OVERVIEW OF THE POTENTIAL RISKS OF SHALE GAS DEVELOPMENT AND HYDROFRACTURING ON WATER RESOURCES IN THE UNITED STATES

Advances in drilling technologies and production strategies such as horizontal drilling and hydraulic fracturing have significantly improved the production of natural gas by stimulating fluid flow from wells. Since 2008, these technological developments have spurred exponential growth of gas well drilling across the U.S. While the new drilling for shale gas and fracturing technologies could dramatically change the energy landscape in the U.S., recent scientific findings in Duke University [1, 2] show potential risks for water resources associated with shale gas development. High methane with a thermogenic carbon isotope fingerprint was found in domestic wells located less than a kilometer from shale gas wells in northeastern Pennsylvania [1]. One of the critical questions concerning the risk of contamination is the hydraulic connectivity between the deep shale gas formations and the shallow drinking water aquifers. Geochemical and isotopic compositions of shallow saline groundwater from northeastern Pennsylvania indicate mixing with the Marcellus brine, and thus possible natural pathways and hydraulic connection between deep underlying formations and shallow drinking water aquifers. The saline water was found to be unrelated to the current shale gas exploration in the area [2]. Other key environmental issue related to shale gas drilling is the disposal of the produced water, which is often highly saline, toxic, and radioactive. The direct and long-term impact of brine disposal on the quality and radioactivity of waterways in Pennsylvania is discussed.

[1] Osborn, S., Vengosh, A. Warner, N. Jackson, R. (2011). Methane contamination of drinking water accompanying gas drilling and hydro-fracking. Proceedings of the National Academy of Sciences of United States of America, 108, 8172-8176.

[2] Warner, N.R., Jackson, R.B., Darrah, T.H., Osborn, S., Down, A., Zhao, K., White, A., Vengosh, A. (2012) Geochemical evidence for possible natural migration of Marcellus Formation brine to shallow aquifers in Pennsylvania. Proceedings of the National Academy of Sciences of United States of America, July 9, 2012. 10.1073/pnas.1121181109.