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Credit: Rice University |
More advanced recycling rather than disposal of "produced" water pumped back out of wells could calm fears of accidental spillage and save millions of gallons of fresh water a year, according to Rice University chemist Andrew Barron, who led a recent analysis of water produced by hydraulic fracturing (fracking), and how to treat and reuse it in environmentally friendly ways. The primary goal of the researchers is for their analysis to aid in anticipating future problems as industry develops processes to remove organic compounds from water bound for reuse.
The project began with chemical analysis of fracking fluids pumped through gas-producing shale formations in Texas, Pennsylvania and New Mexico. The researchers found that shale oil and gas-produced water does not contain significant amounts of the polyaromatic hydrocarbons that could pose health hazards, but does contain minute amounts of other chemical compounds that would make developing nonchemical treatments for fracking and produced water a good idea.
Currently, fracturing fluid pumped into a well bore to loosen gas and oil from shale is either directed toward closed fluid-capture systems when it comes out or is sent back into the ground for storage. But neither strategy is an effective long-term solution, according to Barron.
"Ultimately, it will be necessary to clean produced water for reuse in fracking," he said. "In addition, there is the potential to recover the fraction of hydrocarbon in the produced water."
Fracking fluid is 90 percent water; eight to nine percent of the fluid contains sand or ceramic particles that wedge themselves into minute fractures in the rock, holding open paths for gas and oil to escape to the production well.
Barron said industry may use chlorine dioxide or hypochlorite treatments to recycle produced water for reuse, but these treatments can actually enhance bacteria's ability to convert naturally occurring hydrocarbons to chlorocarbons and organobromides. The researchers suggested this transition could happen either downhole or in storage ponds where produced water is treated.
"We believe the industry needs to investigate alternative, nonchemical treatments to avoid the formation of compounds that don't occur in nature," Barron said. "As the U.K. and other European countries are looking to start hydraulic fracturing, it is important that they adopt best practices at the start, as opposed to evolving over time, as it has occurred here in the United States."
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