Abstract: To solve a difficult problem of direct correlation between condensate in a reservoir and bitumen remaining in the source rock-compositionalsegregation caused by their existence in different phases. Taking the Xujiahe Ⅱ condensate reservoir in Zhongba structure of northwestern Sichuan basin as an example and this paper gives a careful study of the characteristics of biomarker distribution in the bitumen from the reservoir, and then it is compared with the biomarkers of related source rocks and condensate in Xujiahe Ⅱ formation. Correlations of reservoir bitumen-source rock and reservoir bitumen-condensate show clearly that the condensate in Xujiahe Ⅱ is come from the upper Xujiahe Ⅰand Xujiahe Ⅲ. The fact that lower molecular weight biomarkers are highly rich in reservoir bitumen and some muddly siltstone shows further that in this local area the reasonable mechanism of migration is that hydrocarbons migrate mainly as gas phase.

摘要： 为了解决凝析物与源岩直接对比中的难题——由于存在相态不同引起的成份分异,本文以川西北中坝须二段凝析气藏为例,重点研究了须二段气藏储层沥青的生物标志物分布特征,然后再与有关生油岩和须二段凝析油的生物标志物作了比较。特别用倍半萜、二萜进行储层沥青-源岩,储层沥青-凝析物的对比,结果证明须二段的凝析油是来自须一段上部和须三段。从低分子量生物标志物在储层沥青和一些泥质粉砂岩中的大量富集,进一步证实了该区成烃以气相运移为主的机制是合理的。