“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 Professor Andrew Barron (pictured), Sêr Cymru Chair of Low Carbon Energy and Environment at Swansea and the Charles W Duncan, Jr Welch Chair of Chemistry at Rice, who led the study published in the Royal Society of Chemistry’s journal Environmental Science: Processes and Impacts.

“The amount of water used by Texas drillers for fracking may only be 1.5 per cent 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,” said Professor Barron. “And that can place a considerable burden on nearby communities.

Professor Barron, who leads Swansea University’s Energy Safety Research Institute (ESRI), a £38 million investment which will be located on the University’s new Bay Campus, 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 study, funded through the Welsh Government’s Sêr Cymru Programme and The Robert A Welch Foundation in Texas, began with chemical analysis of fracking fluids pumped through gas-producing shale formations in Texas, Pennsylvania and New Mexico.

Professor Barron and the study's lead author, Rice University 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,” said Professor Barron.

"Ultimately, it will be necessary to clean produced water for reuse in fracking.

"In addition, there is the potential to recover the fraction of hydrocarbon in the produced water."

Fracking fluid is 90 per cent water, Professor Barron said. Eight to nine per cent 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.

The remaining one or two per cent, however, may contain salts, friction reducers, scale inhibitors, biocides, gelling agents, gel breakers and organic and inorganic acids. The organic molecules either occur naturally or are a residue from the added components.

The researchers found most of the salt, organic and other minerals that appear in produced water from shale gas reservoirs originate in the connate waters trapped in the dense rock over geologic time scales. These, they wrote, should be of little concern.

But they also found that produced water contained potentially toxic chlorocarbons and organobromides, probably formed from interactions between high levels of bacteria in the water and salts or chemical treatments used in fracking fluids.

Professor Barron said industry sometimes uses 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," said Professor Barron.

Primarily, he said, the researchers want their analysis to anticipate future problems as industry develops processes to remove organic compounds from water bound for reuse.

The new paper, Professor Barron said, should be of particular interest to international producers who are preparing to ramp up gas-recovery efforts in the UK, which recently announced plans to expand drilling, and other European countries.

"As the UK 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," he added.

Professor Andrew Barron, a professor of materials science and nanoengineering, is Sêr Cymru Chair of Low Carbon Energy and Environment at Swansea University and the Charles W Duncan, Jr Welch Chair of Chemistry at Rice University, Texas. He leads the Barron Research Group at Rice University, http://barron.rice.edu/Barron.html.

Notes:

Swansea University’s Energy Safety Research Institute (ESRI) is a £38 million investment which will be located on the University’s new Bay Campus. ESRI, the first research centre of its kind in the UK, concentrates the College of Engineering’s strength in the energy sector and focuses on the safety issues surrounding the development and expansion of existing energy processes, as well as the safe deployment and integration of new energy technologies. ESRI’s primary collaborator is BP. For more information on ESRI, visit http://www.swansea.ac.uk/campus-development/baycampus/informationonkeybuildings/energysafetyresearchinstitute/.

The ESRI is part of a new and growing international research and development consortium led by US-based eCORP Stimulation Technologies, LLC (ecorpStim) in Houston, Texas. The consortium brings together doctors and scientists from Texas’ Baylor College of Medicine and Rice University, Swansea’s collaborative partner the University of Grenoble, France, and Sheffield-based Glass Technology Services (GTS). Visit http ://www.swansea.ac.uk/media-centre/latest-research/swanseapartofgrowingworld-leadingenergyresearchanddevelopmentconsortium.php.