A multi-isotope approach to determine the origin of methane and higher alkanes in groundwater of the St. Lawrence Platform, Saint-Édouard area, eastern Canada

Bordeleau, Geneviève; Rivard, Christine; Lavoie, Denis; Lefebvre, René; Ahad, Jason M. E.; Xu, Xiaomei; Mort, Andy

doi:10.1306/eg.04121817020

Cited by 10 publications

(14 citation statements)

References 63 publications

(87 reference statements)

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“…Considering the CH4- 2 H values in our samples, and based on published isotopic fractionation factors for methane oxidation, this process does not appear to be significant in the Saint-Édouard area, except for Ca-HCO3 type samples with very low methane concentrations and relatively high CH4-δ 13 C values (pink diamonds on Figure 8-A). Moreover, comparison of CH4- H and H2O- 2 H values confirmed that methane isotopic values in most samples are consistent with regular (non-oxidized) microbial methane formed via the CO2 reduction pathway using the local groundwater (Bordeleau et al, 2018b).…”

Section: Resultssupporting

confidence: 63%

“… 13 C values resembling thermogenic gas, and higher than expected DIC- 13 C values. An in-depth interpretation of these geochemical parameters (Bordeleau et al, 2018b) revealed that many samples contained late-stage microbial gas (Figure 8-C). Noteworthy, several of these samples also contain some thermogenic gas (Figure 8-B, C).…”

Section: Resultsmentioning

confidence: 99%

“…Finally, stable isotopic composition of ethane and propane, when available, did not provide additional information on the possibility of upward migration, as the values measured in groundwater, shallow bedrock gas and deep formation gas (Lorraine and Utica shales) span similar ranges (Bordeleau et al, 2018b).…”

Section: Resultsmentioning

confidence: 99%

“…Residential wells were also sampled at a low yield from an outdoor tap, prior to any treatment. Samples for alkane concentrations and isotopic composition were collected under a head of water (method described in Bordeleau et al, 2018aBordeleau et al, , 2018bBordeleau et al, & 2018c, which minimizes degassing but does not prevent it completely when methane is effervescent (Molofsky et al, 2016 Cl. Some of these analyses are quite atypical for this type of project (e.g., 36 Cl, CH4-14 C) and they provided important information on groundwater age and hydrocarbon source.…”

Section: Fieldwork and Analysesmentioning

confidence: 99%

“…Analytical methods used in the different laboratories are described in details in Bordeleau et al (2018aBordeleau et al ( , 2018bBordeleau et al ( & 2018c.…”

Section: Fieldwork and Analysesmentioning

confidence: 99%

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Assessing potential impacts of shale gas development on shallow aquifers through upward fluid migration: A multi-disciplinary approach applied to the Utica Shale in eastern Canada

Rivard

Bordeleau

Lavoie

et al. 2019

Marine and Petroleum Geology

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Potential impacts of shale gas development on shallow aquifers has raised concerns, especially regarding groundwater contamination. The intermediate zone separating shallow aquifers from shale gas reservoirs plays a critical role in aquifer vulnerability to fluid upflow, but the assessment of such vulnerability is challenging due to the general paucity of data in this intermediate zone. The ultimate goal of the project reported here was to develop a holistic multi-geoscience methodology to assess potential impacts of unconventional hydrocarbon development on freshwater aquifers related to upward migration through natural pathways. The study area is located in the St. Lawrence Lowlands (southern Quebec, Canada), where limited oil and gas exploration and no shale gas production have taken place. A large set of data was collected over a ~500 km 2 area near a horizontal shale gas exploration well completed and fracked into the Utica Shale at a depth of 2 km. To investigate the intermediate zone integrity, this project integrated research results from multiple sources in order to obtain a better understanding of the system hydrodynamics, including geology, hydrogeology, deep and shallow geophysics, soil, rock and groundwater geochemistry, and geomechanics. The combined interpretation of the multidisciplinary dataset demonstrates that there is no evidence of, and a very limited potential for, upward fluid migration from the Utica Shale reservoir to the shallow aquifer. Microbial and thermogenic methane in groundwater of this region appear to come from the shallow, organic-rich, fractured sedimentary rocks making up the regional aquifer. Nonetheless, diluted brines present in a few shallow wells close to and downstream of a normal fault revealed that some upward groundwater migration occurs, but only over a few hundred meters from the surface based on the isotopic signature of methane. The 3 methodology developed should help support regulations related to shale gas development aiming to protect groundwater.

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Section: Resultssupporting

confidence: 63%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Fieldwork and Analysesmentioning

confidence: 99%

“…Analytical methods used in the different laboratories are described in details in Bordeleau et al (2018aBordeleau et al ( , 2018bBordeleau et al ( & 2018c.…”

Section: Fieldwork and Analysesmentioning

confidence: 99%

See 3 more Smart Citations

Assessing potential impacts of shale gas development on shallow aquifers through upward fluid migration: A multi-disciplinary approach applied to the Utica Shale in eastern Canada

Rivard

Bordeleau

Lavoie

et al. 2019

Marine and Petroleum Geology

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Fault and natural fracture control on upward fluid migration: insights from a shale gas play in the St. Lawrence Platform, Canada

et al. 2018

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11Environmental concerns have been raised with respect to shale gas exploration and production, 12 especially in eastern Canada and northeastern United States. One of the major public concerns 13 has been the contamination of fresh water resources. This paper focuses on the investigation of 14 possible fluid upward migration through structural features in the intermediate zone (IZ), located 15 between a deep shale gas reservoir and shallow aquifers. The approach provides insights into how 16 such an investigation can be done when few data are available at depth. The study area is located 17 in the shale dominated succession of the St. Lawrence Platform (eastern Canada), where the Uti-18 ca Shale was explored for natural gas between 2006 and 2010. Detailed analyses were carried out 19 on both shallow and deep geophysical log datasets providing the structural attributes and prelimi-20 nary estimates of the hydraulic properties of faults and fractures. Results show that the active 21 255 words 29

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Continual long-term monitoring of methane in wells above the Utica Shale using total dissolved gas pressure probes

et al. 2022

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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 situ monitoring. 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 for methane concentrations. All three wells had high PTDG (reaching 53.0 m 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 to 4 m H2O), 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.

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A multi-isotope approach to determine the origin of methane and higher alkanes in groundwater of the St. Lawrence Platform, Saint-Édouard area, eastern Canada

Cited by 10 publications

References 63 publications

Assessing potential impacts of shale gas development on shallow aquifers through upward fluid migration: A multi-disciplinary approach applied to the Utica Shale in eastern Canada

Assessing potential impacts of shale gas development on shallow aquifers through upward fluid migration: A multi-disciplinary approach applied to the Utica Shale in eastern Canada

Fault and natural fracture control on upward fluid migration: insights from a shale gas play in the St. Lawrence Platform, Canada

Continual long-term monitoring of methane in wells above the Utica Shale using total dissolved gas pressure probes

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