A study funded by the National Science Foundation and U.S. Geological Survey, and conducted by Penn State University (PSU) researchers, found almost no methane contamination in groundwater sources near Pennsylvania oil and natural gas well sites. Most of the natural gas produced in the state comes from hydraulic fracturing.
The PSU researchers took 20,751 samples and found “possible” signs of methane contamination in only 17 or just 0.08 percent of samples.
“Of the 17 samples that came back positive for new methane, 13 came from the northeast,” a Penn State press release noted. “None came from sites within 2,500 feet of known […] wells. State law holds oil and gas companies responsible for methane leaks that affect wells within that 2,500-foot area.”
It should be remembered that methane in groundwater is a naturally occurring phenomenon in Pennsylvania and may not necessarily be the result of drilling activity. “It’s not uncommon to see methane in groundwater in the Marcellus Shale and other shale plays,” said Tao Wen, one of the study’s researchers. “Also, if methane had been in the groundwater for a long time, bacteria would have reduced the iron and sulfate. The reduced forms would have precipitated as iron sulfide, or pyrite.”
Another study conducted by the same researchers analyzed data from 11,000 groundwater samples taken from 1,385 natural-gas wells. The researchers found “no statistically significant deleterious impact on ten analytes related to the aggressive increase in development of unconventional shale-gas since 2008.”