Transport Systems And Migration-Accumulation Models Of Oil And Gas In Western North Margin Of Qaidam Basin

The western north margin of Qaidam Basin is rich in oil and gas,but the exploration is low.It is unclear about the transport systems,the distribution rules and controlling factors of oil and gas reservoirs in the entire region.Therefore,the composition of the transport grid in each region is analyzed,the transport elements are evaluated and the distribution characteristics of the transport elements,the transport performance and the combination style of transport are studied in this paper.Finally,on this basis,the study of the dynamic migration process of oil and gas in the study area is conducted from the perspective of structural evolution,combining the characteristics of oil and gas distribution in each zone,so as to analyze the hydrocarbon accumulation of transport systems in different structural zones.The western north margin of Qaidam Basin mainly develops four types of transport systems,including far-source fault-unconformity-sand interaction stepped type,inline type,far-source fault-sand vertical type and deep-source fault-sand vertical type.Pingtai area is dominated by far-source fault-unconformity-sand interaction stepped type.Lenghu third area is dominated by inline type.Deep layers in Lenghu fourth and fifth are dominated by far-source fault-sand vertical type while shallow layers are dominated by deep-source fault-sand vertical type.Lenghu sixth,seventh and Eboliang area are dominated by far-source fault-sand vertical type.The distribution of oil and gas is affected by the matching relationship between the formation and development time of traps in each structural zone and hydrocarbon generation and expulsion period of the source rocks.Areas that have a good matching relationship develop primary reservoirs.Deep faults play a constructive role,while shallow faults not only play a role in migration,but also destroy some previous primary reservoirs.The development degree of sandstone transport layer controls the hydrocarbon distribution in some areas.The connectivity and conduction performance of sandstones is poor in those areas where the development degree of sandstone transport layer is poor.So oil and gas is difficult to accumulate in those areas.