A Duke University study of wells near shale gas drilling sites in Fayetteville, Ark. shows no groundwater contamination. Low levels of methane found in samples were mostly from biological activity inside shallow aquifers, not from shale gas production contamination, scientists concluded.
Previous Duke studies of the effects of shale gas drilling in Pennsylvania found methane contamination in groundwater, but no signs of fracking fluids.
But the Duke scientists said that far from contradicting the previous studies, their latest research shows that varying geological factors and drilling techniques can determine whether gas leaks from a drilling site into shallow aquifers.
Shale gas production often involves the use of hydraulic fracturing, or fracking. In this process, gas companies pump water, sand and chemicals deep underground at high pressure, to crack open hydrocarbon-rich shale. A steep increase in fracking and a boom in shale gas production have been shadowed by concerns in recent years about water contamination by methane, fracking fluids and wastewater from the operations.
Scientists from Duke and the US Geological Society studied 127 samples of groundwater in north-central Arkansas and published their findings in the Journal of Applied Geochemistry. Using isotopic tracers to identify sources of potential contaminants, the researchers analyzed samples for major and trace elements as well as hydrocarbons.
They stressed that while their study was revealing, the environmental effects of fracking need to be further examined, and systematic monitoring is essential to evaluate possible groundwater contamination.
In March, Chevron, Shell and other natural gas companies and environmental groups formed the Center for Sustainable Shale Development, to set standards for fracking in the Appalachian Basin and work on reducing toxicity levels.
A research paper published by Ceres two weeks ago calls for fracking operations to use more recycled water in order to keep pace with projected shale gas growth, since shale gas production tends to occurs in states like Texas and Colorado where there are water shortages due to a prolonged drought.