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应用生物标志物分析技术,结合其他地球化学资料,对西藏羊湖盆地新生代雅西措群烃源岩的有机质生源构成、沉积环境和成熟度进行了讨论,结果显示:烃类有机组分包括正构烷烃、萜类、甾类和类异戊二烯烃等。分析图谱结果显示正构烷烃主峰为C23、C27、C29及C31,碳数分布范围很宽;OEP的平均值为4.56,Pr/Ph的平均值为0.24,植烷有明显优势。规则甾烷呈不对称的“V”字形分布,其C27/C29比值介于0.18～1.41之间。生物标志物特征指示了烃源岩中的有机物来源于菌藻类和高等植物输入,显示了较高盐度的还原性湖相沉积环境。甾烷成熟度参数C29ααα20S/ααα(20S+20R)值为0.046～0.382,C29αββ/(ααα+αββ)值为0.203～0.399,萜烷成熟度参数C3122S/(22S+22R)值约为0.415,结合其他指标综合判断,有机质演化主体处于低成熟-成熟阶段。
Biomass biogenic composition, sedimentary environment and maturity of the Cenozoic Yaxizuo Group source rocks in the Yanggupu Basin, Tibet, are discussed using biomarker analysis and other geochemical data. The results show that the organic components of the hydrocarbon include N-alkanes, terpenoids, steroids and isoprenoids. The results of the analysis showed that the main peak of normal paraffins was C23, C27, C29 and C31, and the distribution of carbon number was very wide. The average value of OEP was 4.56 and the average value of Pr / Ph was 0.24. The regular sterane has an asymmetric “V” shape with a C27 / C29 ratio of between 0.18 and 1.41. Biomarker characteristics indicate that organic matter in source rocks originates from bacterial algae and higher plant inputs, indicating a higher salinity reductive lacustrine depositional environment. The value of C29ααα20S / ααα (20S + 20R) was 0.046-0.382, the value of C29αββ / (ααα + αββ) was 0.203-0.399, and the value of pteridine maturity parameter C3122S / (22S + 22R) was about 0.415. Judging from other indicators, the main body of organic matter evolution is in a low maturity-maturity stage.