The n-alkane distribution of crude oils from the western Qaidam Basin is characterized by even-to-odd (C18-C28) predominance. Source rocks from the region are mainly characterized by odd-toeven predominance. Based on n-alkane distribution pattern, combined with single molecule carbon isotope analysis, comparing crude oil with source rock, it was discussed in this paper the main source rocks in the western Qaidam Basin. The correlation of n-alkane distribution and single molecule carbon isotope analysis illustrated that the chief hydrocarbon source layer was E23 and the secondary layers were E1+2 and E31 in deep region. Meanwhile, the chief hydrocarbon source layer was N1 and the secondary layer was N2 in shallow region. Hydrocarbon potential analysis showed that those samples with even-to-odd (C18-C28) predominance possessed higher TOC, bitumen "A", total hydrocarbon content and conversion ratio, displaying huge hydrocarbon generating potential.%柴西原油正构烷烃分布多呈偶奇优势(CPI<1),而烃源岩样品则多呈奇偶优势分布,只有少数呈偶奇优势分布.从正构烷烃分布模式出发,结合单体烃碳同位素分析,对柴西原油和烃源岩进行对比,以确定柴西原油形成的主力烃源岩.研究表明,柴西深层主力烃源层为E<'2><,3>,次要烃源层为E<,1+2>和E<'1><,3>;浅层主力烃源层为N<,1>,次要烃源层为N<,2>.从生烃性能角度看,正构烷烃分布呈偶奇优势的烃源岩样品,其有机碳、氯仿沥青"A"、总烃含量、转化系数等都比呈奇偶优势分布的样品高,生烃性能较好,应为柴西主力烃源岩.
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