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Captured carbon has been used for Enhanced Oil Recovery (EOR) by the petroleum industry for decades and currently utilizes around 70% of all CO₂ captured

Summary​

Enhanced Oil Recovery (EOR) using carbon dioxide has been employed for decades to extract additional oil from reservoirs. CO₂ injection helps recover 5% – 15% of original oil reserves after primary extraction, with most captured CO₂ coming from gas processing. While promoted as carbon storage, lifecycle analysis shows CO₂-EOR offsets only 6% – 56% of emissions due to energy-intensive capture processes. Over 136 US projects existed in 2014, but the method's climate benefits remain limited despite technical improvements.

Carbon dioxide captured from industrial processes like Carbon Capture and Storage (CCS) can be used for Enhanced Oil Recovery (EOR) by the petroleum industry. For a typical oil field, the first recovery of the original oil-in-place (OOIP), which relies on the natural pressure of the reservoir, is between 5%-20%. Secondary recovery, which relies on the injection of water or natural gas into the reservoir, can generally yield between 20% – 30% of the OOIP 1. As there is still around half of the OOIP left in the reservoir after secondary recovery, the petroleum industry has developed EOR methods to increase the recovery of the remaining oil. Some of these include thermal methods, chemical methods, and miscible displacement methods, which is where CO₂ EOR comes in. EOR should not be confused with fracking, as the process of fracking is considered a primary recovery method as it allows access to oil reservoirs that wouldn't otherwise be accessible. Globally, approximately 70% of all CO₂ captured is from gas processing plants for use in EOR 2.

The process of CO₂ EOR involves injecting CO₂ or a mixture of water and CO₂ into the reservoir. Once in the reservoir, the CO₂ first displaces the oil, then it dissolves into the oil, forming a single homogeneous phase, which in turn reduces the oil's viscosity, allowing the oil to flow more easily to the production well. This is known as the miscible mode of EOR 1. This process of homogeneous mixing relies on specific temperatures and pressures, and when those are not met, homogeneous mixing does not occur. However, even when non-homogeneous mixing occurs, the presence of CO₂ in the oil phase can still reduce oil viscosity and increase the recovery factor of the oil field, a process known as the immiscible mode of CO₂ EOR 1.

The recovery effectiveness of current best practice CO₂-EOR is typically between 5% - 15% of the OOIP, with future improvements to the technological process expected to increase this to above 20% 1. In 2014, there were over 136 operating CO₂ EOR projects in the United States, which have injected over 3 billion cubic feet or 156,000 tons of CO₂. However, it should be noted that most of this CO₂ was captured from natural gas processing and not from CCS due to high CCS costs 3 4. The petroleum industry has heavily pushed the idea that CO₂-EOR can be a way of long-term storage of CO₂, creating 'carbon-negative' oil fields by offsetting the emissions from the combusted oil by the EOR carbon storage. However, lifecycle analysis of combined CCS and CO₂-EOR shows a net maximum storage efficiency of between 6% - 56%, meaning that the EOR storage can only offset a maximum of around half the CO₂ emissions produced in a best case scenario 3. This is primarily due to the large energy requirements in capturing carbon dioxide from a source through CCS, which produces between 0.43–0.94 kg of CO₂ per kg of CO₂ stored depending on the energy mix of the CCS process 3.

Sources​

Footnotes​

  1. Verma, M. K. (2015). Fundamentals of carbon dioxide-enhanced oil recovery (CO₂-EOR)—A supporting document of the assessment methodology for hydrocarbon recovery using CO₂-EOR associated with carbon sequestration (U.S. Geological Survey Open-File Report 2015–1071). U.S. Geological Survey. https://doi.org/10.3133/ofr20151071 ↩ ↩2 ↩3 ↩4

  2. Abdulla, A., Hanna, R., Schell, K. R., Babacan, O., & Victor, D. G. (2020). Explaining successful and failed investments in U.S. carbon capture and storage using empirical and expert assessments. Environmental Research Letters, 16(1), 014036. https://doi.org/10.1088/1748-9326/abd19e ↩

  3. Farajzadeh, R., Eftekhari, A. A., Dafnomilis, G., Lake, L. W., & Bruining, J. (2020). On the sustainability of CO₂ storage through CO₂-enhanced oil recovery. Applied Energy, 261, 114467. https://doi.org/10.1016/j.apenergy.2019.114467 ↩ ↩2 ↩3

  4. International Energy Agency. (2019, April 11). Can CO₂-EOR really provide carbon-negative oil? IEA. https://www.iea.org/commentaries/can-co2-eor-really-provide-carbon-negative-oil ↩