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LEARN HOW TO STOP THE INVASIVE SPOTTED LANTERNFLY
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Updated: July 20, 2018
Penn State MCOR
As directional drilling and high-volume hydraulic fracturing have changed shale gas development, concerns over the release of methane and chemicals used in the process into groundwater has become an issue. A study done by Yale researchers looked at a time series of sampling groundwater with eight multi-level monitoring wells within an undrilled lease unit in Susquehanna County, Pennsylvania. Over the two-year study, groundwater samples were taken at 2 to 5-week intervals. During this period, seven horizontal wells were drilled, hydraulically fractured and producing from four well pads within the unit. While methane spiked in some water wells it was deemed to be due to natural variability, not drilling and fracking.
During drilling, pressures in hilltop monitoring wells near well pads abruptly dropped, then increased before returning to normal levels over a 24-hour period. An abrupt pressure jump occurred when a well casing ruptured, but methane concentrations in hilltop MWs never rose above 0.12 mg/L. For monitoring wells in valleys above gas well laterals, methane levels increased considerably over the course of the study period, but isotopic data, hydrocarbon compositions, and other evidence suggested that the methane did not come from the Marcellus Shale and was unlikely to be due to gas well drilling and hydraulic fracturing operations. Increased groundwater salinity with the increasing methane concentration indicated natural shifts in aquifer recharge that altered the mixing between methane-free shallow groundwater and naturally methane-rich deep groundwater.
The report can be found in the Proceedings of the National Academy of Sciences.