Duke study suggests Marcellus fluids can seep up into water supplies
Underground water supplies in some parts of Pennsylvania can be contaminated by fluid from the Marcellus shale, putting them at greater risk because of heavy gas drilling into that formation, according to a study released on Monday that critics challenged.
Duke University researchers found evidence that brine contaminated shallow aquifers in northeastern Pennsylvania after rising from the mile-deep rock layer. It probably followed natural pathways but if such seepage travels quickly, it could mean the billions of gallons of chemically treated water that drillers use to tap shale for gas could one day reach shallow groundwater, researchers said. “We don't have a good sense of what the actual timing is,” said Nathaniel R. Warner, a post-doctoral candidate who is the study's lead author. The study “is showing, importantly, that these pathways do exist. It becomes more important if we're talking about a short time frame.”
Drilling companies claim their threat to groundwater is minimized because the water sits above their targets, with thousands of feet of rock trapping any dangerous chemicals below.
The Duke study, which the National Academy of Sciences will publish, is the second one recently to suggest that fluid can migrate upward from deep shale layers. Natural faults and fractures in the Marcellus, made worse by drillers, could allow chemical migration to the surface within 10 years, hydrologist Tom Myers said in a work published in April in the journal “Ground Water.”
Penn State University geosciences professor Terry Engelder disputed both studies. He was one of the reviewers on the new Duke study and recommended the National Academy of Sciences reject the paper. The study doesn't address the time element, geologic pressure and absorptive rocks that would keep fluids trapped in or around the Marcellus, and the Marcellus had almost no fluid to begin with that could seep out, he said. “In terms of everything I understand about how the Marcellus behaves, that's not going to happen,” Engelder said.
The study found no correlation between the location of shale-gas wells and brine contamination from the Marcellus.
“This research demonstrates that freshwater aquifers in northeastern Pennsylvania have not been impacted by natural gas development activities,” said Kathryn Klaber, the group president.
Timothy Puko is a staff writer for Trib Total Media. He can be reached at 412-320-7991 or firstname.lastname@example.org.
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