Friday, May 13, 2011

Hydraulic fracturing science: what the latest study does (and doesn't) appear to tell us

For those who did not see the article link on the Environmental Law Professors listserv, four Duke scientists have published a study in the Proceedings of the National Academy of Sciences that addresses possible connections between natural gas extraction (through drilling and hydraulic fracturing) and methane contamination of shallow groundwater in the Appalachian region.  The study concludes that groundwater in areas with gas extraction activity has higher concentrations of thermogenic methane--methane from deep formations--than does the groundwater in areas without extraction activity.  On average, the methane concentration in water wells sampled in the active extraction areas was seventeen times higher than the concentration in inactive areas.  Most importantly, the study finds that "gas-phase transport of methane upward to the shallow groundwater zones sampled" may be occurring, suggesting that drilling and/or fracturing--not just naturally-occcuring methane around the groundwater--could be contributing to the methane contamination.  The study cannot, however, pinpoint the exact causal mechanism for this apparent upward migration of methane.  The most likely source of the methane in groundwater, the authors conclude, is gas that is transported in gas phase from shale formations to  groundwater.  Alternatively, "gas-rich solutions" from deep formations could be physically displaced in the extraction process and migrate upward to water, but the authors believe that this is unlikely.  Secondly, "leaky gas-well casings" may allow methane to escape and to travel laterally and/or vertically to groundwater.  Finally, hydraulic fracturing could expand fractures beyond the formation targeted by the fracturing.  Then, according to the study, "The reduced pressure following the fracturing activities could release methane in solution, leading to methane exsolving rapidly from solution, allowing methane gas to potentially migrate upward through the fracture system."  The study finds no evidence of brines or fracturing fluids contaminating groundwater.  It concludes--unsurprisingly--that "[m]ore research is needed." 

-Hannah Wiseman

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This study is interesting. The methane levels are up to 17 times higher, yet there is no contamination from fracturing fluids in the groundwater. This just reinforces how careful drilling companies need to be when they use fracking to produce oil or natural gas. I believe if Hydraulic Fracturing is done carefully and in full compliance with governmental regulations it can be safe, but studies like this highlight the need for close oversight. Americans nee to produce our own energy, and we also need to protect the environment. I have been reading studies on this website.

Posted by: kurt | Aug 8, 2012 9:51:28 AM

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