U.S. GEOLOGICAL SURVEY GOALS FOR CHARACTERIZATION AND ASSESSMENT OF NATURAL CARBON DIOXIDE AND HELIUM ACCUMULATIONS IN THE UNITED STATES

Naturally occurring helium (He) is used in many industrial and research applications and natural carbon dioxide (CO₂) is primarily used in enhanced oil recovery operations. Although not part of the petroleum system, He and CO₂ often occur in natural gas reservoirs. The Energy Independence and Security Act of 2007 authorized the U.S. Geological Survey (USGS) to conduct a national assessment of geologic storage resources for anthropogenic CO₂ (http://pubs.usgs.gov/circ/1386/), and to evaluate the geologic risks associated with long-term storage of CO₂ in subsurface reservoirs. To assess these risks, the USGS Carbon Sequestration Geologic Research and Assessments (CS-GRA) Project is conducting detailed studies of natural CO₂ reservoirs (those containing >10% CO₂) to determine the long-term geologic and geochemical effects of natural CO₂ storage. The information obtained from these studies can be used to help predict the geologic and environmental effects of anthropogenic CO₂ storage in geologic reservoirs. These studies include: 1) characterization of natural gas (including hydrocarbons, CO₂, and noble gases) and associated reservoir rocks by geochemical and isotopic analyses to help determine the origin (mantle, thermal carbonate alteration, or other), migration pathways, and ultimate fate of the natural CO₂; 2) characterization of associated formation water; and 3) geologic characterization of the CO₂ reservoir rocks to determine the long-term effects of natural CO₂ storage and the occurrence of CO₂ leaks from the reservoir.

The Helium Stewardship Act of 2013 directed the USGS to cooperate with the Bureau of Land Management (BLM) and the State geological surveys, to assess the availability of recoverable natural He and associated CO₂ found in natural gas reservoirs in the United States. As an initial effort, the CS-GRA Project is building a national geochemical database that can be used to evaluate the occurrence and distribution of He and CO₂ resources occurring in natural gas reservoirs in the country. Scientists from the project will use this data to build the geologic models needed to evaluate the availability and resource distribution of natural CO₂ and He. In cooperation with BLM, the CS-GRA Project plans to conduct a national assessment of undiscovered naturally occurring CO₂ and He resources.