As drillers compete for access to water for their operations, researchers are looking for new ways to reuse and recycle wastewater for the good of the environment, as well as looking ahead to the possibility of more restrictions at the state or federal level that may be imposed on underground injection wells, according to Accenture.
The consulting firm’s researchers said in a report issued earlier in December that water access is likely to become “more of a constraint” for drilling operators, especially in arid areas and regions with seasonal water flow variations.
“In the United States, regulators have started to impose seasonal limits on volumes of water withdrawals via permitting restrictions in Pennsylvania,” wrote the authors in “Water and Shale Gas Development: Leveraging the U.S. Experience in New Shale Developments.”
“In drier regions, the competition for access to freshwater resources in particular areas will make water reuse more attractive. Logistics practices and wider water reuse will be key in addressing these concerns.”
Unconventional wells drilled using fracturing techniques sans water haven’t reached wide-scale use, but “operators are increasingly looking at alternatives to hydraulic fracturing [fracking], in addition to the use of proppants requiring less water for transport.”
According to Accenture, there are about 200,000 underground injection wells in the United States, and well permits remain “relatively easy” to obtain. However, if U.S. natural gas prices were to increase, as they are expected to, more drilling — and more injection wells — are likely, the researchers said.
Veil Environmental LLC President John Veil posited about a variety of wastewater treatment options already being used at different locations in U.S. shale gas plays.
“Water management choices have evolved steadily over time and will most likely continue to evolve,” he said. “Born out of necessity, several companies operating in the Marcellus Shale experimented with capturing the initial volume of flowback water, filtering it to remove suspended solids, then blending it with new freshwater to make up frack fluids for new wells.
“The early tests were positive and soon nearly all Marcellus flowback was managed in this way. This type of process works well on the large volumes of one-time flowback that are generated by each well,” and are less effective for managing low volumes of produced water that flow for months from each active shale gas well.
Other options, he said, are “simple processes,” which involve using a sock or bag filter for the wastewater, followed by reuse for future frack fluids. These processes are being evaluated in several domestic plays and offer possibilities for overseas unconventional plays, said Veil.
Other experimentation is under way to create “clean” brine treatments, he said. Because of the high levels of total dissolved solids in flowback and produced water, “these wastewaters are particularly challenging to treat to make freshwater. The chemical supply companies are actively working to develop new formulations that can function well at high salinity levels.”
Treatments to create “clean” freshwater also are being tested, along with evaporation, or crystallization.
In some arid locations, commercial disposal companies are using large ponds to evaporate flowback and produced water “passively,” Veil said. “In crystallizer systems, the entire volume of flowback and produced water is evaporated to a dry byproduct in a mechanical heating device.” Crystallizer systems are expensive, but “the advantage they offer is that there are no liquid byproduct streams.”
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