Geochemical Study of Sarvak Oil Reservoirs in the Persian Gulf

The Sarvak Formation is known as one of the largest sources of crude oil in the Persian Gulf region. In this study, 28 oil samples were collected from the Sarvak reservoirs and analyzed based on geochemical data in order to determine the genetic relationship of oils, depositional environment of source rocks and its dominant conditions, thermal maturity and source rocks age. Using the geochemical parameters, the depositional environments of source rocks have been determined, which include the marine carbonate environment, mixture of marine shale and carbonate, and marine carbonate-marl environment. The chemical conditions of the depositional environments have been evaluated based on the biomarker data, thus the redox conditions of the depositional environments are determined the anoxic marine environment. According to the Gammacerane index and Moretane/C30 Hopane ratio, the water column stratification and salinity of the depositional environment were assessed, thus the source rocks depositional environments are determined the normal water salinity and non-stratified marine to low water salinity/stratification marine. The thermal maturity of oils has been determined based on the study of biomarkers including the terpenes and steranes. Therefore, the samples are determined in the mature oils range, and the most of source rocks are located at the beginning of the oil window. The C28/C29 steranes ratio suggests the Paleozoic and Jurassic source rocks for the central Persian Gulf samples (BL-A, BL-B, RE-A, NT-C and RD-A), while the Sarvak reservoir in other parts of this region is sourced from the Cretaceous carbonate source rocks.