@article{8da379fe64624be88ca749fb049289c1,
title = "Detecting and explaining why aquifers occasionally become degraded near hydraulically fractured shale gas wells",
abstract = "Extensive development of shale gas has generated some concerns about environmental impacts such as the migration of natural gas into water resources. We studied high gas concentrations in waters at a site near Marcellus Shale gas wells to determine the geological explanations and geochemical implications. The local geology may explain why methane has discharged for 7 years into groundwater, a stream, and the atmosphere. Gas may migrate easily near the gas wells in this location where the Marcellus Shale dips significantly, is shallow (∼1 km), and is more fractured. Methane and ethane concentrations in local water wells increased after gas development compared with predrilling concentrations reported in the region. Noble gas and isotopic evidence are consistent with the upward migration of gas from the Marcellus Formation in a free-gas phase. This upflow results in microbially mediated oxidation near the surface. Iron concentrations also increased following the increase of natural gas concentrations in domestic water wells. After several months, both iron and SO4 2− concentrations dropped. These observations are attributed to iron and SO4 2− reduction associated with newly elevated concentrations of methane. These temporal trends, as well as data from other areas with reported leaks, document a way to distinguish newly migrated methane from preexisting sources of gas. This study thus documents both geologically risky areas and geochemical signatures of iron and SO4 2− that could distinguish newly leaked methane from older methane sources in aquifers.",
keywords = "Hydraulic fracturing, Methane, Noble gases, Shale gas, Water quality",
author = "Josh Woda and Tao Wen and David Oakley and David Yoxtheimer and Terry Engelder and {Clara Castro}, M. and Brantley, {Susan L.}",
note = "Funding Information: We thank B. Lindsey of the USGS, the PA DEP, Z. Li, and A. Herman for providing or helping with predrilling data; the homeowners who provided access to private land in the Sugar Run valley; T. Sowers for analytical assistance for hydrocarbons; H. Ramirez, K. Jahn, L. Mateo, and G. Mount for field help; and Midland Valley for providing Move software through their academic software initiative. C. M. Hall of the Noble Gas Laboratory at University of Michigan codeveloped the sampling apparatus for noble gases described in SI Appendix. This work was funded by National Science Foundation IIS Award 1639150 (to S.L.B.) (Pennsylvania State University) and by a gift to Pennsylvania State University for the Pennsylvania State University General Electric Fund for the Center for Collaborative Research on Intelligent Natural Gas Supply Systems. Funding Information: ACKNOWLEDGMENTS. We thank B. Lindsey of the USGS, the PA DEP, Z. Li, and A. Herman for providing or helping with predrilling data; the homeowners who provided access to private land in the Sugar Run valley; T. Sowers for analytical assistance for hydrocarbons; H. Ramirez, K. Jahn, L. Mateo, and G. Mount for field help; and Midland Valley for providing Move software through their academic software initiative. C. M. Hall of the Noble Gas Laboratory at University of Michigan codeveloped the sampling apparatus for noble gases described in SI Appendix. This work was funded by National Science Foundation IIS Award 1639150 (to S.L.B.) (Pennsylvania State University) and by a gift to Pennsylvania State University for the Pennsylvania State University General Electric Fund for the Center for Collaborative Research on Intelligent Natural Gas Supply Systems. Publisher Copyright: {\textcopyright} 2018 National Academy of Sciences. All Rights Reserved.",
year = "2018",
month = dec,
day = "4",
doi = "10.1073/pnas.1809013115",
language = "English (US)",
volume = "115",
pages = "12349--12358",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
issn = "0027-8424",
publisher = "National Academy of Sciences",
number = "49",
}