Sanei, H.2; Petersen, H. I.3; Schovsbo, N. H.4; Jiang, C.2; Goodsite, Michael Evan6
1 Institute of Technology and Innovation, Faculty of Engineering, SDU2 Geological Survey of Canada Calgary3 Maersk Oil, Exploration4 Geological Survey of Denmark and Greenland5 Faculty Administration - The Faculty of Engineering, Faculty of Engineering, SDU6 Faculty Administration - The Faculty of Engineering, Faculty of Engineering, SDU
Reflections on the petroleum generation potential
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.
International Journal of Coal Geology, 2014, Vol 132, Issue 1, p. 158-169
Alum shale; Hydrocarbon potential; Hällekis-1 well; Kerogen; Sweden