The gas industry justifies the benefits of extracting shale gas by drilling and hydraulic fracturing (fracking) in terms of providing energy, economic stimulation and jobs. Also, some landowners have benefited by earning income from gas leases and royalties.
However, other landowners claim that, subsequent to nearby drilling and fracking, their drinking-well water became contaminated by flammable gas. Gas industry representatives dismiss the claim that fracking might make drinking water flammable.
Lighting water on fire "is a parlor trick that really has nothing to do with hydraulic fracturing," said Jim Smith, a spokesman for the Independent Oil and Gas Association of New York State in a Wall Street Journal report. Instead, he said, it's caused by naturally-occurring methane that gets into some water supplies regardless of whether there's nearby drilling.
Despite such gas industry claims, there was no scientific evidence as to whether or not contamination of drinking water with natural gas is linked to nearby drilling and fracking. But there is now.
Scientists at Duke University measured the dissolved gas levels in 60 drinking water wells in the Marcellus and Utica shale drilling areas in northeastern Pennsylvania and southern NY state. In a paper published recently in the Proceedings of the National Academy of Sciences, they reported that water samples taken closest to the gas wells had an average of 17 times higher than the methane levels detected in water samples taken further from active drilling. The maximum level was 58 times higher (see graph, below). Methane is the major component of natural gas. The average methane level detected was in the range of "action levels for hazard mitigation" recommended by the U.S. Office of the Interior (graph, large gray rectangle), and many water wells had levels far above that range.
Some Pennsylvania homeowners whose wells became contaminated after nearby drilling and fracking had demonstrated earlier that their well water contains flammable gas.
At recent presentations on shale drilling and hydraulic fracturing sponsored by the Geology Department at the University at Buffalo, some of which are now available online, several speakers representing the gas drilling industry stated emphatically that the ability to light well water on fire is due to biogenic methane, i.e., methane produced on the surface of the ground by bacteria (e.g. gas from swamps, bogs, rotting plants).
Industry representatives also claimed that flammable water is not due to thermogenic methane, i.e., methane produced deep underground in the shale millions of years ago from decomposition of buried organic matter at high temperature and pressure.
But neither of these gas industry claims are backed by scientific studies on the water wells in Pennsylvania. So which type of methane is responsible for the high concentrations in drinking-well water? Is it biogenic methane present at the surface, or thermogenic methane present deep underground in the shale?
