Organic biogeochemical study of deeper southeastern Bengal Basin sediments in West Bengal, India

Pravat Kumar Behera, Supriyo Kumar Das*, Devanita Ghosh, Devleena Mani, M.S. Kalpana, Minoru Ikehara, Priyank Pravin Patel

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

1 Citation (Scopus)
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Abstract

The Bengal Basin is a fluvio-deltaic basin spanning Bangladesh and part of east and northeast India. The evolution of the peripheral foreland basin has been studied, but published literature on depositional conditions, source and maturity of organic matter in the deeper sediments of the Indian section of the basin is rare, despite the fact that natural gas is often encountered during hydrocarbon exploration. Our research assesses the depositional environment and source of the organic matter (OM) in the Pleistocene-Miocene sediments from five wells drilled by Oil and Natural Gas Corporation Limited in the southeastern Bengal Basin, West Bengal, India and aims to understand its maturity and potential to yield natural gas. The total organic carbon/nitrogen ratio and stable isotope (δ13C and δ15N) signature indicate primarily aquatic and C3 terrestrial plant sources of the OM and deposition under tidal flat and marshy environments. The n-alkane and isoprenoid alkane distribution are consistent with an autochthonous source of OM and terrestrial oxic-suboxic shallow-water depositional setting. The Rock-Eval parameters, such as maximal pyrolysis temperature, hydrogen and oxygen indices, indicate the immature nature of Type III and Type IV kerogen. The presence of methanogenic archaea, as indicated by phylogenetic analysis, in two Miocene sediment samples from one well indicates an active microbial activity in Type III immature OM, derived from C3 marsh vegetation and deposited under oxic shallow-water conditions. Our research describes the presence of methanogenic archaea for the first time in Miocene Bengal Basin sediments and is one of the few reports of their presence in deep (> 4000 m) horizons.

Original languageEnglish
Article number104451
Number of pages18
JournalOrganic Geochemistry
Volume170
DOIs
Publication statusPublished - 2022

Bibliographical note

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Keywords

  • Alkanes
  • Bengal Basin
  • Kerogen type and maturity
  • Methanogenic archaea
  • Stable isotopes

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