Study Aims for Improved Oil Extraction Methods Using CO2

(U.S. Department of Energy)

Engineers at University of Pittsburgh are studying new, more economical ways of extracting crude oil from older wells using carbon dioxide (CO2). The work of principal investigators Eric Beckman and Robert Enick is funded by a 1.3 million grant from the National Energy Technology Laboratory, part of the U.S. Department of Energy.

Older oil wells lose their natural pressure, and often leaving considerable amounts of crude oil in the ground. Current methods of extracting this extra oil from porous limestone or sandstone reservoirs use a combination of water and CO2 gas, called water-alternating-gas or WAG, to push the residual crude to the surface.

CO2 by itself would be a preferable extraction method, since the gas can push through the porous rock and dissolve the residual crude without water, but the viscosity of the CO2 is too low to move the oil. Instead the oil pokes through the oil, in a phenomenon called fingering, rather than pushing the crude to the production well. Researchers at Pittsburgh devised solutions in the 1990s to increase the viscosity of CO2, but they were found to be expensive and environmentally harmful.

Beckman and Enick propose starting with the earlier work, but creating a new process with a more affordable design. The researchers say a solution is feasible that would cost only several dollars per pound, yet still increase the viscosity of CO2 some 100 times.

Enick says if their research is successful it would represent a transformational advance in enhanced oil recovery. “More than 90 percent of CO2 injection projects in the U.S. employ the WAG method to hinder the fingering of the CO2,” says Enick. “However, if a thickener could be identified that could increase the viscosity of the CO2 to a value comparable to that of the oil in the underground layers of rock, then the fingering would be inhibited, the need to inject water would be eliminated, and more oil would be recovered more quickly using less CO2.”

“It’s clear there exists a very wide market for this type of CO2 thickener,” adds Beckman. “It’s been long recognized as a game-changing transformative technology because it has the potential to increase oil recovery while eliminating water injection altogether.”

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