Lower Jurassic Source Rock Contribution on Cretaceous and Tertiary Reservoirs Hydrocarbon Filling of Oil Fields, North West Persian Gulf, Iran

In the first comprehensive study of the Northwest margin of Persian Gulf basin petroleum system of offshore Southwest Iran, we test oil–source rock correlation through molecular biomarker and Carbon Isotope analysis of oil samples from wells scattered throughout the region, as well as purported source rocks. The chemical compositions of 11 crude oils and 9 extracts of potential source rocks from the Bahregansar-Hendijan High and two adjacent fields of the North West Persian Gulf sedimentary Basin, Iran were studied in detail by geochemical methods in order to understand their genetic relationship. The oil samples were collected from the all producing fields. The rock samples studies, selected after Rock-Eval pyrolysis screening of a large suite of samples, consist of 32 shale samples distributing from Lower Cretaceous up to Lower Tertiary in the stratigraphic column of the studied oilfield. The new data presented in this manuscript suggest that the oils constitute two oil families, and that the source rock was predominant marine shale deposited in an oxic to suboxic environment. Possible source rocks were selected and analyzed from different wells and compared with the oils. A negative correlation suggests that Upper Cretaceous intervals of limestone, marl, and black shale previously believed to be important source rocks can be discounted as an important contributor to Northwest Persian Gulf basin oils. Instead, the new data suggest a Lower Jurassic source rock contribution in charging Cretaceous and Tertiary reservoirs of Soroush, Abouzar, Nowroz and Arash oil fields.