Geochemical characterization and origin of the Cretaceous Sa’di, Khasib, Mishrif, and Nahr Umr Crude Oils in Halfaya Oilfield, Southern Mesopotamian Basin, Iraq

Abstract

A suite of crude oil samples from the Cretaceous reservoirs in Halfaya Oilfield, Southern Iraq were analyzed using organic geochemistry analysis to study their geochemical characterization and origin. High sulfur content (3.74 ± 1 wt.%), C22/C21, C29/C30 hopane, ratios, and low C19/C23 and C24/C23 for all oil samples are indicators of marine carbonate environment source. Low pr/ph, Pr/nC17, Ph/nC18, and highest C35S/C34S ratio are consistent with a more reducing carbonate depositional environment. The C28/C29 sterane ratio and stable carbon isotope analysis values of crude oils are suggested Upper Jurassic to Middle Cretaceous anoxic marine carbonate source origin.