Abstract: The petroleum system subdivision is based on the critical process analysis of oil and gas from source to trap.In this process,the largest outside boundary of relatively independent oil and gas migration in the 3-D geological unit can be traced.The research on oil and gas migration plays the leading role in the subdivision.The composite petroleum system of China are characterized by multiple kitchens with multiple source rocks,multiple phases of hydrocarbon generation,migration and accumulation.Oil and gas were often migrated for many times since they had been generated from the kitchen.Some migration is from source kitchen to trap;some is the dispersion of the accumulated oil &gas;some is the adjustment from the former reservoir to new one.The identification direction of oil/gas migration in different stages can not only be used to distingaish the composile dependent petroleum system from independent according to the spatial relationships and extentence,and also to understand oil-gas preservation,dispersion,adjustment and occurrence.This paper emphasizes the importance of the study on oil-gas migration direction in the subdivision of composite petroleum systems.The key idea of the paper for tracing is suggested to follow the vine to get the milon,that is the process-oriented study.The oil and gas migration and accumulation unit can be therefore defined.And according to the relationships between these units,the largest outside boundary of the petroleum system can be finally outlined the direction of oil/gas dominant migration.

Key words: oil-gas migration, the direction of dominant migration, migration and accumulation unit, compos-ite petroleum systems

摘要： 含油气系统划分的核心是循着油气从源岩到圈闭的过程,追踪确定三维地质单元的相对独立的流体运动的最大外边界.其中油气运移研究居于重要地位.中国复合含油气系统表现为多源多灶多期生烃和成藏的复杂性.油气从生烃灶生成以后,往往发生了多次运移.有些是从生烃灶向圈闭的多次运聚过程;有些则是已聚集烃类的散失破坏;还有些则是油气从古油气藏向新油气藏的调整.对不同阶段油气运移流向的确定,既可划清含油气系统的交叉、共生与分立的空间关系和范围,又可了解油气保存与破坏规模及油气现今分布的有利地区.本文主要讨论复合含油气系统的划分要注重油气运移流向研究,在定源前提下,以顺藤摸瓜的方式,确定油气运聚单元.在此基础上,根据各运聚单元相互关系最终圈定含油气系统的最大外边界.

关键词: 油气运移, 流向, 过程恢复, 运聚单元复合含油气系统