Neogene-Quaternay faulting activities and their influence upon hydrocarbon accumulations in Bohai Bay Basin were analyzed based on hydrocarbon distribution characteristics and geological settings.It shows that the late faulting activity influenced the macroscopic distribution of the hydrocarbon accumulation assemblage and controlled the Neogene oil and gas enriched types and enriched belts of different depressions.Effect of faults different activity on hydrocarbon accumulation can be characterizedby fault activity difference coefficient(FDC).When the early and mid-generation and expulsion of hydrocarbon

the fault activity is strong and when late generation and expulsion of hydrocarbon the fault activity is weak

that is most favorable for hydrocarbon accumulation.Based on fault activity rate and FDC

we categorized the faults into Ⅰ

Ⅱ and Ⅲ kinds in terms of their controlling ability on oil and gas accumulation.The first two types with faster fault activity rate and larger FDCs

were distributed in places where oil and gas are highly enriched in the Neogene and the last type with slower fault activity rate and small FDC was in places where oil and gas enrichment is poor in the Neogene.Based on the understanding

we propose that differences in faulting activities controlled oil and gas accumulations and the types of faults determined the level of oil and gas enrichment.