中国西部多旋回演化与油气聚集

POLYCYCLIC EVOLUTION AND PETROLEUM ACCUMULATION IN THE WEST OF CHINA

由额尔齐斯—得尔布干、康西瓦—龙木错—澜沧江两大岩石圈断裂所限定的广大西北地区的区域构造格架是由哈萨克斯坦板块和古中华陆板块中大小不等、属性不同的古陆块与多旋回造山带镶嵌交错排列而成,具有南北分带、东西分块特点。以海西早期运动、海西晚期运动、燕山中期运动为界线将西部区域构造与盆地演化划分为古亚洲洋体制下的震旦—中泥盆世开合旋回、古特提斯洋体制下的晚泥盆—中二叠世开合旋回、特提斯洋体制下的晚二叠世—晚侏罗世盆地旋回和现今大洋体制下的白垩纪以来的盆地旋回。按盆地的旋回性和改造程度可将西部盆地群分为弱改造多旋回盆地等六类。针对多旋回盆地多期形成的多种烃源在空间上并列、叠置、交错的复杂状况和复杂沉降及热体制下的多期生烃、排烃及运聚保存过程,完善了已有的复式油气系统的概念和分析内容,提出了油气成藏单元的概念并用于对复式油气系统内部不同部位成藏要素与过程的总结。在对已知油气藏解剖的基础上,系统分析了两大盆地中主要油气聚集带成藏的静态条件与动态过程,分别建立了成藏模式,强调西部油气聚集具有多源多期多灶供烃,两大类多成因储层和封闭系统形成、破坏与重建构成多种储盖组合,不同区带具有多类型圈闭纵、横向空间组合样式,存在多期聚集、破坏、调整等复杂过程。初步形成了从“古亚洲域和特提斯域的区域控制→多旋回盆地演化与多变的叠加改造方式→多源多期生烃形成多相态油气→复式油气系统中多类复式油气聚集带”的理论脉络。

Regional tectonic framework of the vast northwest area identified by 2 lithosphere fractures of Eerqisi-Deerbugan and Kangxiwa-Longmucuo-Lancangjiang is composed of polycyclic orogenic belt and ancient continental segment with different size and characteristics in the Kasakstan and Ancient China continental segments, belt-like in the south and north, block-like in the east and west. Bounded with early Hercynian movement, late Hercynian movement and middle Yanshan movement, regional tectonic framework and basin evolution can be divided into 4 cycles： the Sinian-Middle Devonian open-close cycle, under Ancient Asian Ocean environment; the Late Devonian-Middle Permian open-close cycle under Ancient Tethys Ocean environment; the Late Permian-Late Jurassic cycle under Tethys Ocean environment and the basin cycles since Cretaceous under present ocean environment. According to cycle characteristics and evolution degree, the west basins can be divided into 6 types such as mild conversion and polycyclic basin, etc. In this paper, the complicated space distribution of source generated in different stages, and the course of multi-stage hydrocarbon generation, chargement and accumulation in complicated deposition and thermal systems are discussed. The previous concept and content of multiple petroleum system are improved; a concept of petroleum accumulation unit is proposed and used in the summarization of accumulation element and course in different part of multiple petroleum system. Static condition and dynamic course of accumula- tion in 2 basins are analyzed based on dissection of previous reservoirs. An accumulation model is made. Petroleum accumulation in the west basins is characterized by multi-source and multi-stage. Formation, destruct and reformation of 2 types of various cause reservoirs and capping system result in sets of reservoir and cap. In different zone, types of trap compound horizontally and vertically. A general summary of ＂regional control of the Ancient Asia and Tethys→polycyclic basin evolution and changing superposition transformation→multi-facies oil and gas from multi-source and multi-stage hydrocarbon generation→types of multiple petroleum accumulation belt in multiple petroleum system＂ is put forward.