库车前陆盆地东西部油气成藏过程差异性分析——以吐北1和迪那2构造为例

Analysis of the difference in the hydrocarbon accumulation process between eastern and western parts of Kuqa foreland basin:Case study of Tubei 1 structure and Dina 2 structure

库车前陆盆地油气演化历史复杂,呈现多期生烃、多期运聚、破坏和调整并举、区带成藏具明显差异性等特点.由于分区对比研究较少,制约了对区带差异性油气分布规律的认识.因此,对库车前陆盆地东部和西部典型含油气构造进行对比分析,结合定量荧光、流体包裹体和油气运聚数值模拟等技术,系统地对比了库车前陆盆地东西部油气成藏过程差异性.①盆地西部聚集的轻质油组分以三环芳烃和四环芳烃为主,东部以四环芳烃为主,且部分储层段含有早期残余重质组分.②成藏过程具有"早油晚气,晚期规模成藏"特点,西部早期原油充注时间为15Ma左右,东部约为10Ma,西部烃源岩热演化明显高于东部.晚期西部成藏时间为3Ma左右,东部约为2.5Ma,强烈隆升的圈闭捕获了大规模的天然气和轻质油,成藏具有快速高效特点.③西部由于早期丧失了盖层的完整性导致原油散失,主要聚集晚期的天然气和少量轻质原油,东部继承性圈闭很好地聚集了2期油气充注.晚期,东部由于地层的翘倾导致油气向盐体上倾方向或浅部地层调整,形成次生油气藏或逸散.

It has multi-phase hydrocarbon generation and expulsion,migration and accumulation,adjustment and destruction in Kuqa foreland basin,and the reservoir forming process is complex and varies from region to region.There are few regional comparative studies,which restrict the understanding of region difference of hydrocarbon distribution.Two typical hydrocarbon bearing structure from east to west of Kuqa foreland basin were selected to make comparative analysis,by combining quantitative fluorescence technique,fluid inclusion analytical technique and 2D basin modelling technique.The difference of hydrocarbon accumula tion process in the Kuqa foreland basin were systematically compared.The result indicated:(1)The compo nent of light oil accumulated in the west was dominated by tricyclic and tetracyclic aromatics,while the east was dominated by tetracyclic aromatics.Some of the reservoir sections in the east contain residual heavy components from the early crude oil proved by QGF-E and TSF data.(2)The hydrocarbon charge process is characterized by uearly oil,late gas,and the gas charge is the most significantThe early oil charge time was about 15Ma in the west,10Ma in the east,and the thermal evolution of source rock is higher in the west than in the east.About 3Ma ago in the west and 2.5Ma ago in the east,the source rock entered gas generation stage.The trap uplifted sharply during the Himalayan orogeny,and the gas accumulated in the trap quickly and efficiently.(3)In the first stage,the migration pathway of hydrocarbon was vertically up ward and then laterally upward when reaching the salt bottom,the fault cut through the salt seal in the shallow burial,causing the leakage of the early oil.In the second stage,the trap in the west kept uplifting,while the east inclined causing the hydrocarbon to migrate to the updip direction and accumulate in the flank area of salt,shallow reservoir or seeping to the earth surface.