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Geologic Sequestration of Carbon



Image: Schematic diagram showing impacts of CO2 leakage into groundwater and the vadose zone.
Schematic diagram showing impacts of CO2 leakage into groundwater and the vadose zone.
Geologic Sequestration of Carbon

Geologic sequestration is the injection and subsequent long-term trapping of carbon dioxide in an underground location. This reduces the amount of carbon dioxide (a greenhouse gas) in the atmosphere. Underground Injection Control Program

Geologic sequestration (GS) is recognized as the injection and subsequent long-term trapping of gaseous, liquid, or supercritical carbon dioxide (CO2) in subsurface media, primarily saline formations, depleted or nearly depleted oil and gas reservoirs, and coal seams. Carbon capture, transport, and storage via GS from stationary sources of CO2 (such as refineries, and coal-fired electric, ethanol, cement, and fertilizer plants) could allow continued use of fossil fuels in a manner that greatly reduces CO2 emissions until alternative energy sources are deployed on a large scale in the coming decades.

Leakage through transmissive faults (and associated fractures) and well penetrations could result in:

  • Intrusion of CO2 or brine into underground sources of drinking water
  • Release of CO2 to the vadose zone and the atmosphere
  • Intrusion of CO2 into buildings

Leakage of CO2 into groundwater could result in decreased pH, increased mineral dissolution, and possible release of metal and metalloid contaminants. On the other hand, increases in CO2 concentrations could result in increased attenuation of certain metals and act to retard contaminant migration. Release of CO2 into the vadose zone could be accompanied by compositional changes in soil gas and flux to the atmosphere. Release of CO2 into buildings could result in increased CO2 and potential reduction in oxygen in indoor air.


Wilkin, R.T. and DiGiulio, D.C. (2010). “Geochemical Impacts to Groundwater From Geologic Carbon Sequestration: Controls on pH and Inorganic Carbon Concentrations From Reaction Path and Kinetic Modeling.” Environmental Science and Technology, 44: 4821–4827.

Understanding Geochemical Impacts of Carbon Dioxide Leakage From Carbon Capture and Sequestration – Science in Action Fact Sheet (PDF) (2 pp, 772 KB) (EPA/600/F-09/003) 2009

Use of Soil-Gas, Gas-Flux, and Ground Water Monitoring to Evaluate Potential Leakage to Underground Sources of Drinking Water, the Atmosphere, and Buildings During Geological Sequestration of Carbon Dioxide – Science in Action Fact Sheet (PDF) (2 pp, 768 KB) (EPA/600/S-09/030) 2009

Schnaar, G. and D.C. DiGiulio. (2009). “Computational Modeling of the Geologic Sequestration of Carbon Dioxide.” Vadose Zone J., 8: 389–403. doi:10.2136/vzj2008.0112.


DiGiulio, D.C. (2009). “Geological Sequestration of CO2: A Brief Overview and Potential for Application for Oklahoma (PDF).”(36 pp, 5.08 MB) Presentation, 18th Annual Oklahoma Clean Lakes and Watersheds Association, April 1–3.

DiGiulio, D.C. (2009). “Overview of Internal Research on Geological Sequestration of CO2 at ORD (PDF).” (26 pp, 2.74 MB) Presentation, Midwest Carbon Sequestration Conference, Angola, Indiana, July 28–29.


Development of Leak, Purge, and Gas Permeability Testing Methods to Enable Collection of Representative Soil-Gas Samples and Evaluation of Gas Leakage Into the Vadose Zone From Geological Sequestration of CO2

Development of Methods to Evaluate Gas Intrusion Into Buildings From Geological Sequestration of CO2 Using Natural and Anthropogenic Analogues

Evaluation of Geochemical Impacts to USDWs From Geologic Sequestration of CO2

Evaluation of the Use of Soil-Gas, Gas Flux, and Ground Water Monitoring to Detect Leakage of Fluids Into Underground Sources of Drinking Water (USDWs), the Vadose Zone, and the Atmosphere via Well Penetrations and Transmissive Faults From Geologic Sequestration of CO2


Richard Wilkin

Dominic DiGiulio
Acting Branch Chief

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