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Engineers to design affordable carbon dioxide thickener to augment oil extraction

Tue, 10/16/2012 - 1:48pm

Crude oil extraction could be improved significantly and accessible domestic oil reserves could be expanded with an economical carbon dioxide thickener being developed by University of Pittsburgh engineers, thanks to a $1.3 million grant from the U.S. Department of Energy.

Current oil-extraction methods across the United States involve oil being "pushed" from underground layers of porous sandstone or limestone reservoirs using a first-water-then-carbon dioxide method known as the water-alternating-gas method. Carbon dioxide—which is obtained from natural carbon dioxide reservoirs and pipelined to oil reservoirs—is an ideal candidate for oil extraction given its ability to push and dissolve oil from underground layers of porous rock. However, its viscosity (or thickness) is too low to efficiently extract oil. As such, it tends to "finger" through the oil rather than sweep oil forward toward the production well. This process, "viscous fingering," results in oil production companies recovering only a small fraction of the oil that’s in a field.

During the late 1990s, a team at Pitt was the first to demonstrate that it was possible to design additives that could greatly enhance carbon dioxide's viscosity at low concentrations, although the compounds were both costly and environmentally problematic.

"The thickeners we developed years ago were too expensive for wide use," says principal co-investigator Eric Beckman, George M. Bevier Professor of Engineering in Pitt's Swanson School of Engineering. "So, in this proposal, we’re looking at designing candidates that can do the job at a reasonable cost."

Beckman and Robert Enick, principal co-investigator and Bayer Professor and Vice Chair for Research in Pitt's Department of Chemical and Petroleum Engineering, intend to build upon earlier Pitt models of carbon dioxide thickeners, but this time with a more affordable design that could cost only several dollars per pound. Ideally, their small molecule thickener would be able to increase the viscosity of pure carbon dioxide 100 times—something that hasn't previously been accomplished.

"An affordable carbon dioxide thickener would represent a transformational advance in enhanced oil recovery," says Enick. "More than 90% of carbon dioxide injection projects in the U.S. employ the WAG method to hinder the fingering of the carbon dioxide. However, if a thickener could be identified that could increase the viscosity of the carbon dioxide 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 carbon dioxide."

"It's clear there exists a very wide market for this type of carbon dioxide thickener," says 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."

This $1.3 million grant from the Department of Energy is through the National Energy Technology Laboratory under the category of "Unconventional Gas and Oil Technologies."

Source: University of Pittsburgh

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