准噶尔盆地中部地区混源原油正构烷烃氢同位素特征及地质意义OA

[Objective]The geological conditions in the Junggar Basin hinterland are diverse,and the crude oil properties are complex.To address the issues of crude oil type classification and oil and gas source identification in this area,a study was conducted on the hydrogen isotopic characteristics of n-alkanes(δ2Halk)in the mixed-source crude oils from the Junggar Basin hinterland.[Methods]Gas Chromatography-Mass Spectrometry(GC-MS),Gas Chromatography-Isotope Ratio Mass Spectrometry(GC-IRMS)and Gas Chromatography-Thermal Conversion-Isotope Ratio Mass Spectrometry(GC-TC-IRMS)techniques were employed to analyze biomarker compounds and conduct hydrogen isotope analysis of n-alkane monomers in 33 crude oil samples from different strata.[Results]Three types of crude oil were identified in the Junggar Basin hinterland:Type I originated from the Jurassic coal-bearing source rocks(J1b),with the lightest hydrogen isotopic composition due to the significant input of terrestrial higher-plant organic matter;Type II mainly originated from the Permian Fengcheng Formation source rocks(P1f),with Type IIA derived from lacustrine sedimentary environments in transitional marine-terrestrial settings,featuring a low Ga/C30H ratio and relatively heavy hydrogen isotopic composition,while Type IIB had a lighter hydrogen isotopic composition and a higher Ga/C30H ratio;Type III crude oil mainly originated from the Permian Lower Wuerhe Forma-tion source rocks(P2w),with a light hydrogen isotopic composition of n-alkanes.[Conclusions]The combination of hydrogen isotopic analysis of n-alkanes and biomarker compound analysis is able to precisely classify crude oil types and clarify their sources,which is highly significant for oil source tracking and crude oil classification throughout the Junggar Basin.