ABSTRACT: The Darquain field is located in the Abadan Plain SW Iran, which has a high potential for exploration and production of hydrocarbon resources with poorly defined petroleum systems. The goal of this paper is to characterize the Cretaceous source rock potential in the Darquain field. A gamma-sonic log was used as a proxy to identify probable source rock zones and to select sample depths. A total of 37 samples were analyzed by Rock-Eval, elemental, Gas Chromatography (GC) and gas chromatographymass spectrometry (GC-MS) techniques. The petroleum generation potential, as well as origin of the organic matter of samples, have been investigated. The results of this study indicate that, in the Early Cretaceous successions, there are favorable source zones in Garau, Gadvan, and Kazhdumi Formations. These source zones predominantly contain organic matter from marine origin, suggesting kerogen type II, while some samples contain terrestrial organic matters, suggesting kerogen type III. The Lower Garau zone, with 1.14 to 14.29% total organic carbon (TOC), is an excellent source rock with a fair genetic potential in the range of 2.74 and 9.5 mg/g. Elemental analysis results in the Lower Garau zone allow the classification of kerogens as high-sulfur. There are very good source zones in the Kazhdumi Formation, with fair to good genetic potential. The results of Rock-Eval and petrophysical analyses show that gamma ray data can be used as a useful tool to determine the potential source zones, although where TOC is less than 1% there is inconsistency. The results obtained from the biomarker characteristics are in agreement with the results of Rock-Eval pyrolysis and indicated carbonate source rocks, which contain a mixture of marine organic matter with a minor amount of terrigenous organic matter. Biomarker characteristics also suggest that the organic matter was deposited in a marine environment under reducing conditions, and that Early Cretaceous source zones are at the stage of early oil window to peak of oil generation.

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