Abstract: The deposits of shallw marine-littoral, lacustrine and fluvial facies of Upper Tiassic in west Sichuan depression occur with abundant oil-gas resources, which form a petroleum system dominated by natural gas. By using basin modeling technology, the hydrocarbon-generating history of source rocks and the compacting history of reservoirs in this depression are studied quantitatively. The started geologic age and peak reached period of hydrocarbon generation are pointed out. The determination of critical timing of hydrocarbon accumulation, including petroleum migration and accumulation areas, is made. The gas-generating quantity coresponding to the peak period and the paleostructure prior to reservoir compaction are restudied. Finally, the quantitative characteristice of the petroleum system are elaborated in this paper.

Key words: Sichuan, petroleum system, depression, Upper Triassic, simulation