Geochemical Characteristics of Asmari, Sarvak and Khalij reservoirs in Pazanan and Khaviz Oil Fields Using Gas Chromatography and Gas Chromatography-Mass Spectrometry

In this study, two oil samples from Asmari and Sarvak reservoirs (well No#23) in Pazanan oil field and one oil sample from Khalij reservoir (well No#1) in Khaviz oil field were subjected to geochemical analyses using Gas Chromatography (GC) and Gas Chromatography Mass-Spectrometry (GC/MS) techniques. Quantitative assessment of the oil components using liquid chromatography method revealed that oil samples have a greater amount of saturated hydrocarbon component than the aromatic and polar. Classification of the crude oil samples based on different components shows that the Asmari and Sarvak reservoir oil in Pazanan oil field and Khalij reservoir oil in Khaviz oil field are paraffinic, mainly paraffinic to paraffinic - naphthenic and paraffinic – naphthenic respectively. The biomarker ratio obtained from C29 Sterane ββ∕(ββ+αα) versus C29 Sterane 20S/(20S+20R) diagram demonstrates that the oil samples were produced at the maximum stage of the oil producing window and have relatively high thermal maturity. The DBT/Phen versus Pr/Ph diagram shows that the Asmari oil samples have been produced from carbonate-shale, and Sarvak and Khlij oil samples have been produced from carbonate-marl source rocks. Also, triangular C27, C28, C29 sterane diagram indicates that the source rocks have been deposited in open marine to parallic environment. Also, oil has been generated from organic matter with type II kerogen as inferred from Pr/nC17 versus Ph/nC18 diagram. The proximity of the Carbon Preference Index (CPI) to the number 1, indicates high maturity level for source rocks. Absence of oleanane biomarker in oil samples suggests that oils be produced from lower-Cretaceous source rocks. Oil-oil correlation using distinctive biomarkers allowed to plot the stellar graph.  Finally, the even/odd ratio of normal alkanes determines that the oil samples from Asmari, Sarvak, and Khalij reservoirs have been produced from a variety source rocks.