THE FEATURE OF MIGRATION AND ACCUMULATION FOR LARGE AND MEDIUM SIZED GAS FIELDS IN CHINA

There are different ways and forms for the migration and accumulation of natural sized gas in large and medium sized gas fields in major basins of China,which could be summarized as following:1.Regional tectonic movement is the most important factors for gas migration;2.Occurence of fluid potential controls the direction of gas migration and the place of accumulation;3.Natural gas is mainly migrated vertically and migrated step by step in a faulted basin,and is dominated by lateral migration in a craton,foreland or large fault sag basin,but with strong influence of vertical migration;4.Faults and unconformity surfaces are the major passways for gas migration;5.Abnormal high pressure is the drive force in high pressure basin,and thermal flow also shows some influence;6.Natural gas is normally accumulated in the updip of a basin and the paleo high.