H2S-generation by methane-dominated TSR and carbon isotope fractionation in Lower Triassic Feixianguan Formation, Northeast Sichuan Basin

Chun Fang Cai*, Liu Lu Cai, Jun Zhang, Xun Au Cai, Kai Kai Li

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    14 Citations (Scopus)

    Abstract

    Melhane-dominaled TSR has been proposed lo occur in Lower Triassic Feixianguan Formation oolilic dolomite reservoirs on ihe northeast side lo the Kaijiang-Liangping basin (Cai et al., 2004), but not in oolilic limestone on the southwest side where there is no significant H2S and low porosity. TSR-calcile is shown lo have δ13C values mainly from - 10‰ to - 29‰ and coexists with solid bitumen, elemental sulfur, pyrile and quartz, and has replaced dolomite, anhydrite and celeslile. However, present CO2 gas has δ13C values mainly from -2‰ to +2‰, suggestive of dissolution of carbonates (likely dolomite) after TSR-calcile precipitation, Malural gases from Changxing Fm, Feixianguan Fm. and Jialingjiang Fm. from the Fast lo Puguang gasfield show a logarithmic relationship between methane δ13C1 and residual hydrocarbons (HCs). Based on this relationship, it can be calculated that about 15% methane of well Du4 gas from the Feixianguan Fm. may have been oxidized as the result of TSR.

    Original languageEnglish
    Pages (from-to)889-894
    Number of pages6
    JournalActa Petrologica Sinica
    Volume28
    Issue number3
    Publication statusPublished - 2012

    Keywords

    • Carbon isotopes
    • Dolomite dissolution
    • Methane
    • Porosity
    • Sichuan Basin
    • Thermochemical sulfate reduction (TSR)

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