Plains CO2 Reduction (PCOR) Partnership
CO2 Flooding

CO2 flooding is the practice of injecting CO2 into oil reservoirs to recover additional oil. In the oil reservoir, the CO2 dissolves into the oil, makes it more mobile, and allows it to move more easily toward the production wells. In many cases, water is injected after the CO2 to help move the oil along. Since the 1970s, the injection of CO2 into aging oil reservoirs in West Texas has resulted in the production of more than 1 billion incremental barrels of crude oil.

The crude oil produced from a CO2 enhanced oil recovery (EOR) operation contains dissolved CO2. At the surface, the dissolved CO2 is separated from the oil, and the CO2 is then compressed and reinjected.

Each time CO2 is injected, some of the CO2 remains underground, permanently trapped in the oil-bearing rock formation. This trapped CO2 does not return to the surface in the produced crude oil.

To make up for the CO2 that remains trapped in the oil reservoir, the CO2 flood operator purchases additional CO2. The operator then combines this new CO2 with CO2 that the operator has separated from the crude oil. In this way, the proper amount of CO2 is available for injection into the underground oil reservoir.

EOR projects are designed to be active for decades, and each project has many cycles of CO2 injection. With each cycle, another portion of CO2 that is injected becomes permanently trapped in the reservoir. By the end of the flood, virtually all of the CO2 that has been purchased and brought to the field is permanently trapped or “sequestered” in the reservoir. As a result, hundreds of millions of tons of CO2 are currently trapped underground in oil fields in the United States and around the world.

Historically, most of the CO2 for oil field floods has come from natural underground accumulations of CO2. The CO2 from these geologic deposits is limited in volume, and economics restrict its use to within a couple of hundred miles of where it occurs. In contrast, anthropogenic (or human made) sources of CO2 are widespread. As more and more oil fields mature, the need for CO2 EOR will increase, and the potential for EOR using anthropogenic CO2 will increase as well. 1,2 EOR using anthropogenic CO2 represents a prime opportunity for reducing the CO2 emissions from large-scale sources like power plants, gas- and oil-processing plants, and ethanol facilities.

References
  1. Bradley, T., The CO2 enhanced oil recovery story: Kinder Morgan CO2 Company.
    docs.nrdc.org/globalWarming/files/glo_09031101c.pdf (accessed March 2010).
  2. National Resources Defense Council, 2008, Tapping into stranded domestic oil - enhanced oil recovery with carbon dioxide is a win-win-win. www.nrdc.org/energy/eor.pdf (accessed March 2010).