The study is based on the analysis of characters of hydrocarbon migration within a lower source rock-upper reservoir combination

and 3D seismic and logging data.We worked out a method to determine the preferential pathways for hydrocarbon migration through combining fault activity ratio with hydrocarbon potential energy on fault plane and combining net-to-gross ratio with fluid potential on top of sand bodies.It can be used to define the scope of preferential hydrocarbon accumulation in this mode.Its application in the 1

st

member of Nantun Formation (K

1

n

1

) within a local structure of Bei’er Sag

Hailar Basin

reveals that hydrocarbon migration in the reservoir could be divided into two modes:the mode of vertical migration and the mode of vertical migration followed by lateral migration.There are 17 preferential migration pathways for the former and 11 for the latter.Correspondingly

their scopes of preferential hydrocarbon accumulation are within 2.3 km and 1km respectively

just coinciding with the practical hydrocarbon distribution.It demonstrates that this method is feasible for determining preferential pathways in hydrocarbon migration within a lower source rock-upper reservoir combination

and conducive to delineating the scope of petroliferous region in the reservoir.In conclusion

it is of importance to guide future petroleum exploration.