Credit: Mark Zoback
Can fracking operations contaminate drinking water? Findings of recent geological studies generate many disputes on the safety claims of the hydraulic fracturing industry.
Hydraulic fracturing involves directing pressurized fluid onto deep shale of rocks to break them open in order to release the trapped methane gas inside. Geologists guauuuurantee this process will not contaminate the shallow aquifers that supply drinking water because there are several kilometers of rock that separates the fracking sites from the aquifers.
Avner Vengosh, from Duke University, says there is danger from another source. This source is a possible methane leak that poses a grave explosion risk.
Last year, his team claimed that drinking wells in Pennsylvania were contaminated with methane, possibly from nearby fracking operations. These claims were loudly criticized.
However, Vengosh reports new evidence of possible water contamination. Some 40 of 158 Pennsylvania aquifers analyzed by his team contained unusually high levels of salt.
These aquifers were contaminated with brine coming from salt aquifers at the same depth as fracking sites. Cracks in the rocks could have allowed the brine to travel hundreds of meters upwards. Methane gas could potentially travel the same way.
Mike Stephenson of the British Geological Survey says this process could take millions of years and does not present a serious problem.
Vengosh asserts, however, that the brine must be travelling upwards quite rapidly else the Pennsylvania heavy rainfall would wash it out of the shallow aquifers. He further asserts that a gas could move faster.
Richard Davies of Durham University proposes more possible ways for fracking to cause gas leaks. Boreholes that were not properly sealed can result to gas leaks. This could explain what happened in Dimock Pennsylvania, where residents are suing Calbot Oil & Gas Corporations for contaminating their drinking water. However, Calbot asserts that their test shows no water contamination in the area.
Davies argues that around 184,000 wells were drilled in Pennsylvania before records were kept. The locations of these wells are not known. If somebody operates near one of these sites, it could cause a gas leak.
A commercially funded study last December claimed that methane discovered in Pennsylvania aquifers had a different chemical signature from those released in the shale from hydraulic fracturing.
