An Underground Movement

An Underground Movement
Harnessing Carbon Dioxide for Energy and Environment

CO<sub>2</sub>There’s an abundant natural resource in this country that could reduce our reliance on imported oil and protect local jobs, while benefiting the environment—and it’s not ethanol. In fact, this exciting solution—carbon dioxide (CO2)—is usually cited in connection with environmental problems. But UAB engineering researchers are leading a project to see if the gas produced in industrial processes could help retrieve untapped oil from American fields.

“Traditional methods recover only about 40 percent of the oil that’s in the ground in most fields,” says UAB mechanical engineer Peter Walsh, Ph.D., the project’s director. After using a field’s own pressure and water injections to extract oil, it’s often not been economically feasible to recover any more. But the UAB-led project, which began earlier this year, is studying how to adapt the existing technique of CO2 injection to recover 10 to 20 percent more of a complex field’s vast remaining oil reserves.

Carbon dioxide makes oil easier to extract by thinning and pressurizing it—much as it puts the fizz in soda. It’s already being used to increase oil yields in places such as west Texas, eastern New Mexico, and Mississippi, Walsh says.

The field being tested in Citronelle, Alabama (near Mobile), offers special engineering challenges. “The Citronelle field has a somewhat complicated structure, and that’s where the research comes in,” Walsh says. “We’re applying CO2 enhanced recovery to a field more complex than any it has been applied to before.”

The Citronelle site could produce an additional 36 million barrels of oil, Walsh estimates. It has been active for more than 50 years and is the largest in the state; extending its working life could maintain local jobs for another 10 to 30 years, he says. The U.S. Department of Energy (DOE) predicts that nationwide, CO2 enhanced recovery could produce an additional two million barrels of oil a day by 2020.

The economic consequences of an improved CO2 extraction process could be enormous; so could the environmental impact. After all the oil has been extracted, CO2 can be safely injected back into the spaces where the oil was, Walsh explains. Ultimately, industrial CO2 that might otherwise be emitted could be “sequestered” in what amounts to an underground landfill. The site would be continually monitored for leaks.

The five-year, $6-million Citronelle project also includes three other universities in Alabama and North Carolina, the Southern Company, the Geological Survey of Alabama, and the DOE, which is funding half the project. UAB’s main research contribution will be creating visual simulations of the flows.

“The objective, ultimately, is to use CO2 from industrial sources in the entire process,” Walsh says, but for now, the project will recover oil with gas donated from a natural underground formation in Mississippi, owned by partner Denbury Resources, which also owns the Citronelle field; that CO2 will then be sequestered in the course of oil recovery. If all goes well, this technique could reduce the impact of modern industry on our fragile environment. According to a DOE study, depleted oil and gas fields around the world offer enough space to sequester 125 years’ worth of current CO2 emissions.

— Tara Hulen