Petroleum system modeling in the central part of the Fars platform (Zagros Basin)

Abstract

The Fars Platform is a geological region with significant untapped potential for petroleum resources. Its unique structural and stratigraphic features, combined with favorable reservoir conditions, make it a key area for hydrocarbon exploration and production. To better delineate the Paleozoic petroleum system and mitigate future charge-related risks in the region, one- and two-dimensional petroleum system modeling was carried out. The primary objective of this study is to analyze the burial, thermal, maturation, and generation histories of the source rock(s), as well as the migration pathways, hydrocarbon charging history, and accumulation within reservoirs in the central part of the Fars Platform based on a comprehensive integration of geological, geophysical, and geochemical data. Geochemical investigation on potential source rocks showed that the Silurian hot shale of the Sarchahan Formation is the only effective source rock charging the Permian reservoir rocks. By conducting 1-D models in 6 wells, the maturation and hydrocarbon generation histories and also the heat flow for each well were obtained after calibrating the models with the measured temperature and vitrinite reflectance data. The resulting heat flows were consequently used in 2-D petroleum system modeling based on the interpretation of seismic data. The simulation results show that the occurrence of overpressure in the Dashtak Formation has caused the pressure to be different in the upper and lower layers, making this formation a suitable cap rock in the area. The hydrocarbons generated from the Sarchahan source rock started to expel in the eastern parts of the study area since the late Cretaceous, and expulsion occurred almost along the entire area during the Eocene. Before the Zagros orogeny happened in the Neogene, the hydrocarbon migration was mostly vertical while, after the orogeny, the lateral migration also occurred, mainly towards the regional high, and charged most of the traps. The large amounts of hydrocarbon, mostly in gaseous form, was expelled after the formation of structural traps. The results from this study can become the guideline for future exploration endeavors in the region to reduce risks and operational costs.