Geological Storage Capacity for CO2 in the United States

July 16, 2012, 9:16 pm
Source: Crs

Carbon capture and sequestration (or storage)—known as CCS—is capturing carbon at its source and storing it before its release to the atmosphere. CCS would reduce the amount of carbon dioxide (CO2) emitted to the atmosphere despite the continued use of fossil fuels. An integrated CCS system would include three main steps: (1) capturing and separating CO2; (2) compressing and transporting the captured CO2 to the sequestration site; and (3) sequestering CO2 in geological reservoirs or in the oceans.

Three main types of geological formations are being considered for carbon sequestration:

(1) depleted oil and gas reservoirs,

(2) deep saline reservoirs, and

(3) unmineable coal seams.

In each case, CO2 would be injected, in a dense form, below ground into a porous rock formation that holds or previously held fluids. See Carbon capture and storage for details.

According to the U.S. Department of Energy 2008 Carbon Sequestration Atlas, at least one of each of the three main types of types of potential geological reservoirs for CO2 occurs across most of the United States in relative proximity to many large point sources of CO2, such as fossil fuel power plants or cement plants. The 2008 Carbon Sequestration Atlas replaces the 2007 version, and contains a substantial expansion of the estimated storage capacity for oil and gas reservoirs and for deep saline formations compared to 2007 estimates. Table 1 shows the 2008 estimates and compares them to estimates from the 2007
version.

Table 2. Geological Sequestration Potential for the United States and Parts of Canada
(comparing 2008 and 2007 estimates, GtCO2)

 

Reservoir type

Lower estimate
(2008)

Lower estimate
(2007)

 % change

Upper estimate
(2008)

Upper estimate
(2007)

% change

 Oil and gas fields

 138

 82.4

 +67%

 —

 —

 —

 Deep saline formations

 3,297

  919.0

 +259%

 12,618

 3,378.0

 +274%

 Unmineable coal seams

 157

 156.1

+0.6%

 178

 183.5

  -3.0%

 Source: 2008 and 2007 Carbon Sequestration Atlases

The Carbon Sequestration Atlas was compiled from estimates of geological storage capacity made by seven separate regional partnerships, government-industry collaborations fostered by DOE, that each produced estimates for different regions of the United States and parts of Canada. According to DOE, geographical differences in fossil fuel use and sequestration potential across the country led to a regional approach to assessing CO2 sequestration potential. The Carbon Sequestration Atlas reflects some of the regional differences; for example, not all of the regional partnerships identified unmineable coal seams as potential CO2 reservoirs. Other partnerships identified geological formations unique to their regions—such as organic-rich shales in the Illinois Basin, or flood basalts in the Columbia River Plateau—as other types of possible reservoirs for CO2 storage.

Table 1 indicates a lower and upper range for sequestration potential in deep saline formations and for unmineable coal seams, but only a single estimate for oil and gas fields. The 2007 Carbon Sequestration Atlas explained that a range of sequestration capacity for oil and gas reservoirs is not provided—in contrast to deep saline formations and coal seams—because of the relatively good understanding of oil and gas field volumetrics. Although it is widely accepted that oil and gas reservoirs are better understood, primarily because of the long history of oil and gas exploration and development, it seems unlikely that the capacity for CO2 storage in oil and gas formations is known to the level of precision stated in the 2008 Carbon Sequestration Atlas. It is likely that the estimate of 138 GtCO2 shown in Table 1 may change, for example, pending the results of large-scale CO2 injection tests in oil and gas fields.

Each partnership produced its own estimates of reservoir capacity, and some observers have raised the issue of consistency among estimates across the regions. The Energy Independence and Security Act of 2007, enacted as P.L. 110-140 on December 19, 2007, directed the U.S. Department of the Interior (DOI) to develop a single methodology for an assessment of the national potential for geologic storage of carbon dioxide. Under P.L. 110-140, the U.S. Geological Survey (USGS) within DOI is directed to complete an assessment of the national capacity for CO2 storage in accordance with the methodology. The law gives the USGS two years following publication of the methodology to complete the national assessment. According to DOE, the USGS effort will allow refinement of the estimates provided in the 2008 Carbon Sequestration Atlas, and will incorporate uncertainty in the capacity estimates. The DOE Sequestration Atlas should probably be considered an evolving assessment of U.S. reservoir capacity for CO2 storage.

Further Reading

  1. U.S. Dept. of Energy, National Energy Technology Laboratory, 2008 Carbon Sequestration Atlas of the United States and Canada, 2nd ed. (November 2008), 140 pages. 

Note: The first version of this article was drawn from Carbon Capture and Sequestration by Peter Folger, Congressional Research Service, February 23, 2009. 


 

Disclaimer: This article is taken wholly from, or contains information that was originally published by, the Congressional Research Service. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the Congressional Research Service should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.

Glossary

Citation

(2012). Geological Storage Capacity for CO2 in the United States. Retrieved from http://www.eoearth.org/view/article/51cbedd87896bb431f694588

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