Reconstructed and Traced Pathways of Hydrocarbon Migration in Nanpu Depression,Bohai Bay Basin

The pathways of hydrocarbon migration in main hydrocarbon accumulation periods of Nanpu Depression in Bohai Bay Basin were reconstructed by the technology of streamline simulation.Based on the data of nitrogen compounds and maturity in crude oil,the traced pathways of hydrocarbon migration in the typical enrichment areas are studied.Streamline simulation results show that to reservoir inside and under source rock in south sags,there was a smaller scale hydrocarbon migration in late Dongying Formation(24.6 Ma ago),and a mass hydrocarbon migration in middle Minghuazhen Formation(9 Ma ago).To reservoir upper source rock in south sags and reservoir inside source rock in north sag,there was a small amount of hydrocarbon migration in middle Minghuazhen Formation,mass hydrocarbon migration in late Minghuazhen Formation(2 Ma ago).At present,hydrocarbon distribution in south sags does not match the simulation results,which indicates greater potential for exploration.The geochemical index of crude oil show that in the enrichment area of reservoir upper source rock,hydrocarbon migration was along faults strike,to the tectonic high position and sandstone on both sides of fault plane when the source fault stretched into the Sag center.For source faults parallel to the Sag center,hydrocarbon migration was along the faults tendency to the tectonic high position.In the enrichment area of reservoir inside source rock,hydrocarbon migration was along sandstone to the tectonic high position.