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Sustainable Energy

Scrubbing Oil Wells Clean

A reversible surfactant could improve the yield of oil reservoirs.

With much of the easy-to-pump oil already extracted from U.S. oilfields, companies are increasingly going after the oil that remains stuck to the rocks in reservoirs. They typically inject steam or carbon dioxide into the reservoirs to thin the sticky oil so that it flows more easily. Researchers at Queens University in Ontario, Canada, have now found that a novel soaplike compound could make the process more productive.

The compound is a type of surfactant – a class of compounds that allow substances such as oil and water, which otherwise do not blend well, to form mixtures. Surfactants, which are used in materials such as detergents and paint, are widely known to increase oil production – by as much as 28 percent when pumped into reservoirs together with water, according to the U.S. Department of Energy. But they also pose a problem: once the oil-water emulsion is extracted from the reservoir, the oil needs to be separated. That’s complicated and expensive.

The biggest problem, says Eric Beckman, a professor of chemical and petroleum engineering at the University of Pittsburgh, is that the surfactant holding the oil and water together has to be deactivated. Currently, oil-water emulsions are broken using other chemicals or heat. “It would be much easier to simply turn the surfactant off,” he says, “so the emulsion simply falls apart and you can recover and reuse the surfactant if you want.”

This is exactly what Philip Jessop, associate professor of chemistry at Queens, made possible with the help of collaborators at Georgia Tech. They found a surfactant that they say can be switched on and off using carbon dioxide and air. Some companies have already expressed interest in the work, Jessop says. The researchers describe the novel properties of the surfactant, a type of amidine, in this week’s issue of Science.

You can pretty much “snap your fingers” and flip the amidine’s behavior, Jessop says. To make it act as a surfactant, all you have to do is bubble carbon dioxide through it; to deactivate it, simply flush out the carbon dioxide with air. “My students actually just take a balloon and fill it up with carbon dioxide, and then they empty that through the liquid. It’s that simple,” he says.

The improved surfactant could find a receptive market. The price tag of surfactants made them unpopular in the oil industry when crude-oil prices were less than $20 a barrel, says Gary Pope, director of the Center for Petroleum and Geosystems Engineering at the University of Texas at Austin. But now, as prices soar, many new oil-recovery projects that employ surfactants have started or are in the planning stages, he says. Surfactant injection, says Pope, is “one of the hottest enhanced oil-recovery methods at the moment and increasing exponentially.”

The cost of the amidine should be competitive with other surfactants, Jessop says. Even though he cannot put a specific price on the compound, the structure is very similar to that of compounds the oil industry already uses to reduce corrosion in wells. Another advantage for oil companies is that the process would not require any new equipment. “Oil recovery already uses carbon dioxide and surfactants,” Jessop says. “So they wouldn’t really have to change anything they’re doing except switch the surfactant.”

Still, the work is at an early stage, and much more needs to be done to make it practical, Jessop says. Moreover, he says, there is no guarantee that the surfactant would work in every oil field. Laboratory tests produced good results in only two of four crude-oil samples from different sources, he reports.

Nevertheless, Jessop hopes the technique could eventually be used to recover oil not only from reservoirs but also from oil sands. In Alberta, Canada, oil sands are known to hold vast amounts of crude oil, which is difficult to extract. Using the surfactant could help, Jessop says.

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