The Origin,Migration And Accumulation Of Oil In No.4 And Liunan Tectonic Belt Of Nanpu Sag

After more than 50 years of exploration in the Nanpu sag,the oil and gas resources are abundant.But in the No.4 tectonic belt and Liunan tectonic belt,the origin,distribution,migration pathway and accumulation period of oil and gas is not clear.In this paper,we will take the source rocks,crude oil as research objects,using the organic geochemistry analysis methods and biomarkers,combining with the comprehensive geological information to make a further analysis on oil and gass origin in No.4 and Liunan tectonic belt.According to the structural evolution of the study area,combined with the typical oil and gas reservoir,the distribution of oil and gas is clear.By analysising the fault feature and sand feature,combined with the crude oil properties and biomarkers of maturity parameters,put forward the migration pathway and direction in No.4 and Liunan tectonic belt.By analysising the burial history,thermal evolution history and fluid inclusions datas,define the oil and gas accumulation period.The oil and source correlation results show that the No.4 tectonic belt crude oil is mainly derived from Es1 and Ed3 source rock of Caofeidian subsag.The Liunan tectonic belt crude oil is mainly derived from Ed3 source rock of Liunan subsag.By studying the typical oil and gas reservoirs,it is concluded that the oil and gas of No.4 tectonic belt and Liunan tectonic belt are mainly distributed near the fault.The oil and gas are mainly in the Shallow stratum in No.4 tectonic belt and Liunan tectonic belt,and there are some oil distribution in the middle-deep stratum in No.4 tectonic belt.By analysising the different factors of the transport system,know that oil source fault play a key role on hydrocarbon reservoirs.Based on the oil molecule tracer,it is showed that fault is an important point of oil and gas in the vertical migration.The paper shows that oil and gas of Ed2 and Es1 injected since the ending sedimentary of Nm formation in No.4 tectonic belt.Oil and gas of Nm and Ng injected since the ending sedimentary of Nm formation in Liunan tectonic belt.The accumulation model of oil and gas in Es1 is “self generating and self storing”,in the layer of Ed2,Ng and Nm the accumulation model is “bottom generating and top storing”.