关键词: 油气运移, 成藏机理, 异常压力, 含气系统, 流体封存箱

Abstract: Based on the characteristics of natural gas generation and distribution as well as the that of formation pressures in the east part of Sichuan Basin,migration and accumulation mechanism of natural gas in Silurian-Carboniferous petroleum system in the area is studied in the paper. There are two kinds of model for forming gas pools both in the abnormally pressured compartment and out the compartment in the system.After the breakage of overpressured fluid compartments in Silurian system,hydrocarbons generated in the compartments flowed to Carboniferous in a phase of mixed fluids. Within Carboniferous system, hydrocarbons migrated to the crest part of the existed uplift traps and formed primary oil and gas accumulation which then were changed into gas pools with their further buring. A large scale migration and accumulation took place during Later Himalayan movement,as a result a type of called remained gas pools with higher gas columns were formed. The water displacement experiment of Carboniferous gas showed that under normal pressure natural gas in subsurface reservoir is difficult to migrate into minor pores and displaced water out the pores in reservoir. Obviously this kind of gas reserved in minor pores migrated in early stage. The dissolution convection may be an important mechanism for the migration and ccumulation of gas pools.

Key words: migration of hydrocarbon, formation mechanism for hydrocarbon pools, abnormally formation pressure, natural gas system, abnormally pressured fluid compartments