Using permutational and multivariate statistics to understand inorganic well water chemistry and the occurrence of methane in groundwater, southeastern New Brunswick, Canada

Loomer, Diana B.; MacQuarrie, Kerry T.B.; Al, Tom A.

doi:10.1016/j.scitotenv.2019.04.256

Cited by 9 publications

(6 citation statements)

References 40 publications

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“…Therefore, the presence of thermogenic C 1 in the shallow groundwater is thought to be natural. Elevated C 1 concentrations have also been observed in other Cumberland Group wells located along the southeastern margin of the Moncton subbasin (Loomer et al 2019). In that area, the Cumberland Group forms a thin cover directly over the Horton Group and hydrocarbon gases may be migrating upward into the overlying Cumberland Group.…”

Section: Hydrocarbon Gases In Shallow Groundwatermentioning

confidence: 83%

“…Groundwater data are reported for a subset of 52 wells from the two regional studies Copyright © Atlantic Geology 2020 comparison of isotopic compositions of hydrocarbon gas in shallow groundwater and a deep oil and natural gas reservoir in southeastern new brunswick, canada Loomer et al 2019). The dataset represents groundwater with dissolved C 1 concentrations >0.1 mg/L and includes wells located within all five study areas.…”

Section: Sampling and Analysesmentioning

confidence: 99%

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Comparison of isotopic compositions of hydrocarbon gas in shallow groundwater and a deep oil and natural gas reservoir in southeastern New Brunswick, Canada

Loomer

MacQuarrie

2020

atgeol

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Isotopic analyses of natural gas from the Stoney Creek oil field in New Brunswick indicate carbon (δ13C) and hydrogen (δ2H) values in methane (C1) of -42.4 ± 0.7‰ VPDB and -220.9 ± 3.2‰ VSMOW, respectively. Isotopic data and a gas molecular ratio of 12 ± 1 indicate a wet thermogenic gas formed with oil near the onset of the oil-gas transition zone. The isotopic profiles of the C1–C5 hydrocarbon gases are consistent with kinetic isotope effect models. The Albert Formation of the Horton Group hosts the Stoney Creek oil field (SCOF) and the McCully gas field (MCGF) the only other gas-producing field in the province. Both are thermogenic in origin; however, the SCOF gas has a lower thermal maturity than the MCGS. Hydrocarbon gas composition in shallow aquifers across southeastern New Brunswick was also evaluated. Gas source interpretations based on δ13C and δ2H values are uncertain; oxidation and biogenic overprinting are common and complicate interpretation. The effect of oxidation on δ13C and δ2H values was apparent when C1 concentrations were ≤1 mg/L. In some samples with C1 concentrations >5 mg/L, isotopic discrimination methods point to a biogenic origin. However, the molecular ratios <75 and the presence of >C3 fractions, indicate a thermogenic origin. This suggests a thermogenic isotopic signature has been overprinted by biological activity.

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Section: Hydrocarbon Gases In Shallow Groundwatermentioning

confidence: 83%

Section: Sampling and Analysesmentioning

confidence: 99%

Comparison of isotopic compositions of hydrocarbon gas in shallow groundwater and a deep oil and natural gas reservoir in southeastern New Brunswick, Canada

Loomer

MacQuarrie

2020

atgeol

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“…Those solutions were then applied to the cells along the transport domain, creating a stepped profile between the source‐region brine and dilute, shallow groundwater. The shallow groundwater composition was based on a water sample collected from a well completed in Cumberland Group bedrock (sample SUS188 in Loomer et al., 2019). The P and T in the model cells were also varied along the length of the transport domains in 10 steps in accordance with the geothermal and hydrostatic gradients.…”

Section: Modeling Approachmentioning

confidence: 99%

Reactive Transport Modeling of Natural Gas Molecular and Isotopic Evolution During Diffusive Transport in the Subsurface

Loomer

MacQuarrie

2021

Water Resources Research

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Reactive transport modeling was employed to investigate the relative importance of fractionations associated with gas solubility, sorption and diffusive transport on dissolved methane, ethane and propane concentrations and the isotopic composition of carbon in methane (δ13C1) in groundwater. Temperature, pressure and salinity dependencies for the hydrocarbon gases were incorporated. Gas molecular ratios, C1/(C2 + C3), increased with diffusive transport, transitioning from thermogenic values to values typically indicative of biogenic gas sources, >1,000, at the leading edge of the diffusive front. Diffusive isotopic fractionation had a large effect on δ13C1 values, with fractionations ranging from −36‰ to −107‰, the difference being a function of the diffusive fractionation factor (αD0). Larger fractionations resulted from αD0 determined at relatively low pressures, 5–50 atm, and temperatures, 20°C–25°C. Less fractionation occurred with αD0 measured at higher pressures and temperature, 30–89 atm and 90°C. The extremely depleted δ13C1 values indicated from the modeling, less than −110‰, have not been observed in shallow groundwater, suggesting that diffusive fractionation of δ13C1 is offset by other processes such as microbial oxidation. 2k factorial analysis was used to assess the model sensitivity to specific parameters: estimations of hydrocarbon travel distance are most sensitive to porosity and tortuosity, while the molecular ratio was most sensitive to the free‐water diffusion coefficient, and the isotopic fractionation was most sensitive to αD0. The magnitude of diffusive fractionation on the molecular and isotopic composition of transported hydrocarbon gas may be similar to fractionations from microbial oxidation and mixing between different sources.

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“…Dissolved methane is often present in shallow groundwater (e.g., Barker and Fritz 1981;Darling and Gooddy 2006;Moritz et al 2015;Humez et al 2016a;Loomer et al 2019), and although it is not toxic, its release from groundwater through or around wells or directly to overlying soils presents an explosion hazard to well houses and underground structures (Engelder and Zevenbergen 2018). Within an aquifer, the oxidation of methane can lead to the mobilization of trace metals such as arsenic (Cahill et al 2017;Glodowska et al 2020), and taste-odour issues (Gorody 2012).…”

Section: Introductionmentioning

confidence: 99%

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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Using permutational and multivariate statistics to understand inorganic well water chemistry and the occurrence of methane in groundwater, southeastern New Brunswick, Canada

Cited by 9 publications

References 40 publications

Comparison of isotopic compositions of hydrocarbon gas in shallow groundwater and a deep oil and natural gas reservoir in southeastern New Brunswick, Canada

Comparison of isotopic compositions of hydrocarbon gas in shallow groundwater and a deep oil and natural gas reservoir in southeastern New Brunswick, Canada

Reactive Transport Modeling of Natural Gas Molecular and Isotopic Evolution During Diffusive Transport in the Subsurface

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

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