CONFLICT OF INTEREST AND OTHER RELEVANT INFORMATION:

Chesapeake Energy Corporation funded consultants and the authors of this paper through their organizations of employment and, in the case of Donald Siegel, privately to do basic research on this temporal data set and prepare the paper. The authors of this report did all analysis and writing. The opinions and conclusions expressed in this paper are those of the authors and do not necessarily reflect those of Chesapeake Energy Corporation.

During the preparation of this paper, all authors worked for the organizations noted in authorship. Bert Smith is a former employee of Chesapeake Energy Corporation, having worked there from May 2012 to September 2013, and has been employed by Enviro Clean Cardinal since November 2013. While employed at Chesapeake Energy Corporation, he managed this temporal study, which was completed shortly after he left Chesapeake Energy Corporation. Enviro Clean Cardinal also does consulting work for Chesapeake Energy Corporation. Prior to May 2012, Bert Smith worked for Science Applications International Corporation, which consulted for Chesapeake Energy Corporation. Mark Becker has worked for Chesapeake Energy Corporation since March 2012; prior to that, he worked for the US Geological Survey for 24 yr. Donald Siegel works for Syracuse University, but he was funded privately for this work.

Neither Bert Smith nor Donald Siegel have competing corporate financial interests exceeding guidelines presented by AAPG Environmental Geosciences. Mark Becker is a current employee of Chesapeake Energy Corporation and owns stock in the company in an amount in excess of $5000.

Bert Smith is the lead author and contributed to the paper preparation, technical interpretations, and review of these data and paper. Mark Becker contributed to the paper preparation, technical interpretations, and review of these data and paper. Donald Siegel contributed to the paper preparation, technical interpretations, and review of these data and paper.

ABSTRACT

We herein document temporal changes in dissolved and gaseous methane concentrations in 12 domestic water wells completed in Late Devonian clastic aquifers in northeastern Pennsylvania over time periods from 0.2 to 2 yr. Wells with initial methane concentrations regarded as low (<5 mg/L), moderate (5–15 mg/L), and high (>15 mg/L) were all used in our study for comparative purposes.

The temporal variability of dissolved methane concentrations in groundwater from water wells ranged from tens to hundreds of percentage points in all categories of methane concentration, from low to high. Dissolved methane concentrations from most water wells with initial dissolved methane greater than 6 mg/L correlated (p ≤ 0.05) to natural changes in regional groundwater levels. Dissolved methane concentrations in groundwater are highest when regional groundwater levels are at seasonal lows, and they vary in response to groundwater fluctuation.

Water-level drawdown during water well pumping lowers methane solubility and induces it to exsolve from the groundwater into the well headspace. We observed that methane exsolution occurred when concentrations in groundwater exceeded 6 mg/L. In some cases with large drawdown or sustained water use, methane headspace in water wells can rapidly increase, reach ignitable concentrations, and remain elevated for days later.

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