USGS: No Water Contamination From Drilling in Fayetteville Shale
The State Journal
10 January 2013
By Pam Kasey
A study examining the water quality of shallow domestic wells in
the Fayetteville Shale natural gas area of Arkansas found no
groundwater contamination associated with gas production, the
United States Geological Survey announced Jan. 9.
"This new study is important in terms of finding no significant
effects on groundwater quality from shale gas development within
the area of sampling," said USGS Director Marcia McNutt on
releasing the report, "Shallow Groundwater Quality and
Geochemistry in the Fayetteville Shale Gas-Production Area,
North-Central Arkansas, 2011." McNutt emphasized the survey's
hundred-year history of unbiased information on natural resources.
The Fayetteville Shale, like the Marcellus Shale, is an
unconventional gas reservoir that is exploited through horizontal
drilling and hydraulic fracturing. Drilling and production began
there in 2004, several years ahead of the Marcellus.
The scientists analyzed water quality data from samples taken in
Van Buren and Faulkner counties in 2011. They focused on chloride
concentrations from 127 wells and on methane concentrations and
carbon isotope ratios from a subsample of 51 wells.
Chloride is a naturally occurring ion that is found at elevated
levels in waters associated with gas production. It's a good
indicator of whether chemicals used during hydraulic fracturing
are reaching groundwater, the survey said in its media release.
Chloride concentrations from this study were not higher than
samples taken from nearby areas from 1951 through 1983. In
addition, chloride concentrations from wells within two miles of a
gas production well were similar to concentrations from wells more
than two miles from a gas production well.
Methane is the primary component of natural gas, but it also can
be found naturally in shallow shale formations in the Fayetteville
Shale area that are used as sources of water for domestic
supplies. Methane concentrations and carbon isotope ratios
indicated that almost all of the methane in groundwater samples
was naturally occurring as a result of biological processes in
shallow shale formations used as a source of water for domestic
purposes and did not originate from the Fayetteville Shale.
Groundwater chemistry in the shallow aquifer system in the study
area is a result of natural processes, the study's authors
"None of the data that we have looked at as part of this study
suggests that any groundwater contamination is resulting from
natural gas production activities," said USGS hydrologist Tim
"However, this study does not speak to other wells that were not
sampled, every chemical used during the hydraulic fracturing
process, or water quality changes that might take longer to
occur," Kresse acknowledged. "It does provide a baseline to use to
evaluate any possible changes in the future."