Alarming Differences in Dissolved Methane Across Commercial Laboratories Finding a Fix

Oral Presentation

Prepared by R. Vitale, D. Gratson, L. Work, S. Brower
Environmental Standards, Inc., 1140 Valley Forge Road, Valley Forge, Pennsylvania, 19482, United States


Contact Information: rvitale@envstd.com; 610-935-5577


ABSTRACT

Alarming Differences in Dissolved Methane across Commercial Laboratories Finding a Fix

Rock Vitale, David Gratson, Steve Brower, and Lydia Work (Environmental Standards, Inc., Valley Forge, PA USA); and the Marcellus Shale Coalition
(Pittsburgh, PA, USA)

The analysis of groundwater for dissolved light gases, including methane, is a required or recommended practice for establishing baseline and post well completion conditions in the vicinity of unconventional shale gas production. Historically, data collected by members of the Marcellus Shale Coalition (MSC) have been of concern due to disparate dissolved methane results in domestic groundwater wells and its member companies have identified large variations in the reported concentrations between laboratories from split samples. The MSC established a Workgroup that identified the need for round robin laboratory studies to fully understand the magnitude of the problem and to guide further work aimed at removing the dissolved gas concentration variances.

Approach. The MSC commissioned three round robin studies for the analysis of dissolved light gases. The first two studies were commissioned in 2014-2016 and entailed a total of eighteen commercial and one government laboratory. Each laboratory volunteered to analyzed blind samples. The first study employed groundwater that had been collected at two separate wells locations. In the second study four reference standards were submitted blind. Building on these earlier studies the MSC commissioned a third study that was completed in Spring 2018. Again reference standards were submitted, however the laboratories were informed of the concentration and requested to self-diagnose the source(s) of their bias.

Lessons Learned. The first two studies identified significant variation among the results, with dissolved methane values that varied from 7.4 to 34.6 mg/L for a single sample groundwater location well. The second study also again showed considerable variability, with a number of results 40-60% low relative to the prepared standards. Phase three provided a path forward for the laboratories to identify their specific source(s) of error and to correct their procedures. This presentation will outline the first two phases, discuss the third study in detail, and provide recommendations for achieving a process and analytical method to reduce the bias and variability for the analysis of dissolved methane and other light gases.