Comparative Geochemical Evaluation of Oil Seeps East and West of the Qatar–Kazerun Fault, Southwest Iran

Document Type : Research Paper

Authors

1 Department of Geology, Faculty of Sciences, University of Isfahan, Isfahan, Iran

2 Department of Petroleum Geology and Sedimentary Basins, Faculty of Earth Sciences, Shahid Chamran University of Ahvaz, Ahvaz, Iran

3 Department of Paleontology and Geochemical Studies, Exploration Directorate, National Iranian Oil Company, Tehran, Iran

Abstract

This study presents a comparative geochemical assessment of oil seeps located east and west of the Qatar–Kazerun Fault in southwest Iran, with a focus on the Coastal Fars region and the southern Dezful Embayment. Eight seep samples were analyzed using whole-oil composition, biomarker parameters, and stable carbon isotopes to determine their genetic relationships, degree of secondary alteration, and correspondence with known subsurface reservoir oils. The results show that Coastal Fars seeps are sourced from a marine, reducing carbonate source rock of likely Lower Jurassic age. In contrast, Dezful Embayment seeps originate from the Lower Cretaceous Kazhdumi shale–marl source rock. Biodegradation ranges from mild in Kuh-e-Mand to severe in the Darang, Kardalan, and Dezful Embayment samples. The compositional similarity between Coastal Fars seeps and Asmari/Jahrum/Sarvak oils of Kuh-e-Mand, and between Dezful Embayment seeps and Asmari–Sarvak oils of the Embayment, demonstrates the dominant structural and stratigraphic control of the Qatar–Kazerun Fault on hydrocarbon generation, migration, and seep distribution. Ultimately, statistical analyses (PCA and HCA) confirm the presence of two genetically distinct oil families separated along the fault.

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References

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Journal of Petroleum Research
Volume 35, 1404-5 - Serial Number 144
January and February 2025
Pages 22-39

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