准噶尔盆地西北缘风城组烃源岩热演化生物标志化合物变化及意义

以准噶尔盆地西北缘玛湖凹陷二叠系风城组泥质烃源岩为研究对象，通过封闭体系热模拟实验，以热模拟温度为成熟度标尺，对风城组烃源岩的典型生物标志化合物判识参数，如姥植比、Pr/nC₁₇、β-胡萝卜烷绝对含量、C₂₀、C₂₁和C₂₃三环萜烷分布样式以及孕甾烷与规则甾烷比值等，进行不同成熟度阶段的生物标志化合物演化特征及其适用范围的研究，以期通过与盆1井西凹陷的原油进行对比，更加准确地判识盆地西北缘风城组来源的高熟油气。结果表明，除C₂₀、C₂₁与C₂₃三环萜烷的分布样式外，姥植比、Pr/nC₁₇、β-胡萝卜烷绝对含量等参数受成熟度影响较大，不能用作高熟凝析油气的来源判识。通过在油源对比分析过程中加入成熟度因素的考量，结合新建立的风城组烃源岩正构烷烃单体碳同位素图版，对盆1井西凹陷盆5井来源有争议的高熟凝析油进行对比分析，推测其主要来源于风城组烃源岩。

Changes and Significance of Biomarkers in Thermal Evolution of Fengcheng Formation Source Rocks in Northwestern Margin of Junggar Basin

A thermal simulation experiment in a closed system was conducted on the cores of argillaceous source rocks in the Permian Fengcheng formation of the Mahu sag in the northwestern margin of the Junggar basin. Taking the thermal simulation temperature as a scale，the evolution characteristics and applicable ranges of the biomarkers in different stages of maturity were analyzed in light of the parameters for identifying typical biomarkers in the Fengcheng formation source rocks，which includes Pr/Ph，Pr/nC₁₇，absolute content of β-carotane，distribution patterns of C₂₀，C₂₁ and C₂₃ tricyclic terpenes，and ratio of pregnane to regular sterane. On this basis，it is expected to more accurately identify the high-matured oil and gas from the Fengcheng formation in the northwestern margin of the Junggar basin by comparing with the crude oil in the West Pen-1 sag. The results show that，in addition to the distribution patterns of C₂₀，C₂₁ and C₂₃ tricyclic terpenes，the typical oil-source correlation parameters of the Fengcheng formation such as Pr/Ph，Pr/nC₁₇，and absolute content of β-carotane are greatly affected by maturity and cannot be used to identify the source of high-matured condensate oil and gas. By considering the maturity in the process of oil-source correlation and combined with the newly established carbon isotope chart of normal alkane monomers for the Fengcheng formation source rocks，the controversial high-mature condensate oil from Well Pen-5 in the West Pen-1 sag was analyzed. It is speculated that the condensate oil from Well Pen-5 mainly came from the Fengcheng formation source rocks.