Rice University scientists have performed a detailed analysis of water produced by hydraulic fracturing of three gas reservoirs and suggested environmentally friendly remedies are needed to treat and reuse it. Water ‘produced’ during shale gas extraction is highly saline, radioactive, and potentially can contain species of bacteria that may prove invasive. As such, produced water is a source of one of the biggest environmental hazards associated with shale exploration.
In a new study called Environmental Science: Processes and Impacts, funded by The Robert A. Welch Foundation and the Welsh Government Sêr Cymru Program, researchers advocate a more advanced recycling of produced water than the current methods of disposal.
The amount of water used in shale exploration is staggering, with 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. This, said Rice chemist Andrew Barron, can place a considerable burden on nearby communities.
Barron noted that shale gas wells, the focus of the new study, make most of their water within the first few weeks of production. After that, a few barrels a day are commonly produced. Environmental Protection Agency, however, reached a different conclusion when it observed that wells tend to produce a higher percent of water as they age.
If the EPA estimates are correct, the problem of produced water will only grow in time. The need for finding an environmentally-acceptable way of disposing or – preferably – recycling the water is the more pressing.
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.”
While fracking fluids consist of 90 percent water with some proppants and anti-gelling agents, the produced water – the water that flows back from the shale well – is far more problematic.
The research has 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.
The current methods for recycling produced water include using chlorine dioxide or hypochlorite treatments. This, however, the research found enhance bacteria’s ability to convert naturally occurring hydrocarbons to chlorocarbons and organobromides.
“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,” – he added.
Another problem associated with produced water is the radioactivity of the matter brought back to the surface. The irradiated matter is known as TENORM – Technologically-Enhanced, Naturally-Occurring Radioactive Material – and with robust exploration and high volumes of produced water, TENORM occurs in such high quantities that it poses a huge problem when it comes to safe disposal.
TENORM from oil and gas drilling comes in many forms. Broken bits of mineral known as “drill cuttings” are created when a well’s hole is bored. Water that comes from the well, whether it’s pumped in or from a reservoir, picks up dissolved minerals on its way to the surface and is called “brine.” It can also create a muddy mix of saltwater and minerals called “sludge” or leave a residue called “mineral scale” on equipment.
In small quantities, TENORM can be treated to remove solid contaminants and reused for fracking. Solid radioactive material is encased in cement and stored in a landfill. With the scale of shale exploration in the U.S., however, the amount of radioactive material is huge.
So far, TENORM is a problem without a solution. Several companies have tried to send the radioactive sludge to landfills and have subsequently been banned from doing so. As a result some companies end up illegally dumping or stashing their TENORM. In March, for example, hundreds of garbage bags stuffed full of irradiated filter socks and other equipment were found stashed in an abandoned gas station in Noonan, ND.
The Pennsylvania Department of Environmental Protection is in the process of working on a study to look at naturally occurring levels of radioactivity in by-products associated with oil and natural gas development.
“This administration is undertaking what will be the most comprehensive study of its kind anywhere, and Gov. Corbett has directed us to do so in order to be proactive for the future and to continue Pennsylvania’s leadership in responsible development of domestic natural gas resources,” DEP Secretary Mike Krancer said.
“This thorough and rigorous study, which will focus on conditions here in Pennsylvania, is further demonstration that states are best suited to responsibly oversee the natural gas exploration and production activities taking place in our respective borders.
“DEP’s current regulations and monitoring networks are designed to protect the public from exposure to unsafe levels of radiation, and our regulations in this field have led the nation for years,” Krancer said.
The agency will collect samples of flowback water, rock cuttings, treatment solids and sediments at well pads and wastewater treatment and waste disposal facilities. The study will also analyze the radioactivity levels in pipes and well casings, storage tanks, treatment systems and trucks.
This certainly is a step in the right direction. Yet until the study is completed, no review of waste storage procedures is likely to be proposed, and the gallons of radioactive sludge will keep accumulating.
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