Petroleum geochemical characterization of the Middle Jurassic Sargelu oil shale, Zagros Mountains, Southwest Iran: Implications for petroleum system analysis

Articles in Press

Document Type : Research Paper

Authors

1 Institute of Petroleum Engineering (IPE), School of Chemical Engineering, College of Engineering, University of Tehran, Tehran, Iran

2 Department of Geosciences, University of Oslo, Oslo, Norway, P.O. Box 1047 Blindern, N-0316 Norway

3 Exploration Directorate, National Iranian Oil Company (NIOC), Tehran, Iran

Abstract

Two main oil shale intervals are recognized in the Qalikuh area of the Zagros Mountains in Lorestan Province, SW Iran: a lower oil shale in the Middle Jurassic Sargelu Formation, and an upper oil shale in the Early Cretaceous Garau Formation. In the present study, 50 outcrop samples of the Sargelu oil shale were collected from eight different localities and were subjected to a complete set of organic geochemical analyses. Samples of the Sargelu oil shale analysed exhibit high organic carbon (TOC) contents (mean: 15.5 wt%). The hydrogen index (mean: 548 mg HC/g TOC) and the genetic potential (mean: 86.20 mg HC/g rock) for the samples represent highly oil-prone kerogen. The Sargelu oil shale is enriched in sulfur, and elemental hydrogen has a moderate-to-high content. Organic petrography shows that the samples are dominated by solid bitumen and carbonate minerals, and X-ray fluorescence analysis shows that the main inorganic component of the oil shale is calcite. The palynofacies are characterized nearly entirely by amorphous organic matter. Kerogen in the Sargelu oil shale is Type II- S. In terms of thermal maturity, there is consistency between vitrinite reflectance, elemental analysis, and thermal maturity-related biomarker parameters which confirm that the Sargelu oil shale is located in the early stage of the oil window (Rc=0.8%). This study shows that there is little significant difference
in the geochemical and mineralogical properties of the Garau and Sargelu oil shales from Qalikuh, or in their respective pyrolysate products, despite the formations’ different stratigraphies and ages. However, compared to Garau-derived oils (extracts), the Sargelu-derived oils (extracts) demonstrate a higher ratio of dibenzothiophene to phenanthrene (DBP/Phen) and a lower ratio of C27/C29 sterane. These parameters can in future be used in oil - source rock correlation studies in locations where these formations are deeply buried and highly mature, and where the precise contribution of hydrocarbons from Sargelu and Garau source rocks to a reservoired petroleum is unknown

Keywords

Main Subjects

Article Title [Persian]

-

Geopersia

Articles in Press, Accepted Manuscript
Available Online from 19 October 2024

Files

History

  • Receive Date: 29 July 2024
  • Revise Date: 29 September 2024
  • Accept Date: 19 October 2024

Share

How to cite

Statistics