ice University scientists have produced a detailed analysis of water produced by hydraulic fracturing (aka fracking) of three gas reservoirs and suggested environmentally friendly remedies are needed to treat and reuse it.
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, said Rice chemist Andrew Barron, who led the study that appeared this week in the Royal Society of Chemistry journal Environmental Science: Processes and Impacts.
The amount of water used by Texas drillers for fracking may only be 1.5 percent of that used by farming and municipalities, but it still amounts to as much as 5.6 million gallons a year for the Texas portion of the Haynesville formation and 2.8 million gallons for Eagle Ford. That, Barron said, can place a considerable burden on nearby communities.
Barron noted that shale gas wells, the focus of the new study, produce most of their water within the first few weeks of production. After that, a few barrels a day are commonly produced.
The project began with chemical analysis of fracking fluids pumped through gas-producing shale formations in Texas, Pennsylvania and New Mexico. Barron and the study’s lead author, Rice alumnus Samuel Maguire-Boyle, found that shale oil and gas-produced water does not contain significant amounts of the polyaromatic hydrocarbons that could pose health hazards, but minute amounts of other chemical compounds led them to believe the industry would be wise to focus its efforts on developing nonchemical treatments for fracking and produced water.
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, Barron said.
“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, Barron said. Eight to nine percent of the fluid contains sand or ceramic proppant particles that wedge themselves into minute fractures in the rock, holding open paths for gas and oil to escape to the production well.