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TitleContinual long-term monitoring of methane in wells above the Utica Shale using total dissolved gas pressure probes
 
AuthorRoy, J; Bordeleau, G; Rivard, CORCID logo; Ryan, C; Malet, X; Brown, S; Tremblay, V
SourceHydrogeology Journal 2022 p. 1-15, https://doi.org/10.1007/s10040-022-02452-1 Open Access logo Open Access
Image
Year2022
Alt SeriesNatural Resources Canada, Contribution Series 20210177
PublisherSpringer
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceQuebec
NTS31H/03
Lat/Long WENS -73.5000 -73.0000 45.2500 45.0000
Subjectshydrogeology; groundwater; gas; equipment standards; field work; field methods
Illustrationslocation maps; tables; schematic representations; graphs; time series; stacked profiles; plots
ProgramEnvironmental Geoscience Program Management
Released2022 02 21
AbstractMonitoring of dissolved methane concentrations in groundwater is required to identify impacts from oil and gas development and to understand temporal variability under background conditions. Currently, long-term (i.e., multiyear) monitoring is performed via periodic groundwater sampling; hence, the data are temporally limited and can suffer from degassing losses in-well and at surface for groundwater with high dissolved gas concentrations. The application of total dissolved gas pressure (PTDG) probes for long-term monitoring of methane-rich groundwater was investigated for >2 years in three monitoring wells in a low-permeability bedrock aquifer above the Utica Shale, Canada. The advantage of these probes is that they allow for continual in situmonitoring. A hydraulic packer was installed in each well, below which PTDG and water pressure were measured every 15 or 30 min. The major dissolved gas species composition, required to calculate methane concentrations from PTDG, was determined from groundwater samples collected approximately bimonthly.Methane was the dominant gas in each well (~80-97%), with relatively consistent composition over time, indicating PTDG provided a reasonable proxy formethane concentrations. All three wells had high PTDG (reaching 53.0m H2O), with PTDG-derived methane concentrations (34-156 mg/L) much higher (3-12 times) and relatively more stable than determined by conventional groundwater analysis. PTDG monitoring also revealed substantial short-term changes during pumping and between sampling events (up to4mH2O), possibly associated with background variability. Limitations and technical remedies are discussed. This study demonstrates that PTDG probes can be a valuable tool for monitoring methane-rich groundwater.
Summary(Plain Language Summary, not published)
Monitoring of dissolved methane concentrations in groundwater is required to identify impacts from oil and gas development and to understand temporal variability under background conditions. Currently, long-term monitoring is performed via periodic groundwater (GW) sampling; hence, the data are temporally limited and can suffer from degassing losses for GW with high dissolved gas concentrations. In this study, the application of total dissolved gas pressure (PTDG) probes for long-term monitoring of methane-rich GW was investigated for >2 years in three monitoring wells in a low-permeability bedrock aquifer above the Utica Shale. The great advantage of these probes is that they allow for continual in situ monitoring. The dissolved gas composition, required to calculate methane concentrations from PTDG, was determined from GW samples collected bimonthly. This study demonstrates that PTDG-probes can be a valuable, even critical tool for monitoring methane-rich GW.
GEOSCAN ID328620

 
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