鄂尔多斯盆地上古生界煤系烃源岩三环萜烷成因探讨  

Origin of Tricyclic Terpane in the Upper Paleozoic Coal-measure Source Rocks in the Ordos Basin

作　　者：林舒敏 张敏 李洪波[1,2] LIN ShuMin;ZHANG Min;LI HongBo(Hubei Key Laboratory of Petroleum Geochemistry and Environment(School of Resources and Environment,Yangtze University),Wuhan 430100,China;Key Laboratory of Exploration Technologies for Oil and Gas Resources(Yangtze University),Ministry of Education,Wuhan 430100,China)

机构地区：[1]油气地球化学与环境湖北省重点实验室(长江大学资源与环境学院),武汉430100 [2]油气资源与勘探技术教育部重点实验室(长江大学),武汉430100

出　　处：《沉积学报》2024年第4期1433-1446,共14页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(42072165)。

摘　　要：【目的】鄂尔多斯盆地煤系烃源岩发育,其饱和烃中三环萜烷含量丰富,但其三环萜烷分布模式在研究区表现出较大的差异性,因此探讨其差异性的主控因素具有重要意义。【方法】利用气相色谱和色谱—质谱分析技术,对鄂尔多斯盆地上古生界26个煤系烃源岩样品饱和烃进行了详细地剖析。【结果】根据三环萜烷(TT)的分布特征将研究区烃源岩样品划分为三种不同类型的分布模式。Ⅰ类烃源岩以C_(19)TT为主峰,C_(19)TT、C_(20)TT、C_(21)TT含量逐渐减小的变化趋势,同时该类样品中Pr/Ph比值高,介于1.19~3.84,平均值为2.99、C_(24)四环萜烷含量也较丰富,C_(24)四环萜烷/C_(26)TT比值介于2.39~32.54,平均值为9.80、C_(28)三环萜烷和C_(29)三环萜烷缺失,这类样品主要是腐殖煤和炭质泥岩,揭示出湖沼相沉积环境之特征;与之相反的Ⅱ类烃源岩的三环萜烷以C_(23)TT为主峰,C_(19)TT、C_(20)TT、C_(21)TT含量是逐渐增大的,而Pr/Ph比值低,比值主要介于0.34~0.90,平均值为0.61、C_(24)四环萜烷含量不丰富,C_(24)四环萜烷/C_(26)TT比值主要介于0.42~0.77,平均值为0.54、C_(28)三环萜烷和C_(29)三环萜烷含量丰富,这类样品除了煤系泥岩之外还有腐殖煤和炭质泥岩,其沉积环境与Ⅰ类烃源岩迥然不同;Ⅲ类烃源岩的三环萜烷分布介于Ⅰ类和Ⅱ类烃源岩之间,一方面三环萜烷的主峰碳为C_(23)TT,另一方面C_(19)TT、C_(20)TT、C_(21)TT相对含量又依次降低并呈阶梯状分布的特征,此外Pr/Ph比值为2.07、C_(24)四环萜烷/C_(26)TT比值为3.53,两者均介于Ⅰ类烃源岩和Ⅱ类烃源岩之间。【结论】随着烃源岩热演化程度的增加,三环萜烷的总量展示了逐渐增大的变化趋势,但不同类型烃源岩的三环萜烷分布模式并没有发生明显变化,说明研究区煤系烃源岩三环萜烷的不同分布模式受有机质热演化程度影响较小,而主要受控于沉积环境和母质类型�[Objective]Coal-measure source rocks in Ordos Basin are developed,and the content of tricyclic terpane in saturated hydrocarbons is rich.However,the distribution patterns of tricyclic terpane show important dif⁃ferences in the study area.Therefore,it is of great significance to explore the main controlling factors for these differ⁃ences.[Methods]Saturated hydrocarbons of 26 coal-measure source rock samples in the Upper Paleozoic of the Ordos Basin were analyzed in detail by gas chromatography and chromatography⁃mass spectrometry.[Results and Discussions]According to the distribution characteristics of tricyclic terpanes(TTs),the source rock samples in the study area were divided into three types of distribution patterns.The C_(19)TT is the main peak of the typeⅠsource rock,and the content of C_(19)TT,C_(20)TT and C_(21)TT gradually decreases.At the same time,the Pr/Ph ratio is high,and the ra⁃tio distribution range is between 1.19 and 3.84,with an average value of 2.99.The content of C_(24)tetracyclic terpane is also rich in this type of sample.The ratio distribution range of C_(24)tetracyclic terpane/C_(26)tricyclic terpane is between 2.39 and 32.54,with an average value of 9.80.Both C_(28)tricyclic terpane and C_(29)tricyclic terpane are absent.This kind of sample is mainly humic coal and carbonaceous mudstone,revealing the characteristics of a lacustrine facies sedimentary environment.By contrast,the tricyclic terpanes of typeⅡsource rocks are dominated by C_(23)TT,and the content of C_(19)TT,C_(20)TT and C_(21)TT gradually increases,whereas the Pr/Ph ratio is low and the ratio distribution range is mainly within the range of 0.34 and 0.90,with an average value of 0.61.The content of C_(24)tetracyclic terpane is not abundant,and the ratio distribution range of C_(24)tetracyclic terpane/C_(26)tricyclic terpane is mainly between 0.42 and 0.77,with an average value of 0.54.Both the C_(28)tricyclic terpane and C_(29)tricyclic terpane are abundant.In addition to coal-measure mudstone,humic coal and carb

关 键 词：三环萜烷 主控因素 沉积环境 煤系烃源岩 鄂尔多斯盆地 

分 类 号：P618.13[天文地球—矿床学]