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TitleDiagenetic fluid flow and hydrocarbon migration in the Montney Formation, British Columbia: fluid inclusion and stable isotope evidence
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorKingston, A WORCID logo; Ardakani, O HORCID logo
SourceGeological Survey of Canada, Scientific Presentation 145, 2022, 29 pages, Open Access logo Open Access
PublisherNatural Resources Canada
Mediadigital; on-line
File formatpdf
ProvinceAlberta; British Columbia
NTS83B; 83C; 83D; 83E; 83F; 83G; 83J; 83L; 83M; 83N; 83O; 84B; 84C; 84D; 84E; 84F; 84G; 84I; 84J; 84K; 84L; 84M; 84N; 84O; 84P; 93G; 93H; 93I; 93J; 93O; 93P; 94A; 94B; 94G; 94H; 94I; 94J; 94O; 94P
Lat/Long WENS-123.8333 -113.8333 60.0000 52.8333
SubjectsScience and Technology; general geology; isotopes; hydrocarbons; Montney Formation; Triassic
Illustrationsphotographs; diagrams; location maps; photomicrographs
ProgramEnergy Geoscience Clean Energy Resources - Decreasing Environmental Risk
Released2022 11 01
The Montney Formation in Alberta and British Columbia, Canada is an early Triassic siltstone currently in an active diagenetic environment at depths greater than 1,000 m, but with maximum burial depths potentially exceeding 5,000 m (Ness, 2001). It has undergone multiple phases of burial and uplift and there is strong evidence for multiple generations of hydrocarbon maturation/migration. Understanding the origin and history of diagenetic fluids within these systems helps to unravel the chemical changes that have occurred since deposition. Many cores taken near the deformation front display abundant calcite-filled fractures including vertical or sub-vertical, bedding plane parallel (beefs), and brecciated horizons with complex mixtures of vertical and horizontal components. We analyzed vertical and brecciated horizons to assess the timing and origin of fluid flow and its implications for diagenetic history of the Montney Fm. Aqueous and petroleum bearing fluid inclusions were observed in both vertical and brecciated zones; however, they did not occur in the same fluid inclusion assemblages. Petroleum inclusions occur as secondary fluid inclusions (e.g. in healed fractures and along cleavage planes) alongside primary aqueous inclusions indicating petroleum inclusions post-date aqueous inclusions and suggest multiple phases of fluid flow is recorded within these fractures. Raman spectroscopy of aqueous inclusions also display no evidence of petroleum compounds supporting the absence or low abundance of petroleum fluids during the formation of aqueous fluid inclusions. Pressure-corrected trapping temperatures (>140°C) are likely associated with the period of maximum burial during the Laramide orogeny based on burial history modelling. Ice melt temperatures of aqueous fluid inclusions are consistent with 19% NaCl equiv. brine and eutectic temperatures (-51°C) indicate NaCl-CaCl2 composition. Combined use of aqueous and petroleum fluid inclusions in deeply buried sedimentary systems offers a promising tool for better understanding the diagenetic fluid history and helps constrain the pressure-temperature history important for characterizing economically important geologic formations.
Summary(Plain Language Summary, not published)
In this study we measured the pressure-temperature-composition characteristics of fluid inclusions in calcite-filled fractures in combination with stable isotope geochemistry of the host calcite to evaluate diagenetic fluid flow through the Montney Formation. We found evidence of two major fluid flow events with the latter associated with the thermal degradation of hydrocarbons in a closed system. Both fluid flow events occurred during peak burial ~50Ma likely around 140 degrees C. This work has implications for the timing of hydrocarbon migration and their thermal maturation within the Montney Formation.

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