Did you know that about 60 percent of the original oil in a petroleum reservoir is left underground after recovery using conventional technologies is complete?

Peter Walsh, left, looks at the terrain of the Mobile County Citronelle oil field along with Alan Shih, Gary Cheng, Richard Espisito of the Southern Company, and Theodorru Constantinos. Walsh is the principal investigator on an upcoming Department of Energy cost-shared project that will inject carbon dioxide (CO2) into the Citronelle oil reservoir in an effort to increase domestic oil production.

Peter Walsh, Ph.D., research professor in Mechanical Engineering, didn’t. “I thought they extracted almost all of the oil,” he says. “It turns out there’s often 50 to 70 percent of the oil that’s not recovered using standard methods.”

Extracting oil from a reservoir isn’t always easy – nor is it particularly cheap to do, especially in some terrains like those in South Alabama or in the Gulf of Mexico. Eventually, removing oil from any reservoir reaches a point where it’s not cost-effective to continue, and the majority of the oil remains below the Earth’s surface.

That’s where Walsh enters the picture: He is the principal investigator on an upcoming Department of Energy cost-shared project that will inject carbon dioxide (CO2) into a Mobile County oil reservoir in an effort to increase domestic oil production. The five-year, $6 million project is scheduled to begin Jan. 1, 2007.

“Injecting CO2 makes the oil swell, and, at sufficiently high pressure, oil and CO2 become a single fluid with lower viscosity than the oil by itself, which enhances its flow to the production wells,” Walsh says.

“The pressure at which CO2 and the oil from South Alabama form the homogeneous mixture is not known, so that’s one of the first things we’ve got to find out.”

The CO2 flood will take place in the Citronelle oil field in Mobile County. The Citronelle field is Alabama’s largest oil producer and is in what is known as the secondary stage of oil recovery, when water is being injected to push the oil out. Oil recovery using CO2 is known as tertiary, or enhanced, recovery.

Denbury Resources Inc., the owner and operator of the Citronelle oil field, is a partner in the project along with the Southern Company, the Geological Survey of Alabama, the University of Alabama, Alabama A&M University and the University of North Carolina at Charlotte. Gary Cheng, Ph.D., and Alan Shih, Ph.D., in Mechanical Engineering are co-investigators from UAB, working with Geologist Richard Esposito of the Southern Company and Dino Theodorou, both Ph.D. candidates in the Environmental Health Engineering Program.

Walsh says the team expects the injection of CO2 into the reservoir will significantly enhance oil recovery and extend the productive life of the oil field. It is estimated that 64 million barrels of oil could be recovered from the Citronelle field using the technique.

“It will be a great thing for the state of Alabama if the life of the field could be extended, because it not only means more oil could be extracted, but the people who work the Citronelle field could remain employed there for many more years,” Walsh says. “The field could continue to produce oil in a cost effective way for 10, 20, maybe 30 years.”

If successful, Walsh expects the yield for the Citronelle oilfield could improve by 15 to 20 percent. He says the improvement could be 10 to 20 percent at any oilfield, including those in the Gulf of Mexico, meaning total oil recovery could reach as high as 55 percent or more.

The project also will assess the potential for storing CO2 in the reservoir once the oil is depleted. The storage of CO2, also called carbon sequestration, is a hot topic because of rising concerns over possible global warming caused by increasing concentrations of greenhouse gases in the atmosphere.

“There’s no question that the CO2 concentration in Earth’s atmosphere is increasing, and temperatures have also been increasing,” Walsh says. “Some climate models show that the warming is consistent with the increase in CO2, but I don’t think that proves a cause-and-effect relationship. Still, that shouldn’t be an excuse for not trying to reduce CO2 emissions to the atmosphere. I hope that in addition to storage, we will develop the technology to recycle some of the CO2 produced in industrial processes.”

The CO2 to be injected during the Citronelle enhanced oil recovery project will come from a naturally occurring source in Mississippi and will be supplied by project partner Denbury Resources via pipeline.

Walsh says he hopes the CO2 used for future enhanced oil recovery will come from large combustion sources, such as coal and natural gas-fired power plants, and industrial processes such as cement plants, though their exhaust gases are not pure CO2. Technologies for capture of CO2 from large sources are not yet commercially available.

“We need to see how pure the CO2 should be for enhanced oil recovery,” Walsh says. “We need to find out how completely the CO2 must be separated from other combustion products, especially the nitrogen that comes along with oxygen when air is used to burn fossil fuels.”