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Offshore Characterization Field Projects

Regional Initiative Overview

Figure 1: Offshore saline storage potential. Click to enlarge.

The United States (U.S.) Department of Energy (DOE) has completed studies to estimate the storage resource on the continental shelf off the Atlantic and Gulf coasts of the U.S. The projects used a variety of methodologies and covered different geologic settings offshore of the Gulf of Mexico (GOM) and the Atlantic coasts.

Currently DOE is funding two offshore partnerships to assemble the knowledge base required for secure, long-term, large-scale carbon dioxide (CO2) storage, with or without enhanced hydrocarbon recovery, and assess technology-development needs (infrastructure, operational, monitoring), which differ from those onshore.

The advantages of offshore CO2 storage for the U.S. include:

  • CO2 storage is provided in areas of many large, stationary CO2 sources along coastlines and areas that may have potentially limited options for onshore CO2 storage.
  • Issues with heavily populated, onshore areas are avoided.
  • Typically, there is one owner for leasing and pipeline siting.
  • Mineral rights are owned by the state or federal government.
  • Formation fluid in offshore sediments is typically similar to sea water in terms of chemistry and salinity (30,000 to 40,000 parts per million [ppm] total dissolved solids [TDS]).
  • Potential reduced risks to underground sources of drinking water (USDWs).

Considerations in determining the suitability of a formation for storage include:

  • In onshore saline formations, a minimum depth of about 914 meters (3,000 feet) is required for adequate fluid pressures and temperatures to store CO2 in the supercritical state, minimizing the volume of required storage space. In offshore saline formations, the minimum depth below the seabed is less because the column of water above increases the pressure on the formation.
  • U.S. Environmental Protection Agency (EPA) water-quality guidelines require a minimum pore water TDS of 10,000 ppm for assessed saline storage formations, which is unlikely to be an issue offshore.
  • The requirement of a suitable seal system, such as a caprock, to limit vertical flow of the CO2 to the surface.

GOMCarb map
Figure 2: The current offshore partnership study areas. Click to enlarge
The Partnership for Offshore Carbon Storage Resources and Technology Development in the Gulf of Mexico (GoMCARB): The GoMCarb partnership compiles data and expertise in the region, integrating academic research institutions, government entities, and industry affiliates to address knowledge gaps, regulatory issues, infrastructure requirements, and geologic and engineering technical challenges of storing CO2.

Southeast Regional Carbon Storage Partnership: Offshore Gulf of Mexico (SECARB GOM): SECARB GOM is leading a coalition of southern universities and technical experts to expand the existing GOM government-industry partnership and focus on assembling the knowledge base required for secure, long-term, large-scale CO2 subsea storage.

Offshore GOM Map
Figure 3 shows the study areas of four DOE-funded projects focused on assessing the CO2 storage resource in the GOM. Click to enlarge.
Sediments beneath the GOM represent a vast storage resource in oil and gas reservoirs and saline formations, and resource estimates benefit from extensive oil and gas exploration and development data. Using production data, it is estimated that there are 20 billion metric tons of storage in just the oil and gas reservoirs. Including saline formations, analysis of seismic data and well data indicates that hundreds of billions of metric tons, or more, storage resource is available in the Gulf.

Detailed discussion of the results of these studies are provided by Savage and Ozgen and Agartan et al., Bruno et al., Nemeth et al. and https://www.beg.utexas.edu/gccc/research/osra.

 

Atlantic map
Figure 4: Study areas of DOE funded projects to assess the CO2 storage resource in the offshore Atlantic. Click to enlarge.
Storage resource estimates are less well-defined off the Atlantic coast due to lack of data. Nonetheless, improved stratigraphic models, guided by biostratigraphy and combined with available seism ic data, indicate hundreds of billions of metric tons, or more, of storage resource is also available throughout a large study area from New York to northern Florida.

Detailed discussion of the results of these studies are provided by Gupta, Nemeth et al.

 

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