Petrographic and geochemical composition of kerogen in the Furongian (U. Cambrian) Alum Shale, central Sweden: Reflections on the petroleum generation potential

H. Sanei*, H. I. Petersen, N. H. Schovsbo, C. Jiang, Michael Evan Goodsite

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

This paper presents an integrated geochemical and petrological study of the Hällekis-1 core from the Furongian (upper Cambrian) Alum shales in central Sweden to characterise organic matter composition, depositional environment, and potential hydrocarbon generation capability. The results show that organic-rich Alum Shale (TOC: 8.9-28.0. wt.%) contains mainly immature, predominantly algal-derived kerogen with unusually reduced hydrocarbon generation potential as suggested by relatively low Hydrogen Index (HI) values (HI: 251-471. mg HC/g TOC) and high degree of aromaticity. In the absence of thermal generation of hydrocarbons in these immature shales, the recorded low HI values are explained by an unusual chemistry of the biota during the deposition of the Alum shale accentuated by a high degree of sustained bacterially-mediated degradation (e.g., sulphate reduction), and possibly intense nuclear degradation of labile kerogen by radiation from uranium-rich minerals. The higher degree of aromaticity in Alum shale suggests lower than expected oil-proneness. The results of this study suggest that the Alum Shale is a gas-prone source producing aromatic hydrocarbon mixtures with an unexpectedly low concentration of n-alkanes.

Original languageEnglish
JournalInternational Journal of Coal Geology
Volume132
Issue number1
Pages (from-to)158-169
Number of pages12
ISSN0166-5162
DOIs
Publication statusPublished - 1. Oct 2014

Keywords

  • Alum shale
  • Hydrocarbon potential
  • Hällekis-1 well
  • Kerogen
  • Sweden

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