Enhanced oil recovery is a step toward large-scale carbon capture and sequestration -- if done right.
Officials from the Department of Energy have affirmed that, despite the failure of Congress to pass climate legislation, DOE is still committed to advancing Carbon Capture and Sequestration (CCS), which many experts believe will be a critical technology for reducing carbon emissions and stabilizing the climate. Absent a price on carbon, however, DOE is expanding the acronym and its focus to CCUS – Carbon Capture, Utilization, and Sequestration.
An existing and profitable use of carbon dioxide being touted by DOE is enhanced oil recovery (EOR). In CO2-EOR operations, carbon dioxide is injected into aging oil fields to sweep out oil that would otherwise be unrecoverable. But at properly selected, operated, and monitored sites, EOR can not only utilize but also permanently sequester CO2.
DOE estimates the technical storage capacity offered by “next generation” CO2-EOR in the United States to be 45 billion metric tons of CO2 – roughly 21 times the 2009 U.S. CO2 emissions from coal and natural gas fired power plants. Perhaps surprisingly, EOR potential in most oil producing regions has been significantly limited by a lack of available carbon dioxide. Most of the CO2 used in current EOR projects comes from natural sources, but these sources are limited. Capturing anthropogenic CO2 from power plants can provide a large new source of CO2, spurring development of more projects combining EOR and geologic sequestration (GS). EOR + GS can in turn be a stepping stone for larger-scale CCS by helping to offset the CO2 capture costs and build necessary infrastructure.
But in order to ensure sequestration, EOR must be done right. Sites must be carefully chosen to ensure that they are suitable for geologic sequestration. Any potential migration pathways for CO2 to reach groundwater or the atmosphere must be identified, mitigated when possible, and avoided when not. Existing wells must be repaired as necessary and new wells must be constructed to prevent the migration of CO2. Projects must be monitored to track the movement of CO2 and determine that injection is proceeding according to plan. This monitoring must continue after injection ceases and until the CO2 has stabilized.
EPA has created a pathway for secure geologic sequestration of CO2. Some operators of EOR projects have balked at these new regulations, claiming they can’t work for EOR and will be too expensive, without explaining what exactly is too burdensome. In fact, many EOR operators may already be going above and beyond what is required by EOR “business as usual” regulations, but the public cannot be assured of this unless operators agree to adhere to the more comprehensive GS regulations. The precise differences between regulations for EOR versus GS are a topic for another blog, but suffice it to say that those written specifically for GS address the unique nature and challenges of the long-term storage of CO2 while those written for EOR do not.
EOR is a promising pathway to large-scale deployment of CCS, and this promise must not be jeopardized by cutting corners. It can and must incorporate both the utilization and sequestration of carbon dioxide and be performed only where appropriate and to the highest standards.