Researchers at Duke University have added their voices to the debate on hydraulic fracturing (fracking), saying in a report released Monday that the practice probably is not the cause of brine migration in the Marcellus Shale, but it could increase the potential for contaminating drinking supplies in the future.

The study of well water in northeastern Pennsylvania suggests that naturally occurring pathways could have allowed salts and gases from the Marcellus to migrate into shallow drinking water aquifers. The results are consistent with water-quality tests conducted in the aquifers in the 1980s, before rapid shale gas development began, according to Avner Vengosh, professor of geochemistry and water quality at Duke’s Nicholas School of the Environment.

In the Duke team’s evaluation of 426 samples from groundwater aquifers in six counties overlying the Marcellus in northeastern Pennsylvania, the locations of water samples containing brine did not correlate with the locations of shale gas wells, Vengosh said. But the geochemical fingerprint of the salinity detected in well water from the Lock Haven, Alluvium and Catskill aquifers suggests that a network of natural pathways may exist in some locations, especially in valleys, he said. Those pathways may have allowed gases and Marcellus brine to migrate up into shallow groundwater aquifers from deeper underground shale gas deposits.

“This could mean that some drinking water supplies in northeastern Pennsylvania are at increased risk for contamination, particularly from fugitive gases that leak from shale gas well casings,” Vengosh said.

Last year the team released a study that found high levels of leaked methane in well water collected near shale gas drilling and fracking sites in the Marcellus, but the researchers said there was no evidence that fracking fluids contaminated the water wells (see Shale Daily, May 11, 2011).

The new paper complements that study by showing “there are likely pathways through which methane and brine could flow,” Vengosh said.

“As shale gas exploration is becoming global — including in Poland, China, Australia and New Zealand — the take-home message of this study is that pre-drilling water quality monitoring is important for evaluating water quality baselines that can be used to detect future changes in water quality, and for evaluating possible hydraulic ‘short cuts’ and pathways between fluids and gases in deep shale gas formations and shallow aquifers,” said Vengosh. “Such geochemical reconnaissance would provide a better risk assessment for water contamination in newly developed shale gas exploration areas.”

The Duke researchers aren’t the first to enter the fracking debate. Earlier this year the Shale Resources and Society Institute (SRSI) at the University of Buffalo (UB) in New York released a study of data from the Pennsylvania Department of Environmental Protection (DEP), which concluded that fracking is becoming safer in the state’s Marcellus Shale, thanks at least in part to the state’s regulation of the practice (see Shale Daily, May 16). The results suggested that Pennsylvania’s regulatory approach has been effective at maintaining a low probability of serious environmental events and in reducing the frequency of environmental violations, the researchers said.

But the SRSI report contained “significant errors and distortions” that undermined its conclusions, according to an analysis released by the Public Accountability Initiative (PAI), a nonprofit research organization also based in Buffalo (see Shale Daily, May 31). Data in the report actually indicated that environmental risks increased between 2008 and 2011, according to PAI. And the report’s “pro-industry spin” was due to the “strong industry ties” of some of its authors and reviewers, PAI said.

Since the report was released, about 20 professors and students have formed the University at Buffalo Coalition for Leading Ethically in Academic Research to call for a university inquiry of SRSI. (see Shale Daily, July 2). UB has said it will not change the operations of SRSI, despite the controversy surrounding its report.

Cornell University researchers last year said methane emissions of flowback gas during completion of fracked wells are high enough to increase the greenhouse gas footprint of shale and tight gas to levels that exceed those of coal (see Shale Daily, April 13, 2011). The Cornell research was quickly challenged by a study published by the gas industry-supported American Clean Skies Foundation (see Shale Daily, April 21,2011), and other critics said the study overestimated the average volume of gas vented during well completion and flowback stages by 60-65% and overestimated the impact from emissions during well completions by up to 90%.