In contrast to work in PA, Duke/USGS study finds no groundwater issues in Arkansas #fracking regions. Main conclusions:
• Methane in groundwater is low and likely associated with shallow aquifer processes.
• No relationship between methane and salinity in groundwater and shale-gas wells.
• δ13CCH4 and δ13CDIC suggest biogenic origin for dissolved methane.
• Water- aquifer rock interaction controls majority of water chemistry.
More from Duke U. news release:
Previous peer-reviewed studies by Duke scientists found direct evidence of methane contamination in drinking water wells near shale-gas drilling sites in the Marcellus Shale basin of northeastern Pennsylvania, as well as possible connectivity between deep brines and shallow aquifers, but no evidence of contamination from fracking fluids.
“The hydrogeology of Arkansas’s Fayetteville Shale basin is very different from Pennsylvania’s Marcellus Shale,” [Avner] Vengosh noted. Far from contradicting the earlier studies, the Arkansas study “suggests that variations in local and regional geology play major roles in determining the possible risk of groundwater impacts from shale gas development. As such, they must be taken into consideration before drilling begins.”
Human factors — such as the drilling techniques used and the integrity of the wellbores – also likely play a role in preventing, or allowing, gas leakage from drilling sites to shallow aquifers, Vengosh said.