Geochemical Evaluation of Source Rocks and Crude Oils of Marun Oil Field with Rock-Eval Pyrolysis (VI) and Gas Chromatography Instruments

Marun Oilfield is one of the main Iranian Oilfield in Dezful Embayment, Zagros area which was studied geochemically in this paper. Forty three samples from different source and reservoir rocks include Garue, Gadvan, Dariyan, Kazhdumi, Sarvak, Gurpi and Pabdeh formations from different oil wells were analyzed by Rock Eval VI. In addition, 23 selected extract bitumens and 6 crude oils of Bangestan and Khami reservoirs were studied by Liquid Chromatography and Gas Chromatography to compare with each other. Rock Eval data showed that Kazhdumi and Pabdeh formations with average TOC of 4.13 wt% and more than 12 mg HC/g rock amount of S2 had high hydrocarbon potential regard to other samples. HI vs. Tmax and S2 vs. TOC diagrams indicated that the Type II kerogen was the main type of kerogen in studied samples. Furthermore,Garue, Gadvan and Kazhdumi samples have high thermal maturity in compare with other samples. Also, variations of PI and Tmax versus depth indicate that Pabdeh and Gurpi samples had less thermal maturity in compare with Kazhdumi and Garue samples. Chromatograms study and variation of Pr/nC17 and Ph/nC18 indicate that studied samples have no or little evidence of biodegradation and crude oils of Bangestane and Khami reservoirs was formed in anoxic environment from the source rock with type II kerogen.