鄂尔多斯盆地上古生界煤系烃源岩三环萜烷成因探讨
- 收稿日期:
2023-05-17
- 网络出版日期:
2024-04-09
摘要: 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气相色谱和色谱-质谱分析，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C19TT为主峰，C19TT、C20TT、C21TT含量逐渐减小的变化趋势，同时该类样品中Pr/Ph比值高，C24四环萜烷含量也较丰富，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C23TT为主峰，C19TT、C20TT、C21TT含量是逐渐增大的，而Pr/Ph比值低，C24四环萜烷含量不丰富，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类烃源岩差异迥然；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C23TT，另一方面C19TT、C20TT、C21TT相对含量又依次降低并呈阶梯状分布的特征，此外Pr/Ph比值和C24四环萜烷的含量均介于Ⅰ类烃源岩和Ⅱ类烃源岩之间。研究结果还揭示了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，也就是说，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。
Composition Characteristics And Genesis Of Tricyclic Terpanes In Upper Paleozoic Coal Measure Source Rocks In Ordos Basin
- Received Date:
2023-05-17
- Available Online:
2024-04-09
Abstract: The saturated hydrocarbons of 26 coal measure source rock samples in the Upper Paleozoic of Ordos Basin were analyzed by gas chromatography and chromatography-mass spectrometry. According to the distribution characteristics of tricyclic terpanes (TT), the source rock samples in the study area were divided into three different types of distribution patterns. The C19TT is the main peak of the type I source rock, and the content of C19TT, C20TT and C21TT gradually decreases. At the same time, the Pr/Ph ratio is high and the content of C24 tetracyclic terpane is also rich in this type of sample. This kind of samples are mainly humic coal and carbonaceous mudstone, revealing the characteristics of lacustrine facies sedimentary environment. On the contrary, the tricyclic terpanes of type II source rocks are dominated by C23TT, and the contents of C19TT, C20TT and C21TT are gradually increasing, while the Pr/Ph ratio is low, and the content of C24 tetracyclic terpane is not abundant. In addition to coal-bearing mudstone, there are also humic coal and carbonaceous mudstone in these samples, and their sedimentary environment is quite different from that of type I source rocks. The distribution of tricyclic terpanes in type III source rocks is between type I and type II source rocks. On the one hand, the main peak carbon of tricyclic terpane is C23TT, on the other hand, the relative content of C19TT, C20TT and C21TT decreases in turn and shows the characteristics of stepwise distribution. In addition, the Pr/Ph ratio and the content of C24 tetracyclic terpane are between type I and type II source rocks. The results also reveal that with the increase of the thermal evolution degree of source rocks, the total amount of tricyclic terpanes shows an gradually increasing trend, but the distribution patterns of tricyclic terpanes in different types of source rocks have not changed significantly, in other words, the different distribution patterns of tricyclic terpanes in coal-bearing source rocks in the study area are less affected by the thermal evolution degree of organic matter, but mainly controlled by sedimentary environment and parent material type.
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