Dataset Information

Fate and Transport of Shale-derived, Biogenic Methane.

ABSTRACT: Natural gas extraction from unconventional shale gas reservoirs is the subject of considerable public debate, with a key concern being the impact of leaking fugitive natural gases on shallow potable groundwater resources. Baseline data regarding the distribution, fate, and transport of these gases and their isotopes through natural formations prior to development are lacking. Here, we define the migration and fate of CH₄ and ?¹³C-CH₄ from an early-generation bacterial gas play in the Cretaceous of the Williston Basin, Canada to the water table. Our results show the CH₄ is generated at depth and diffuses as a conservative species through the overlying shale. We also show that the diffusive fractionation of ?¹³C-CH₄ (following glaciation) can complicate fugitive gas interpretations. The sensitivity of the ?¹³C-CH₄ profile to glacial timing suggests it may be a valuable tracer for characterizing the timing of geologic changes that control transport of CH₄ (and other solutes) and distinguishing between CH₄ that rapidly migrates upward through a well annulus or other conduit and CH₄ that diffuses upwards naturally. Results of this study were used to provide recommendations for designing baseline investigations.

SUBMITTER: Hendry MJ

PROVIDER: S-EPMC5501783 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature

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Fate and Transport of Shale-derived, Biogenic Methane.

Hendry M Jim MJ Schmeling Erin E EE Barbour S Lee SL Huang M M Mundle Scott O C SOC

Scientific reports 20170707 1

Natural gas extraction from unconventional shale gas reservoirs is the subject of considerable public debate, with a key concern being the impact of leaking fugitive natural gases on shallow potable groundwater resources. Baseline data regarding the distribution, fate, and transport of these gases and their isotopes through natural formations prior to development are lacking. Here, we define the migration and fate of CH4 and δ13C-CH4 from an early-generation bact ...[more]

PMID: 28687757

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Project description:Biogenic sulfide production is a common problem in the oil industry, and can lead to costly hydrocarbon processing and corrosion of extraction infrastructure. The same phenomenon has recently been identified in shale gas extraction by hydraulic fracturing, and organic additives in fracturing fluid have been hypothesized to stimulate this process. Constraining the relative effects of the numerous organic additives on microbial metabolism in situ is, however, extremely challenging. Using a bespoke bioreactor system we sought to assess the potential for guar gum, the most commonly used gelling agent in fracturing fluids, to stimulate biogenic sulfide production by sulfate-reducing microorganisms at elevated pressure. Two pressurized bioreactors were fed with either sulfate-amended freshwater medium, or low-sulfate natural surface water, in addition to guar gum (0.05 w/v%) and an inoculum of sulfate-reducing bacteria for a period of 77 days. Sulfide production was observed in both bioreactors, even when the sulfate concentration was low. Analysis of 16S rRNA gene sequences indicate that heterotrophic bacteria closely associated with the genera Brevundimonas and Acinetobacter became enriched early in the bioreactor experiments, followed by an increase in relative abundance of 16S rRNA genes associated with sulfate-reducing bacteria (Desulfosporosinus and Desulfobacteraceae) at later time points. Results demonstrate that guar gum can stimulate acid- and sulfide-producing microorganisms at elevated pressure, and may have implications for the potential role in microbially induced corrosion during hydraulic fracturing operations. Key differences between experimental and in situ conditions are discussed, as well as additional sources of carbon and energy for biogenic sulfide production during shale gas extraction. Our laboratory approach can be tailored to better simulate deep subsurface conditions in order to probe the role of other fracturing fluid additives and downhole parameters on microbial metabolisms observed in these systems. Such baseline studies will prove essential for effective future development of shale gas worldwide.

Dataset Information

Fate and Transport of Shale-derived, Biogenic Methane.

Publications

Fate and Transport of Shale-derived, Biogenic Methane.

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