Duke University and the U.S. Geological Society (USGS)
investigated the possible degradation of water quality in shallow aquifers
overlying the Fayetteville Shale formation in north-central Arkansas, where
approximately 4,000 wells have been drilled since 2004 to extract
unconventional natural gas.
The study
which was released in mid-May 2013 found no evidence of groundwater
contamination from shale gas production in Arkansas. The scientists
sampled 127 shallow drinking water wells in areas overlying the gas-producing
Fayettevile Shale formation. The samples were taken at various locations
by personnel from the Arkansas Oil and Gas Commission. The samples were
analyzed for major and trace elements and hydrocarbons. Isotropic tracers
were used to identify the sources of possible contamination. The chemical
composition of any contaminants in the water samples was compared to those
found in gas samples from the nearby shale gas drilling sites. The
comparisons showed no spatial relationship between methane and salinity
occurrences in the shallow drinking wells located in proximity to the
sites. The low concentrations of methane that were found in the water did
not match the isotopic fingerprint of the methane in the gas samples in all but
two cases, showing that the methane in the water was primarily produced by
biological activity in the shallow aquifers.
The scientists concluded
that “systematic monitoring of multiple geochemical and isotopic tracers is
necessary for assessing the possible groundwater contamination in areas
associated with shale gas exploration as well as the possible hydraulic
connectivity between shallow aquifers and deeper production zones.”
The scientists indicated that variations in local and regional geology as
well as human factors, such as drilling techniques and the integrity of the
well bore, play major roles in determining the possible risk of groundwater
impacts from shale gas development and in preventing or allowing gas
leakage from drilling sites to shallow aquifers.
This article was prepared by Barclay Nicholson (barclay.nicholson@nortonrosefulbright.com or 713.651.3662) from Norton Rose Fulbright's Energy Practice Group.
