New Studies Show No Link Between Hydraulic Fracturing and Groundwater Contamination
A new study published in the Proceedings of the National Academy of Sciences found no evidence that fracturing shale causes groundwater contamination. A team of researchers from Ohio State University, Duke University, and the University of Rochester analyzed hydrocarbon and noble gas isotopes in groundwater near the Marcellus and Barnett shale formations to trace the source of 133 reported cases of contamination. The team identified eight clusters of fugitive-gas-contaminated groundwater, and found that each of the clusters was attributable to either a failure of annulus cement, faulty production casings, or well failure. The team did not find any evidence to suggest that a vertical migration of hydrocarbon gas from depth to groundwater through intervening layers of geological formations had occurred at any of the eight clusters. Thus, none of the contamination was due to hydraulic fracturing or horizontal drilling techniques.
The study shows that hydraulic fracturing and horizontal drilling techniques do not result in increased risk of groundwater contamination, and can be performed safely as long as wells are well-built and maintained. Thomas H. Darrah, who led the study, said that the “data clearly shows that the contamination in these clusters stems from well-integrity problems.” He added that “most of the issues we have identified can potentially be avoided by future improvements in well integrity.” Avner Vengosh, one of the study’s co-authors, said the results “rule out the possibility that methane has migrated up into drinking water aquifers because of horizontal drilling or hydraulic fracturing, as some people feared.”
The U.S. Department of Energy (“DOE”) also conducted a study that examined, among other things, whether gas or fracking fluids can migrate vertically to contaminate groundwater above depth during or after hydraulic fracturing operations. The DOE released its results on the same day as the Ohio State University study and similarly found no evidence of gas or fluid migration from shale to groundwater.
These results confirm a separate, Stanford University-sponsored study published in August. That report synthesized 165 academic assessments of environmental impacts associated with unconventional drilling and found that “surveys of groundwater contamination suggest that most incidents originate from the surface, including faulty wells, wastewater disposal, and spills and leaks from surface operation.” While the Stanford study made no particular policy recommendations, its authors suggested that contamination could be addressed through pre-drilling baseline studies with a particular focus on surface and near-surface activities.
This makes sense. Hydraulic fracturing typically occurs thousands of feet beneath the water table. Aquifers and wells are separated from fractured shale rock formations by thick layers of impermeable rock, which is how aquifers are formed in the first place; indeed, the DOE study also assessed the maximum height of the fractures associated with hydraulic fracturing operations in the Marcellus Shale, and found that the fractures did not impact a producing gas zone in between the shale and the near-surface zones containing groundwater. It stands to reason that contamination would be caused by leaks from the vertical shafts of the wells that traverse drinking water sources.
While producers and others familiar with the shale gas industry will not be surprised by these studies, they help to dispel claims that the hydraulic fracturing process poses significant risks to groundwater. To be sure, producers and regulators recognize that water contamination is a serious issue, and both have taken steps to reduce groundwater impacts from shale development. Producers regularly ensure that proper cement and steel casing are used in their wells. They also monitor well pressures during construction and completion. Likewise, many states have recently revised their well-integrity standards. Pennsylvania and Texas strengthened their regulations in 2010, and eight other states have followed suit in the past 18 months.
Further research efforts may also inform future improvements to well integrity practices for hydraulic fracturing operations. For instance, the Stanford University-sponsored study identified several areas for further research, including whether hydraulic fracturing and horizontal drilling practices lead to greater stresses on the well components, such as steel and casing cement, that ensure well integrity.
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Posted at 9/26/2014 11:53 AM