Origin, distribution and hydrogeochemical controls on methane occurrences in shallow aquifers, southwestern Ontario, Canada

McIntosh, Jennifer C.; Grasby, Stephen E.; Hamilton, Stewart M.; Osborn, Stephen G.

doi:10.1016/j.apgeochem.2014.08.001

Cited by 64 publications

(42 citation statements)

References 47 publications

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“…The lack of significant methane in the Ordovician shales may be due to a combination of a greater abundance of competing electron acceptors (e.g. SO 4 , Fe) and lower quantities and/ or less labile organic matter (McIntosh et al 2014). The evidence of ongoing geochemical processes related to biogenic gas production in the shales, and the general similarity between the concentrations of gas in older and younger waters with increasing depth, further supports the theory (e.g.…”

Section: Groundwater Geochemistrysupporting

confidence: 58%

“…CH 4(aq) increases to almost saturation by 15 m depth and remains at a similarly high concentration with depth. There is also a close spatial correlation between elevated CH 4(aq) and the organic rich shales and overburden that overlies the shales (Hamilton 2011;McIntosh et al 2014). The very high concentration of the final bin is due to bursts of free bubbles encountered during collection of several deep samples, resulting in higher dissolved methane concentrations.…”

Section: Groundwater Geochemistrymentioning

confidence: 89%

“…Hydrogen sulfide was determined in the field using the methylene-blue method with a HACH model 2238-01 test kit (0.01 ppm lower detection limit). Dissolved CH 4 and CO 2 were also measured and the methods, results and implications of the CH 4 distribution are discussed in detail in McIntosh et al (2014).…”

Section: Methodsmentioning

confidence: 99%

“…Bedrock wells and many deeper overburden wells in southwestern Ontario are most often completed in a hydraulically conductive zone near the interface between bedrock and glacial overburden (Weaver et al 1995) that is often referred to as the interface or 'contact' aquifer. Groundwaters hosted in the contact aquifer generally exhibit the chemical character of bedrock and the bedrock-derived basal till (Singer et al 2003) in both dissolved solid (Hamilton 2015) and dissolved gas (McIntosh et al 2014) content.…”

Section: Surficial Geologymentioning

confidence: 99%

“…These strata include five gas-yielding shale units (Armstrong and Carter 2010), treated here in four groups: (1) the Devonian Kettle Point Formation, (2) Hamilton Group, (3) Marcellus Formation, and (4) the Ordovician Queenston and underlying Georgian Bay-Blue Mountain formations. The Devonian shales are treated in greater detail in this report because of their spatial association with significant methane accumulations (Hamilton 2015;McIntosh et al 2014) and with decadal changes in regional water levels. Another paper related to this work (McIntosh et al 2014) discusses the spatial distribution of gas, isotopic and chemical composition of the gas, and mechanisms and timing of gas formation in Paleozoic bedrock and overburden deposits, and its relationship to water chemistry.…”

Section: Introductionmentioning

confidence: 99%

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The effect of long-term regional pumping on hydrochemistry and dissolved gas content in an undeveloped shale-gas-bearing aquifer in southwestern Ontario, Canada

et al. 2015

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Baseline groundwater geochemical mapping of inorganic and isotopic parameters across 44,000 km 2 of southwestern Ontario (Canada) has delineated a discreet zone of natural gas in the bedrock aquifer coincident with an 8,000-km 2 exposure of Middle Devonian shale. This study describes the ambient geochemical conditions in these shales in the context of other strata, including Ordovician shales, and discusses shale-related natural and anthropogenic processes contributing to hydrogeochemical conditions in the aquifer. The three Devonian shales-the Kettle Point Formation (Antrim equivalent), Hamilton Group and Marcellus Formation-have higher DOC, DIC, HCO 3 , CO 2(aq) , pH and iodide, and much higher CH 4(aq). The two Ordovician shales-the Queenston and Georgian-Bay/Blue Mountain Formations-are higher in Ca, Mg, SO 4 and H 2 S. In the Devonian shale region, isotopic zones of Pleistoceneaged groundwater have halved in size since first identified in the 1980s; potentiometric data implicate regional groundwater extraction in the shrinkage. Isotopically younger waters invading the aquifer show rapid increases in CH 4(aq) , pH and iodide with depth and rapid decrease in oxidized carbon species including CO 2 , HCO 3 and DIC, suggesting contemporary methanogenesis. Pumping in the Devonian shale contact aquifer may stimulate methanogenesis by lowering TDS, removing products and replacing reactants, including bicarbonate, derived from overlying glacial sedimentary aquifers.

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Section: Groundwater Geochemistrysupporting

confidence: 58%

Section: Groundwater Geochemistrymentioning

confidence: 89%

Section: Methodsmentioning

confidence: 99%

Section: Surficial Geologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The effect of long-term regional pumping on hydrochemistry and dissolved gas content in an undeveloped shale-gas-bearing aquifer in southwestern Ontario, Canada

et al. 2015

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Fate and transport of dissolved methane and ethane in cretaceous shales of the Williston Basin, Canada

Hendry

Barbour

Schmeling

et al. 2016

Water Resources Research

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Baseline characteristics of dissolved methane (CH4) and ethane (C2H6) and their stable isotopes in thick, low hydraulic conductivity, Cretaceous shales were determined using high‐resolution core profiling at four sites in the Williston Basin (WB), Canada. Positive correlations with the conservative natural tracer Cl− reflected a lack of measureable production or consumption of gases in the shale to the depth investigated (150 m below ground, BG) and suggest CH4 and C2H6 concentrations near the interface with overlying Quaternary sediments are controlled by lateral migration and dilution in permeable zones. Curvilinear increasing concentrations with depth in the shale at all sites coupled with 1‐D solute transport modeling suggest long‐term (over millions of years) upward diffusion of CH4 and C2H6 from deeper WB sources, likely the Second White Speckled Shale Formation (SWSS; ∼790 m BG). δ13C‐CH4 profiles in the shale are consistent with upward diffusional fractionation of isotopes from the SWSS. Distinct CH4 and C2H6 isotope values of gases in the shales versus 13C‐enriched thermogenic isotopic signatures of CH4 and C2H6 in deeper oil‐producing WB intervals could be used to identify fugitive gases originating deeper in the Basin.

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Methane in Groundwater: Pathways

Martini

Osborn

McIntosh

2019

Encyclopedia of Water

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Groundwater can contain measurable quantities of methane associated with in situ processes of methanogenesis and desorption from geologic materials, and also from external migration from deeper gas‐bearing units. It may also contain “fugitive gas” due to leakage from exploration and production of hydrocarbons or from the microbial breakdown of organic contaminants introduced to the aquifer. More recently, natural gas production via high volume hydraulic fracturing of tight formations has been implicated as a route for both methane and other fluids to enter groundwater resources. While distinguishing the source of the gas is often critical, secondary processes such as mixing and aerobic and anaerobic oxidation make these identifications difficult. Important to these determinations is an understanding of the hydrology, geology, and history of development in the watershed, coupled with detailed geochemical and isotopic analysis.

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Origin, distribution and hydrogeochemical controls on methane occurrences in shallow aquifers, southwestern Ontario, Canada

Cited by 64 publications

References 47 publications

The effect of long-term regional pumping on hydrochemistry and dissolved gas content in an undeveloped shale-gas-bearing aquifer in southwestern Ontario, Canada

The effect of long-term regional pumping on hydrochemistry and dissolved gas content in an undeveloped shale-gas-bearing aquifer in southwestern Ontario, Canada

Fate and transport of dissolved methane and ethane in cretaceous shales of the Williston Basin, Canada

Methane in Groundwater: Pathways

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