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September 27, 2023

Can the very reservoirs where petroleum was produced be used to store carbon? The USGS went to find out!

Oil and gas produced from reservoirs are traditionally thought of as sources of carbon dioxide and other greenhouse gases. The petroleum that is pumped up from the depths is one of the largest contributors to climate change, after all. Therefore, in recent years, scientists in government and industry have been looking more at oil and gas reservoirs as places to store the very carbon that was previously taken out of the reservoirs. 

One reason the process of storing carbon in underground rock layers, known as geologic carbon storage, holds appeal is due to the potential for such large amounts to be stored. In 2013, the USGS published a mean estimate of 3,000 metric gigatons of carbon storage potential in geologic basins throughout the country.  

For comparison, in 2021 the world emitted about 36.3 gigatons of carbon dioxide equivalent according to the International Energy Agency, and the United States emitted a net of about 5.6 gigatons according to the U.S. Environmental Protection Agency.  So the USGS estimate indicates that just under 83 years at 2021 levels of world emissions, or 536 years of U.S. emissions, could be stored geologically using currently available technologies. 

Geologic CO2 Sequestration Illustration Image
The use of carbon dioxide (CO2) injection for enhanced oil recovery (EOR) can prolong the productivity of many oil reservoirs and increase the U.S. hydrocarbon recoverable resource volume.

Geologic carbon storage is often described as a transition technology to decarbonize the oil and gas industry because it can be used alongside the existing production of oil and gas through a process called enhanced oil recovery. Producers inject carbon dioxide into oil reservoirs to increase oil production in areas that have already produced a lot of oil.  

The process works by pressurizing the carbon dioxide into a liquid, then pumping it into the rock layers to mix with the remaining oil left after initial oil and gas production. The resulting carbon dioxide and oil mixture can then flow to the well to be produced. Once the carbon dioxide is injected into the rock formations, some of it will remain trapped either by the rock itself or by dissolving into groundwater and any remaining oil in the reservoir.  

To explore the potential for pairing enhanced oil recovery with geologic carbon storage, the USGS has completed a national assessment of the technically recoverable oil resources and potential carbon storage if carbon dioxide-enhanced oil recovery technologies were used wherever feasible. Doing so could lead to an increase of about 29 billion barrels of technically recoverable oil resources, while storing about 8.4 metric gigatons of carbon, according to new USGS publications.  

Image shows a drill rig and vehicles near a road at dawn
USGS researchers drill a research well located on the south side of U.S. 90, 7.1 miles east of Brackettville, Texas. This core was drilled by USGS during field work for an oil and gas assessment for the Eagle Ford of the Gulf Coast Basins, one of the regions with the highest potential for both geologic carbon storage and enhanced oil production.

For comparison, in 2021, the United States produced about 4.1 billion barrels of oil and emitted 5.6 metric gigatons of carbon dioxide, according to the U.S. Energy Information Administration. 

“There is a lot of interest in carbon dioxide-enhanced oil recovery as an approach to reduce greenhouse gas emissions associated with ongoing oil and gas operations,” said Sarah Ryker, USGS associate director for energy and mineral resources. “In addition, this approach could demonstrate the potential for providing long-term carbon dioxide storage for other industries in the future as well. This USGS research helps quantify that potential.” 

The West Texas and Eastern New Mexico region and the Gulf Coast region together have 60% of the mean assessed carbon dioxide enhanced oil recovery oil potential and 61% of the mean assessed carbon dioxide storage potential. Other regions with significant oil resource and carbon dioxide storage potential include the Midcontinent region and Rocky Mountains and Northern Great Plains region. These regions have excellent geological conditions and oil reservoirs that are suitable for carbon dioxide enhanced oil recovery. 

“The National Petroleum Council federal advisory committee proposed a roadmap to help the United States store about 0.5 gigatons of human-produced carbon dioxide in geologic formations annually, and this work shows the potential to store a total of 14-19 times that through enhanced oil recovery alone, using today’s technologies,” said Ryker. “Of course, as this estimate is just for enhanced oil recovery and only using today’s technology, future technologies and industrial applications may create even greater potential for geologic carbon storage as a method for long-term emissions abatement.” 

This research is part of a broader USGS effort looking into how geology can aid in storing greenhouse gases. In addition to geologic carbon storage, the USGS has published studies on carbon mineralization and carbon emission and storage potential on Federal lands. 

Technically recoverable resources are those that are estimated to exist based on geologic, geophysical and geochemical information for the assessed rock layers, and that can be produced using today’s standard industry practices and technology. These are different from economic reserves, which are those quantities of oil and gas that can be produced profitably. 

These assessments were conducted based on a peer-reviewed, publicly available methodology for assessing technically recoverable resources and can be found here. To find out more about USGS energy assessments and other energy research, please visit the USGS Energy Resources Program website and follow us on Twitter

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