| Title | Continual long-term monitoring of methane in wells above the Utica Shale using total dissolved gas pressure probes |
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| Author | Roy, J; Bordeleau, G; Rivard, C ; Ryan, C; Malet, X; Brown, S; Tremblay, V |
| Source | Hydrogeology Journal 2022 p. 1-15, https://doi.org/10.1007/s10040-022-02452-1  Open Access |
| Image |  |
| Year | 2022 |
| Alt Series | Natural Resources Canada, Contribution Series 20210177 |
| Publisher | Springer |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | Quebec |
| NTS | 31H/03 |
| Lat/Long WENS | -73.5000 -73.0000 45.2500 45.0000 |
| Subjects | hydrogeology; groundwater; gas; equipment standards; field work; field methods |
| Illustrations | location maps; tables; schematic representations; graphs; time series; stacked profiles; plots |
| Program | Environmental
Geoscience Program Management |
| Released | 2022 02 21 |
| Abstract | 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 (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 ID | 328620 |
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