Partners Only

Kids

Educators

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).