Abstract: Hydrocarbon migration always plays an important role in process of oil-gas accumulation. The south trough in Wuliyastai sag is char-acterized by small-sized and short-extending faults, poor plane connectivity of sandbodies under the control of sedimentary environrnent of subla-custrine fan, So lnconformity could be its dominant channel for hydrocarbon migration, and the hydrocarbons probably migrate along the conduct-ing systern composed of high porosity permeability sand body-secondary fanlt-unconformity. The sag has been found to possess static pressure system, vertically unified pressure system with formation pressure factor of about 1.0, horizontally more intensive pore fluid dynamic field to con-trol oil-gas migration directions. The study suggests that the oil gas reservoirs are mainly formed in low pressure areas with relative low energy.

Key words: Erlian basin, depression, conducting system, normal pressure, hydrocarbon migration