Geochemical investigation and hydrocarbon generation–potential of the Chia Gara (Tithonian–Berriasian) source rocks at Hamrin and Kirkuk fields, Northwestern Zagros Basin, Iraq

Abstract

Abstract This study investigates the geochemical characteristics and hydrocarbon generation potential of the Chia Gara Formation (Tithonian–Berriasian) in the Northwestern (NW) Zagros Basin, Iraq. A comprehensive analysis of forty–seven extract samples and seven crude oil samples was conducted to evaluate the formation’s petroleum potential. The total organic carbon (TOC) content of the analyzed samples ranged from 0.68% to 3.95%, indicating fair to excellent source rock quality. Rock–Eval parameters revealed thermal maturity, suggesting an environment favorable for both oil and gas generation. Integrated analysis of TOC/Rock–Eval data, stable carbon isotope data, and biomarker parameters confirmed the existence of kerogen Type–II and mixed–II/III constituents, along with carbonate–rich deposits. These findings suggest deposition within an algal–dominant anoxic-marine environment. Characterization of crude oils from these fields revealed paraffinic types, further supporting the interpretation of the Chia Gara interval as the primary source rock in the NW Zagros Basin. The oil–source correlation strengthens the evidence, consolidating the formation’s significance in the region’s petroleum system.