Genetic classification and geochemical evaluation of oil families in the South Dezful Embayment, southwest of Iran

Authors

1 Department of Geology, Faculty of Earth Sciences, Shahid Chamran University of Ahvaz, Ahvaz, Iran

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

Abstract

The occurrence of barren anticlines in the vicinity of major hydrocarbon fields producing from individual ‎reservoirs in the south of the Dezful Embayment unveils the structural complexity of the area and the ‎intricacy of the processes of hydrocarbon generation, migration and entrapment. In this study, we ‎investigate the possible genetic relationships between the Jurassic-Lower Cretaceous reservoirs on one ‎hand, and the Upper Cretaceous-Tertiary reservoirs on the other. A comprehensive geochemical approach ‎is undertaken to identify genetic oil families in the study area and throw some light on the existing ‎petroleum systems. Bulk geochemical properties and molecular fingerprints support the existence of two ‎distinct oil families within the Khami Group (Jurassic-Lower Cretaceous) and the Asmari-Sarvak (Upper ‎Cretaceous-Tertiary) reservoirs. Source and maturity related biomarker parameters well suggest differing ‎source rocks for these oil families. Oils in the Asmari-Sarvak family indicate a uniform thermal maturity ‎equivalent to the middle oil window. These oils have originated from a marly-carbonate source rock with ‎mixed marine-terrigenous organic matter input that was deposited under anoxic to semi-anoxic ‎conditions. The oils in the Khami Group family are derived from an older Early Cretaceous source rock ‎deposited under dysoxic to semi-anoxic conditions that could receive significant inputs of terrigenous ‎organic matter. These oils are most likely generated at the peak of oil generation window from their ‎parent source rock. Data from this study suggest that the immature Pabdeh Formation is a subordinate ‎source rock of the Asmari-Sarvak oil family that could play a minor impregnating role.‎

Keywords

References

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Advanced Applied Geology
Volume 10, Issue 2
July 2020
Pages 208-223

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