Hydraulic fracturing uses pressurised fluid to crack open deep shale rocks to release the methane trapped within them. Geologists say this potentially harmful fluid is unlikely to percolate up through a few kilometres of rock to reach the shallow aquifers that supply drinking water – but Avner Vengosh of Duke University in Durham, North Carolina, thinks the methane itself could do so. The gas would be an explosion risk.
Last year his team claimed drinking wells close to fracking sites in Pennsylvania were contaminated with methane – suggesting that it has been released by fracking. About 40 of the 158 Pennsylvania aquifers his team studied were unusually salty, contaminated with brine from salt aquifers that occur at the same depth as fracking operations. Cracks in the rock must have allowed the brine to migrate hundreds of metres upwards. It is possible that gas from deep fracking operations could travel in the same way.
Mike Stephenson of the British Geological Survey points that the process is likely to take millions of years, making it far too slow to pose a serious problem . However, the salt water must be moving upwards fairly fast otherwise Pennsylvania's heavy rainfall would wash it out of the shallow aquifers. Gas would probably move even faster.
Residents of Dimock, Pennsylvania, are suing Cabot Oil & Gas Corporation for contaminating their wells. Residents in Dimock complained that hydraulic fracturing operations, or fracking, by Cabot near their homes had put methane in their water and endangered their health.
In a statement released on March 15, 2012, the EPA said its tests begun early this year found sodium, methane, chromium or bacteria, but at levels “within the safe range.” Two wells were found to have elevated levels of arsenic.
High levels of methane may have infiltrated private water wells and streams in Bradford County through small open spaces in a natural gas well that a drilling company was working to patch, state environmental regulators said Thursday. The description of the gas well failure was included in a letter from Department of Environmental Protection Secretary Michael Krancer to the Clean Air Council, an environmental group that commissioned a study last month that showed twice-normal concentrations of airborne methane in a roughly two-square-mile area of Leroy Twp. where the gas was found bubbling in streams and water wells.
Fracking is a process that injects water, sand and chemicals into deep shale formations to free trapped natural gas. Methane in aquifers located above the shale strata, for instance, in Pennsylvania, United States, has been attributed by some to be the result of contamination caused by the hydraulic fracturing process. If boreholes aren't properly sealed, gas can leak out of them. Around 184,000 wells were drilled in Pennsylvania before records were kept. Most of these probably aren't sealed, so if someone fracks near one the gas could escape up it. Last December an industry-funded study claimed that the methane in the Pennsylvanian aquifers was chemically different to that liberated from the shale during fracking.
Sources: Proceedings of the National Academy of Sciences, Oil & Gas Journal, Coalition for Healty County
Featured image: Whistle-blower Scott Ely holds up water from his aquifer in Dimmock (Credit: Michael Mullen)