The use of carbon dioxide (CO2) in enhanced oil recovery (EOR) operations has been utilized by oil and gas companies for decades and breathed new life into the Permian basin in the 1980s. Since then, CO2 EOR projects have cropped up in Oklahoma, Wyoming and other states. Typically, these projects have been utilized to coax more oil out of mature oil fields where the formation has lost its pressure over time, thereby extending decline curves on older wells. Recently, however, CO2 is being used in newer as well as older wells in Montana and North Dakota.
The Bakken oil wells present their own unique challenges. While the typical vertical well often has a primary recovery rate of 15 to 20 percent of its available oil, a Bakken well may be able to produce only 4 to 6 percent of the reservoir’s oil. Moreover, while producers can usually use water flooding to pick up another 15 to 20 percent of a reservoir’s oil in conventional wells, water flooding is unlikely to be as successful in the Bakken given the depth of the horizontal wells and the tight nature of the shale rock.
According to research by the Energy and Environmental Research Center, between 4 and 6 percent of oil is now recoverable from the Williston Basin, but if CO2 enhanced recovery could aid in production of even an additional 1 percent, that would equal 2 to 9 billion additional recoverable barrels of oil. Thus, using carbon dioxide has the great potential to increase ultimate recovery from the Bakken over production from conventional methods.
Moreover, with the recent push to inject greenhouse gases into wells deep into the earth—a process sometimes called carbon capture and storage or CCS—more and more incentives and innovations seem to be cropping up. For example, companies such as General Electric Co. are researching the possibility of using CO2 instead of water in fracking operations. Such a change is unlikely to happen any time soon as fracking using CO2 is costly and generally requires additional infrastructure. In addition, there are still a host of technical and safety challenges to overcome. Nevertheless, the impressive results of CO2 EOR projects has been well documented, and this technique is no longer limited to application in mature oil fields.