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TitleMolecular and stable carbon isotope geochemistry of mud-gas-derived hydrocarbons and its application for the assessment of low-permeability reservoirs from the Montney Formation, Western Canada
AuthorCesar, JORCID logo; Mayer, B; Becker, V; Nightingale, M; Ardakani, O HORCID logo
SourceOrganic Geochemistry vol. 163, 104328, 2021 p. 1-7, Open Access logo Open Access
LinksOnline - En ligne
Alt SeriesNatural Resources Canada, Contribution Series 20210399
PublisherGeoConvention Partnership
Mediadigital; on-line
File formatpdf; html
ProvinceBritish Columbia
NTS93I; 93O; 93P; 94A; 94B; 94G; 94H; 94I; 94J
AreaFort St. John; Canada
Lat/Long WENS-123.0000 -120.0000 58.2500 54.5000
Subjectsfossil fuels; stratigraphy; geochemistry; sedimentology; Science and Technology; Nature and Environment; petroleum resources; hydrocarbons; hydrocarbon migration; stable isotope studies; carbon isotopes; petrographic analyses; stratigraphic analyses; core samples; pyrolysis; chromatography; mass spectrometer analysis; Montney Formation
ProgramGeoscience for New Energy Supply (GNES) Shale Reservoir Characterization
Released2021 10 08
AbstractMud-gas isotope logging (MGIL) of hydrocarbons (methane, ethane, propane) has become a widely used approach to fingerprint gas-bearing formations during the drilling of vertical and horizontal oil and gas wells often with the goal to assess potential cross-formational gas migration. In this study, we have used mud-gas molecular and isotope data to assess the usefulness of MGIL for the geochemical assessment of a single low-permeability reservoir formation, the Montney Formation in Western Canada. An example from a well completed in British Columbia shows that hydrocarbon samples collected in IsoJars® tend towards more positive carbon isotope ratios compared to data for samples obtained using IsoTubes®, potentially attributed to 13C enriched residual gas retained in the cuttings. Additionally, in publically available mud-gas data from 45 other wells, it was found that the carbon isotope ratios of mud-gas from the Montney Formation are overall consistent with the thermal maturity of this stratigraphic unit, but the data display a relatively scattered trend on a thermal maturity plot based on D13CC1-C2 and D13CC1-C3. Molecular parameters such as [C1/(C2 + C3)] can be modified via processes such as desorption and diffusion after sampling gases in IsoJars®, while the i-C4/n-C4 ratio was found to be the most consistent molecular parameter between sampling techniques. We conclude that mud-gas molecular and isotope data derived from samples collected in IsoTubes® are suitable for geochemical assessment (e.g. thermal maturity, fluid-fluid correlations) of low permeability hydrocarbon reservoirs such as the Montney Formation.
Summary(Plain Language Summary, not published)
In this study, we have used mud-gas molecular and isotope data to exemplify the limitations of mud-gas isotope logging (MGIL) for geochemical assessment of the Montney Formation low-permeability reservoirs. The caveats derive from isotopic fractionation, and more drastically, chemical fractionation that can be attribute to different sampling techniques. Although MGIL may have localized monitoring applications during drilling, we do not recommend their usage to establish robust geochemical interpretations unless other geochemical variables are well stablished.

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