmental Protection Agency and are off limits for CO₂ storage. The information is compiled into a series of maps that can be compared to existing compilations of CO₂ point sources or oil and gas field locations. Moreover, the compilation highlights important regional geologic patterns relevant to CO₂ sequestration. For example, whereas Cretaceous strata around the interior Rockies are characterized by good reservoirs and seals, they also contain large quantities of potable water. The Tertiary strata of the Gulf Coast appear to contain good reservoirs and seals and predominantly saline formation waters.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California