What is Carbon Dioxide Enhanced Oil Recovery (CO₂ EOR)?

Carbon dioxide enhanced oil recovery (CO₂ EOR) is a technique used to extract oil left underground following conventional oil drilling operations. CO₂ is injected into an oil reservoir, where it serves to mobilize residual oil. Following CO₂ EOR operations, the CO₂ can remain underground, in the reservoir, and thereby be prevented from entering the atmosphere. CO₂ EOR can extend the productive life of an existing oilfield by several decades, and it can lead to recovery of millions of barrels of additional oil.

How it Works
Under suitable temperature and pressure conditions, CO₂ is mutually soluble with the crude oil in a geologic reservoir. This means that injected CO₂ is able to dissolve and displace oil residue that is trapped in rock pores, just as a solvent is able to displace grease from a dirty bicycle chain. In a typical CO₂ flood operation, a pipeline delivers CO₂ to the oilfield, where it is directed to injection wells. These wells are strategically placed to optimize the areal sweep of the CO₂ through the reservoir. As the injected CO₂ moves through pore spaces in the rock, it encounters residual crude oil. The crude oil mixes with the CO₂, forming a concentrated oil bank that is swept to producing wells. In this way, oil and gas companies are able to gain access to oil that would otherwise be left in the ground.

Background on CO₂ EOR
CO₂ EOR was first tested in the early 1970s in West Texas. Since then, it has been utilized successfully throughout the Permian Basin of West Texas and eastern New Mexico. It is currently being used in oilfields in Kansas, Mississippi, Wyoming, Oklahoma, Colorado, Utah, Montana, Alaska, and Pennsylvania. In the United States, there are currently 13,000 CO₂ EOR wells in operation that produce a total of about 245,000 barrels of oil per day. Industry experts estimate that we have the potential to produce over 40 billion barrels of additional oil from existing domestic fields using advanced CO₂ EOR techniques.

Industrially-Sourced CO₂
Until recently, most CO₂ EOR has depended on naturally-occurring underground deposits as the source of the CO₂. In recent years, however, industry has begun to utilize CO₂ that has been captured as a by-product of fossil fuel combustion, gasification, or other industrial processes. Because a ton of CO₂ costs $30, and each ton can yield 2-3 barrels of oil, there is a strong economic incentive to re-use industrially- sourced CO₂ from gasification plants, gas processing facilities, and power generation plants.

Benefits
CO₂ EOR represents a win-win strategy for beneficial use of industrially-sourced CO₂. From an economic standpoint, CO₂ EOR is a highly effective tool for re-invigorating oil production from mature fields that might otherwise be abandoned. From an environmental standpoint, it represents a practical way to recycle and utilize CO₂ while reducing overall atmospheric CO₂ emissions.

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