内蒙古东部中上二叠统烃源岩地化特征与生烃潜力评价

GEOCHEMICAL CHARACTERISTICS AND HYDROCARBON-GENERATING POTENTIAL FOR MIDDLE-UPPER PERMIAN SOURCE ROCKS IN EAST INNER MONGOLIA

内蒙古东部地区是油气深部勘探的重点地区。为评价深部源岩层中上二叠统的油气资源前景,在野外地质勘查、典型剖面实测和样品分析测试的基础上,通过有机质丰度、类型、成熟度等地化指标,有机岩石学方法,生物标志化合物以及生烃热模拟实验,对中二叠统哲斯组和上二叠统林西组暗色泥质烃源岩的分布、地化特征和生烃潜力进行研究。研究表明:哲斯组为浅海—半深海相,林西组为近海湖盆—残余海相,两套地层均广泛发育巨厚层暗色泥岩;有机质丰度以中等—好烃源岩为主,类型主要为Ⅱ2—Ⅲ型,处于过成熟演化阶段,有机质以陆源高等植物和水生藻类等混源为主,沉积水体为具有一定盐度的强还原—还原环境;哲斯组和林西组具有一定的生气能力,最大生烃量分别达0.62 m3/t和2.48 m3/t。哲斯组和林西组作为潜在的气源岩,具有良好的天然气勘探前景。

East Inner Mongolia is the important region for the deep oil and gas exploration,in order to evaluate the hydrocarbon resources prospect of Upper Permian deep source rocks,on the bases of the field geological survey,typical profile measurement and sample analyses and tests,with the help of the geochemical indexes such as the organic matter abundance,type,maturity,etc. and moreover the organic petrology method,biomarkers and hydrocarbon-generating pyrolysis simulation experiment,the researches were conducted on the distributions,geochemicalcharacteristics and hydrocarbon-generating potential for the dark muddy source rocks in Middle Permian Zhesi and Linxi Formations. The study achievements show that the former is neritic-bathyal facies; the latter is paralic lacustrine basin-residual sea facies,the huge-thickness dark mudstones are widely developed in both formations; the organic matter abundances have generally reached the moderate to good standards of the hydrocarbon source rocks,the organic matter types are mainly shown as Type Ⅱ2-Ⅲ and have entered into the overmaturity stage,the organic matters are derived principally from the mixture of the continental-source higher plants,hydrobiontic algae and so forth,the sedimentary water bodies belong to the strong reduction-reduction environments with a certain salinity;Zhesi and Linxi Formation possess a certain amount of gas-generating capacity,the maximum hydrocarbon-generating quantity is 0. 62 m^3/t and 2. 48 m^3/t separately. Therefore,both of them are potential gas source rocks which much better favorable exploration prospects.