Browsing by Author "Humez, P."

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    An 8-year record of gas geochemistry and isotopic composition of methane during baseline sampling at a groundwater observation well in Alberta (Canada)
    (Springer, 2016-02-01) Humez, P.; Mayer, B.; Nightingale, M.; Ing, J.; Becker, V.; Jones, D.; Lam, V.
    Variability in baseline groundwater methane concentrations and isotopic compositions was assessed while comparing free and dissolved gas sampling approaches for a groundwater monitoring well in Alberta (Canada) over an 8-year period. Methane concentrations in dissolved gas samples (n = 12) were on average 4,380 ± 2,452 μg/L, yielding a coefficient of variation (CV) >50 %. Methane concentrations in free gas samples (n = 12) were on average 228,756 ± 62,498 ppm by volume, yielding a CV of 27 %. Quantification of combined sampling, sample handling and analytical uncertainties was assessed via triplicate sampling (CV of 19 % and 12 % for free gas and dissolved gas methane concentrations, respectively). Free and dissolved gas samples yielded comparable methane concentration patterns and there was evidence that sampling operations and pumping rates had a marked influence on the obtained methane concentrations in free gas. δ13CCH4 and δ2HCH4 values of methane were essentially constant (−78.6 ± 1.3 and −300 ± 3 ‰, respectively) throughout the observation period, suggesting that methane was derived from the same biogenic source irrespective of methane concentration variations. The isotopic composition of methane constitutes a robust and highly valuable baseline parameter and increasing δ13CCH4 and δ2HCH4 values during repeat sampling may indicate influx of thermogenic methane. Careful sampling and analytical procedures with identical and repeatable approaches are required in baseline-monitoring programs to generate methane concentration and isotope data for groundwater that can be reliably compared to repeat measurements once potential impact from oil and gas development, for example, may occur.
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    Recommendations for integrating isotope fingerprinting in Environmental Baseline Assessment as part of regulation on unconventional gas exploration and exploitation
    (2019-01) Kloppmann, W.; Mayer, Bernhard; Humez, P.; Osselin, F.; Gaucher, E.
    Multi-isotope fingerprinting of gases (methane, higher alkanes, CO 2) and of dissolved compounds in saline fluids (C, S, O, Sr, B, Li, U, Cu, Zn,…) allows for the discrimination of point contamination related to unconventional gas development compared to the environmental baseline. We present results from a multitude of settings worldwide with a focus on the identification of thermogenic stray gases from the natural background values, taking into account the prevailing redox conditions. A second aspect are the specific isotope fingerprints of flowback waters from hydraulic fracturing compared to natural saline fluids.