Petroleum potential of Gurpi Formation and its role within the Cretaceous petroleum system, eastern Persian Gulf

The Gurpi Formation marls and shales in the eastern Persian Gulf display high gamma ray signatures on well logs, suggesting potential source rock behavior. This study assesses the hydrocarbon generation potential of Gurpi across the eastern Persian Gulf and its role in charging the Ilam reservoir. Ten oilfield samples were analyzed using Rock – Eval pyrolysis, GC, GC – MS, Py‑GC – MS, stable carbon isotope, elemental analysis, and visual kerogen petrography. One-dimensional basin modeling was applied to reconstruct burial, thermal, and maturation histories. Geochemical data indicate fair petroleum‑generation potential in southeastern localities (Sirri A, D, E, Nosrat, Farzam). Kerogen is dominated by Type II/III, deposited in a marine setting. Biomarker and isotopic signatures corroborate marine organic input and limited thermal alteration. Maturity indicators and basin models show Gurpi is largely immature within sampled fields but reaches early to peak oil‑window conditions in deeper structural depressions east of these fields. Although most sampled Gurpi intervals remain below effective generation thresholds, localized depocenters have likely generated and expelled hydrocarbons. Downward migration from these kitchens presents a plausible charge mechanism to the Ilam Formation. These results refine the regional petroleum system model and identify target areas where Gurpi sourced charge to Ilam reservoirs is most probable.