塔里木盆地志留系沥青砂岩的特性及其成因

CHARACTERISTICS AND GENESIS OF SILURIAN BITUMINOUS SANDSTONE IN THE TARIM BASIN

采用有机岩石学和有机地球化学相结合的方法，详细研究了塔里木盆地志留系沥青砂岩的特征及其成因。色质分析表明，志留系沥青砂岩含高的三环二萜烷且以Ｃ２３为主峰，与石炭系源岩不同，γ蜡烷含量不高，代表藻类生源的β胡萝卜烷含量较高，且具高孕甾烷、高重排甾烷的特征，反映沥青砂岩油源来自下古生界。有机岩石学研究表明，由于沥青砂岩含可溶性物质甚高，其油浸反射率（Ｒｂ为０２７％～０３６％）不能反映其真实成熟度，水浸反射率（Ｒｗ为１３５％～１５３％）与上下地层成熟度相吻合，排除了沥青砂岩“新生古储”的可能性。碳同位素分析结果进一步证实沥青砂岩源自下古生界的生油岩，是早古生代古油藏遭受后期构造破坏的结果。

The characteristics and genesis of Silurian bituminous sandstone in the Tarim Basin are detailedly studied by using the methods of organic petrology and geochemistry. The study results by GC MS show that the Silurian bituminous sandstone is characterized by the relatively high content of tricyclic diterpane with the main C 23 peak different from the Carboniferous source rocks, no high content of gammacerane, relatively high content of β carotane representing the algal source, high content of pregnane and rearranged sterane, which reflects the oil source of bituminous sandstone from the Lower Paleozoic strata. The data from organic petrology demonstrate that the bitumen reflectance in oil immersion( R b 0 27%～0 36%)can not reflect the true maturity of bituminous sandstone owing to the high content of soluble organic matter in it, while the bitumen reflectance in water immersion ( R w 1 35%～1 53%)is in accord with the country rock, the possibility of new formed and oil reservoired bituminous sandstone is ruled out. The data from carbon isotope δ 13 C further prove that the oil source of bituminous sandstone came from the Early Paleozoic oil pool destructed by late tectonics.