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Journal article
The Origins of the Hydrogen Sulphide (H2S) Gas in the Triassic Montney Formation, British Columbia, Canada
Geosciences, Vol.14(8), pp.1-23
2024
Abstract
The inexplicable distribution of souring wells (presence of H2S gas) of the unconventional Montney Formation hydrocarbon resource (British Columbia; BC) is investigated by analysing sulphur and oxygen isotopes, coupled with XRD mineralogy, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDX). The sulphur isotopic analysis indicates that the sulphur isotopic range for Triassic anhydrite (δ34S 8.9 to 20.98‰VCDT) is the same as theH2S sulphur that is produced from the Montney Formation (δ34S 9.3 to 20.9‰VCDT). The anhydrite in the Triassic rocks is the likely source of the sulphur in the H2S produced in the Montney Formation. The deeper Devonian sources are enriched in 34S and are not the likely source for sulphur (δ34S 17.1 and 34‰ VCDT). This is contradictory to studies on Montney Formation producers in Alberta, with heavier (34S-enriched) sulphur isotopic signatures in H2S gas of all souring Montney Formation producers. These studies conclude that deep-seated faults and fractures have provided conduits for sulphate and/or H2S gas to migrate from deeper sulphur sources in the Devonian strata. There are several wells that show a slightly heavier (34S-enriched) isotopic signature (δ34S 18 to 20‰VCDT) within the Montney Formation H2S gas producing within close proximity to the deformation front. This variation may be due to such deep-seated faults that acted as a conduit for Devonian sulphur to migrate into the Montney Formation. Our geological model suggests the sulphate-rich fluids have migrated from the Charlie Lake Formation prior to hydrocarbon generation in the Montney Formation (BC). Sulphate has concentrated in discrete zones due to precipitation in conduits like fracture and fault systems. The model fits the observation of multi-well pads containing both sour- and sweet-producing wells indicating that the souring is occurring in very narrow and discrete zones with the Montney Formation (BC). Government agencies and operators in British Columbia should map the anhydrite-rich portions of the Charlie Lake Formation, together with the structural elements from three-dimensional seismic to reduce the risk of encountering unexpected souring.
Details
- Title
- The Origins of the Hydrogen Sulphide (H2S) Gas in the Triassic Montney Formation, British Columbia, Canada
- Authors
- Gareth R L Chalmers (Corresponding Author) - University of the Sunshine Coast, Queensland, School of Science, Technology and EngineeringPablo Lacerda Silva - British Columbia Geological Survey (Canada, Victoria)Amanda Bustin - University of British ColumbiaAndrea Sanlorenzo - University of British ColumbiaMarc Bustin - University of British Columbia
- Publication details
- Geosciences, Vol.14(8), pp.1-23
- Publisher
- MDPI AG
- Date published
- 2024
- DOI
- 10.3390/geosciences14080224
- ISSN
- 2076-3263
- Copyright note
- © 2024 by the authors. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
- Data Availability
- The data supporting reported results can be found within this manuscript.
- Grant note
- This research was funded by Natural Sciences and Engineering Research Council of Canada (NSERC), grant number 533228-2018 and Geoscience BC, Project ID 2017-014.
- Organisation Unit
- School of Science, Technology and Engineering
- Language
- English
- Record Identifier
- 991054497402621
- Output Type
- Journal article
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