A new study of possible hazards from hydraulic fracturing (fracking) for natural gas extraction was published today on the site of the Proceedings of National Academy of Sciences. The study, which appears to have been thorough, has both good and bad news for those, like me, who believe that natural gas has a huge role to play in our energy future. Obviously we need to pay attention to all the news, not just the part we like. The good news doesn't need mitigation; the bad news requires at least further investigation and perhaps mitigation. In the words of the authors: "We conclude that greater stewardship, data, and—possibly—regulation are needed to ensure the sustainable future of shale-gas extraction and to improve public confidence in its use."
The study by Stephen G. Osborn, Avner Vengosh, Nathaniel R. Warner, and Robert B. Jackson found no evidence that the fluids injected deep underground for fracking are leaking into nearby water wells; that's the good news. However, they did find concentrations of methane (eg. natural gas) that were much, much higher in water wells near natural gas wells (fracked and unfracked) than in other water wells in the same geological formations which are not located near sites where there has been drilling for natural gas. Although methane in drinking water, which can and does occur naturally, is not classified as a health hazard, it was found in concentrations which could pose a fire hazard in wells near drilling sites. The authors are scrupulous in drawing a distinction between naturally occurring methane in the local groundwater and that which is probably the result of drilling; they analyze both the chemical nature of their samples and use valid statistical techniques for concentrations found near and far from drilling.
Back to the good news for a minute. The authors tested for both upward migration of the chemicals used in fracking and for pressure from fracking forcing existing fluids up through the bed rock into the aquifer. They point out that there is typically one to two kilometers of rock between the formations which contain the natural gas and the deepest water wells; however, there is cracking from past seismic activity, so it was worth looking for possible seepage. There wasn't any.
So how did the methane get into the wells? Here's their answer:
"Methane migration through the 1- to 2-km-thick geological formations that overlie the Marcellus and Utica shales is less likely as a mechanism for methane contamination than leaky well casings, but might be possible due to both the extensive fracture systems reported for these formations and the many older, uncased wells drilled and abandoned over the last century and a half in Pennsylvania and New York [where they did their study]… More research is needed across this and other regions to determine the mechanism(s) controlling the higher methane concentrations we observed."
It sounds likely, but not certain, that more research will indicate that the methane leaked into the ground water as the natural gas was brought to the surface. If this proves true, it's good news because better well-casings are already being used and casings can presumably be made as good as they need to be. If this isn't true, if this gas is leaking upward through the bedrock because of the drilling activity, we need to know that as well. It may be that new techniques are needed. It may be that there are some areas where the local geology makes drilling or fracking unsafe.
Because there does need to be public confidence that vastly increased fracking is being done safely, it is a good thing that Energy Secretary Chu appointed a panel of qualified people "to identify, within 90 days of beginning their work, any immediate steps that can be taken to improve the safety and environmental performance of hydraulic fracturing. They will also develop, within six months of beginning their work, consensus recommended advice to the agencies on practices for shale extraction to ensure the protection of public health and the environment."
"America's vast natural gas resources can generate many new jobs and provide significant environmental benefits, but we need to ensure we harness these resources safely. I am looking forward to hearing from this diverse, respected group of experts on best practices for safe and responsible natural gas production."
We don't want a vast expansion of fracking, then some sort of scary incident that stops all fracking, then years of uncertainty and continued use of imported oil that could have been displaced by domestic natural gas. We do need to monitor the results of fracking and develop best practices. There are risks associated with any form of energy production or extraction; we need to know them, weigh them, and mitigate them where possible. We can't bury our heads in the shale.