In order to study the distribution law of hydrocarbons controlled by faults in the lower source and upper reservoir type of petroliferous basins, a set of determination methods for the conversion period from fault transport to obstruction oil and gas was established. The method was derived based on (i) the study of the conversion period from fault transport to obstruction oil and gas, (ii) its relationship with hydrocarbon migration and accumulation, and (iii) by determining the relationship between the displacement pressure of fault filler in the caprock and that of reservoir rock under the caprock with time, and considering the period when the two were equal. The new method was then used to determine the conversion period from transport to obstruction oil and gas of the F5 fault in the 2nd member of the Dongying Formation in the Laoyemiao structure of the Nanpu Sag, Bohai Bay Basin. The results show that the conversion period from transport to obstruction oil and gas of the F5 fault in the 2nd member of the Dongying Formation is earlier than the period of massive hydrocarbon expulsion from the source rocks of the 3rd member of the Shahejie Formation and the 1st member of the Shahejie Formation at the late period of sedimentation of the 1st member of the Dongying Formation. This is not conducive to the migration and accumulation of oil and gas generated from the source rocks of the 3rd member of the Shahejie Formation and the 1st member of the Shahejie Formation in the 2nd member of the Dongying Formation. In the late period of sedimentation of the lower member of the Minghuazhen Formation, the oil and gas transport period of the F5 fault is later than the period of massive hydrocarbon expulsion from the source rocks of the 3rd member of the Shahejie Formation and the 1st member of the Shahejie Formation, and it has not been converted to the period of sealing oil and gas so far. This is even more unfavorable for the migration and accumulation of oil and gas generated from the source rocks of the 3rd member of the Shahejie Formation and the 1st member of the Shahejie Formation in the 2nd member of the Dongying Formation. The results are coincident with the fact that the oil and gas in the 2nd member of the Dongying Formation of the Laoyemiao structure has only been found in the high part of the structure, but not in the low part of the structure. It suggests that the method is feasible to be applied in determining the conversion period from fault transport to obstruction oil and gas.