Abstract: Sanduo epoch of late Eocene is the main time for hydrocarbon migration in south terrace of Gaoyou sag. On the basis of the analysis of fault activity intensity and regularity, its effect on controlling the hydrocarbon accumulation is studied. The results show that many active faults existed in early Sanduo epoch, and the single fault activity was in high intensity in late Sanduo epoch. Both the major fault and the sub-fault became the passages for longitudinal hydrocarbon migration. In the south terrace, the Sanduo fault activity intensity in its west was higher than that in its east. Such a difference of fault activity controlled the distribution of petroleum reservoirs in this area.The fault activity intensity in westward is larger than it in eastward, and the difference of the distributions of oil-gas reservoirs is determined by fault activity intensity.

Key words: Gaoyou sag, fault throw, petroleum transportation, reservoir