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TitleMicrobial and thermochemical controlled sulfur cycle in the Early Triassic sediments of the Western Canadian Sedimentary Basin
Associated Data
AuthorLiseroudi, M H; Ardakani, O HORCID logo; Pedersen, P K; Stern, R A; Wood, J M; Sanei, HORCID logo
SourceJournal of the Geological Society 2021 p. 1-20,
Alt SeriesNatural Resources Canada, Contribution Series 20200695
Mediapaper; on-line; digital
File formatpdf; html
ProvinceAlberta; British Columbia
NTS83L/13; 83L/14; 83L/15; 83M/02; 83M/03; 83M/04; 83M/05; 83M/06; 83M/07; 83M/10; 83M/11; 83M/12; 83M/13; 83M/14; 83M/15; 93P/01; 93P/02; 93P/06; 93P/07; 93P/08; 93P/09; 93P/10; 93P/11; 93P/14; 93P/15; 93P/16
AreaDawson Creek
Lat/Long WENS-121.5000 -118.5000 56.0000 54.7500
Subjectsfossil fuels; geochemistry; sedimentology; mineralogy; Nature and Environment; Science and Technology; Lower Triassic; paleoenvironment; continental margins; continental shelf; sulphur geochemistry; pyrite; hydrogen sulphide; sulphate; isotopic studies; sulphur; diagenesis; anhydrite; bitumen; microorganisms; biogeochemistry; petrographic analyses; mass spectrometer analysis; methane; thermal analyses; reservoir rocks; burial history; modelling; Western Canada Sedimentary Basin; Montney Formation; Phanerozoic; Mesozoic; Triassic
Illustrationslocation maps; geoscientific sketch maps; stratigraphic columns; schematic representations; models; tables; photomicrographs; geochronological charts; histograms; plots; time series
ProgramGeoscience for New Energy Supply (GNES) Shale Reservoir Characterization
Released2021 03 08
AbstractPyrite is one of three main sulfur reservoirs and one of the biggest fluxes in the global sulfur cycle. The sulfur isotopic signature of hydrogen sulfide, pyrite and their parent sulfate is widely used as a proxy for tracking sulfur cycle variations in diagenetic environments. The Early Triassic Montney Formation in the Western Canadian Sedimentary Basin is characterized by distinct regional variations in pyrite abundance, type, sulfur isotopic signature and H2S concentrations in natural gas. Two main types of framboidal and crystalline pyrite were identified to have formed during various stages of diagenesis. The wide range of delta-34Spyrite values (-34.4 to +57.8 per mille V-CDT) demonstrates that the sulfur cycle in the Montney Formation is governed by both microbial and thermochemical processes. The comparison of delta-34S of the produced-gas H2S with pyrite, anhydrite and solid bitumen of the Montney, and underlying and overlying formations, suggests a mixture of dominantly in situ and minor migrated H2S with thermochemical sulfate reduction origin in the Montney Formation. The large diagenetic variations in pyrite types and delta-34Spyrite values suggest a lack of direct biogeochemical connection to the sulfur cycle and emphasize the importance of careful petrographic observations and micro-scale isotopic analysis of sedimentary units to accurately reconstruct paleoenvironmental conditions.
Summary(Plain Language Summary, not published)
The Early Triassic Montney Formation in the Western Canadian Sedimentary Basin (WCSB), one of the major unconventional resources in Canada, is characterized by distinct regional variation in H2S concentrations within natural gas-producing wells, pyrite abundance, and type, as well as sulfur isotopic signature. The current study aims to unravel the diagenetic sulfur cycle in this unconventional gas play using H2S/HS (?H2S) and pyrite sulfur isotopic composition to better understand the origin and mechanism(s) involved in H2S generation in the Montney Formation.

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