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Mobility and persistence of methane in groundwater in a controlled-release field experiment

Nature Geoscience volume 10, pages 289294 (2017) | Download Citation

Abstract

Expansion of shale gas extraction has fuelled global concern about the potential impact of fugitive methane on groundwater and climate. Although methane leakage from wells is well documented, the consequences on groundwater remain sparsely studied and are thought by some to be minor. Here we present the results of a 72-day methane gas injection experiment into a shallow, flat-lying sand aquifer. In our experiment, although a significant fraction of methane vented to the atmosphere, an equal portion remained in the groundwater. We find that methane migration in the aquifer was governed by subtle grain-scale bedding that impeded buoyant free-phase gas flow and led to episodic releases of free-phase gas. The result was lateral migration of gas beyond that expected by groundwater advection alone. Methane persisted in the groundwater zone despite active growth of methanotrophic bacteria, although much of the methane that vented into the vadose zone was oxidized. Our findings demonstrate that even small-volume releases of methane gas can cause extensive and persistent free phase and solute plumes emanating from leaks that are detectable only by contaminant hydrogeology monitoring at high resolution.

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Acknowledgements

We acknowledge funding from the Natural Sciences and Engineering Research Council of Canada (NSERC), Strategic Project Grant no. 463045-14. Additional support was provided by the AITF/Eyes High Postdoctoral Fellowship programme (S.E.R.), the Campus Alberta Innovation Chair Program (M.S.), the Canadian Foundation for Innovation (M.S.), the Alberta Small Equipment Grant Program (M.S.), NSERC Discovery Grant (M.S.) and a Banting Postdoctoral Fellowship (C.M.S.). Special thanks for field assistance are given to A. Haggman, B. Ladd, D. Klazinga, T. Cheung, A. Verdin, R. Ingleton and P. Johnson.

Author information

Affiliations

  1. G360 Institute for Groundwater Research, University of Guelph, Ontario N1G 2W1, Canada

    • Aaron G. Cahill
    • , Colby M. Steelman
    • , John A. Cherry
    •  & Beth L. Parker
  2. Department of Earth, Ocean and Atmospheric Science, University of British Columbia, British Columbia V6T 1Z4, Canada

    • Aaron G. Cahill
    • , Olenka Forde
    •  & K. Ulrich Mayer
  3. Department of Geoscience, University of Calgary, Calgary, Alberta T2N 1N4, Canada

    • Olukayode Kuloyo
    • , S. Emil Ruff
    • , Bernhard Mayer
    • , Marc Strous
    •  & M. Cathryn Ryan

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Contributions

A.G.C., B.L.P. and J.A.C. conceived, designed, installed and oversaw the experiment. A.G.C., C.M.S., O.F., O.K. and S.E.R. collected and processed all field data. All authors interpreted the multi-disciplinary data sets. A.G.C., B.L.P., J.A.C. and C.M.S. generated the first draft of the manuscript before all authors contributed to refinement and finalization.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Beth L. Parker.

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DOI

https://doi.org/10.1038/ngeo2919

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