First scientific study of its kind -- Gas industry refuses to share data
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.
Methane in well water is both a safety and health hazard. The gas escapes from water at the tap, the shower head, the washing machine and into the air of homes, where it can become flammable and even explosive. Methane can also cause headaches, nausea, brain damage and, at very high levels, death by suffocation. Potentially dangerous levels of methane were found in well water near drilling sites in northeastern Pennsylvania.
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?
The Duke University scientists used established methods of chemical isotope analysis and additional methods to answer this question. Well-water samples obtained far from gas drilling showed only traces of biogenic methane. However, samples taken closer to drilling sites had elevated concentrations of thermogenic methane, i.e., gas derived from the shale layer where the drilling occurred. The finding of thermogenic methane, together with the proximity to the gas wells, indicated to the scientists that high-level methane contamination of drinking well water was linked to shale-gas drilling and fracking.
The identification of shale gas as the contaminant is consistent with the testimony of landowners in Pennsylvania who have indicated that their well water became flammable only after drilling and fracking of the shale began.
One of the authors, scientist Robert Jackson, said, "The most simple explanation, I believe, for what we saw involves leaky gas well casings. And that may have nothing to do with hydraulic fracturing. It could be, though, that the high pressures involved in hydrofracking are more likely to cause leaks in the gas well casings that protect the piping, the tubing, near the surface. So we really don't know the mechanism yet, and that's a definite area of future research."
The Duke report also showed that there are some water wells with a low-level of methane located close to gas drilling sites (see graph), suggesting that, in those cases, active gas drilling and fracking did not cause elevated methane contamination of the water.
The report concluded that greater stewardship, more data, and possibly regulation would be needed to ensure the sustainable future of shale-gas extraction and to improve public confidence in its use.
The gas industry has faulted the Duke scientific study because no data on methane concentrations in the well water prior to drilling were presented. “The authors admit they have no baseline data at all, which makes it impossible to characterize the state of those water wells prior to recent development,” said Chris Tucker, a spokesman for a coalition of independent gas producers.
In response to industry criticism, Dr. Robert Jackson said, “The industry is sitting on hundreds of thousands of pre- and post-drilling data sets. I asked them for the data and they wouldn’t share it." Others have confirmed the existence of extensive industry data.
Since 2008, when water contamination was suspected to be caused by shale drilling in Dimock, Pennsylvania, gas drilling companies, including Chesapeake Energy, Shell and Atlas, have been collecting water samples from private wells before they drill, according to several industry consultants. It is one of the largest collections of pre-drilling water samples in the country.
Jackson also indicated that his team will be taking samples to obtain more data, and they hope to collaborate both with industry and other research labs.
The gas industry has claimed repeatedly, without releasing any scientific evidence, that what they are doing is safe and that it does not contaminate drinking-water wells. Such unsupported statements made by the industry along with their refusal to share their data are not helping the gas industry win public trust.
As stated in their publication, the Duke University scientists believe that, based on their results and the litigious nature of shale-gas extraction, long-term coordinated sampling and monitoring of industry and private homeowners are needed.
The full paper published in the Proceedings of the National Academy of Sciences is available here (PDF).
The Duke University scientists have recommended more research into the medical effects of methane exposure and more study of the disposal of fracturing fluid and the brine waste that comes back up with it. Thus far, no evidence was found for contamination of water samples with brine or some known fracturing fluids. However, the industry has not disclosed the identity of all fluids used at each well.
The scientists also wrote a separate report entitled "Research and Policy Recommendations for Hydraulic Fracturing and Shale-Gas Extraction" that can be downloaded here (PDF).
Earlier posts about shale-gas drilling and fracking on this blog are here.