A multiyear study of water wells in rural areas during intensive development in the Utica Shale found that some had high levels of methane (CH4), but chemical testing showed that the development was not the source of the gas.
Based on the carbon isotopes identified in the well-water samples collected by researchers, the methane was from shallower depths. This biogenic gas likely was produced by bacteria in places such as the soil and in coal seams, according to the study in the June 2018 issue of the journal Environmental Monitoring and Assessment.
There are "production-scale coalbed CH4 reserves in the study area but no active coal bed gas wells," it said.
That finding contradicts the arguments of fracturing opponents who say hydraulic fracturing leads to methane contamination of groundwater aquifers. The movie Gasland famously dramatized the claim by igniting gas from a flowing faucet.
An author of the report, Amy Townsend-Small, director of environmental studies and associate professor at University of Cincinnati, cautioned that “this study represents a very small number of groundwater wells, and a small geographic area” compared with the huge scales of unconventional development. Other studies have concluded that groundwater was affected by fracturing but have not combined testing from the start of development and isotope identification.
The Utica study found concentrations in three locations that “had CH4 levels posing a fire or exploration hazard in enclosed spaces (above 10 mg/L).” Those represented a small percentage of the 180 groundwater samples collected, according to the paper done by scientists from the University of Cincinnati, the University of California at Irvine, and Indiana University in Bloomington.
Researchers also collected multiple samples at many wells, some from the earliest days of unconventional development in those counties allowing them to establish base levels of gas and observe any changes over time. They collected from 2–8 samples over time from 24 wells. Those represented 118 of the 180 samples tested.
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