乌拉尔前陆盆地带大油气田形成条件与分布规律

Formation and Distribution of Giant Oil Gas Fields in Ural Foreland Basin Belt

乌拉尔前陆盆地带包括蒂曼—伯朝拉盆地和伏尔加—乌拉尔盆地。该区油气资源十分丰富,目前共发现大油气田28个,为俄罗斯重要的油气生产基地。应用含油气系统评价的方法,通过对乌拉尔前陆盆地的形成演化和石油地质特征的分析,并对典型油气田进行剖析,探讨了主要油气田的形成条件和分布规律。研究认为,在晚泥盆世弗拉斯期-法门期被动大陆边缘阶段,快速沉降时发育良好的多马尼克组烃源岩,岩性主要为泥岩、泥灰岩,为整个盆地带最主要的烃源岩;储集层主要为泥盆—二叠系浅水陆架相的碳酸盐岩和碎屑岩;受海西期乌拉尔造山运动的影响,盆地不断抬升,二叠系空谷阶发育良好的区域性膏岩盖层;该盆地带主要发育构造圈闭,其次为构造-地层复合圈闭;受盆地差异沉降的影响,不同地区的烃源岩热演化程度不同,最早的油气生成期为早石炭世;油气主要沿断裂和不整合面运移;油气主要分布在古隆起及其周围斜坡带。研究区的油气勘探处于勘探中期,但蒂曼—伯朝拉盆地的海域部分,伏尔加—乌拉尔盆地的中部、北部和南部勘探程度较低,具有很大的勘探潜力。

Ural foreland basin belt includes Timan-Pechora and Volga-Ural basins with very rich hydrocarbon resources,in which 28 giant oil-gas fields have been found up to now.So it is an important base for hydrocarbon production in Russia.This paper uses the method of petroleum system evaluation,analyzes the evolution and petroleum geologic characteristics of the foreland basin,interprets the typical oil-gas fields and summarizes the formation conditions and distribution of the fields.It is suggested that in the stage of passive continental margin of Frasnian to Famennian period of Late Devonian,Domanik hydrocarbon source rock with shale and marl was deposited in the foreland basin,which became the most important source rock in this belt.The reservoir is mainly distributed in the Neopaleozoic,and the lithology was carbonate rock and clastic rock deposited in the shallow shelf.Under the influence of Ural orogeny,the basin was in ceaseless uplifting and the regional gypsolyte cap rock was formed in Kungurian of the Permian.In the basin belt,structural traps were mainly developed,and then structural-stratigraphic traps.Influenced by the basinal differential subsidence,the source rocks in different areas are different in thermal evolution extent,and the earlist hydrocarbon generation period was in Early Carboniferous.Hydrocarbon migration occurred mainly along faults and unconformity,and hydrocarbon distribution around the palaeohighs and their slopes.The study shows that the petroleum exploration is in middle stage in this area,but in the offshore of Timan-Pechora basin and the central,the northern and southern parts of Volga-Ural basin,their low explorative extents make them have great exploration potentials.