The whole oilGC/MS analysis shows thatmolecular constituents of oil in theWen’an oilfield in the Jizhong area have certain heterogeneity.According to this study，it is believed that at least two genetic types ofoil（TypeⅠand TypeⅡ）occur in theWen’an oilfield.The TypeⅠoil is characterized by relatively high steˉraneˉhopane ratio，relatively higher content of biomarkers（sterane，gammacerane and4ˉmethyl sterane）and reˉlatively lower content of aromatic compounds（methylphenanthrene，triaromatic sterane and methyldibenzothioˉphene）.In contrast，the TypeⅡoil features in lower steraneˉhopane ratio，relatively lower content ofbiomarkers and relatively higher contentof aromatic compounds.The distribution of these two types ofoil shows certain reguˉlarity，with the typeⅠoil occurring in the Yilunpu structural belt in the southern part and the TypeⅡoil disˉtributed in the Shigezhuang structural belt in the northern part.At least two petroleum systems occur in the Wen’an oilfield.