Conditions Of Formation And Primary Controlling Factors Of Petroleum Reservoirs In The Damintun Depression

Corresponding to the worldwide petroleum exploration period,research on petroleum reservoir formation is attached more importance to.Based on the structural and sedimentary evolution of basin,according to the static elements such as source rock,reservoir,cap rock, carrier systems,traps,et al.,these processes such as petroleum generation,migration and accumulation are mainly discussed,reservoir-forming models are built,primary controlling factors and formation regularity of petroleum reservoir are analyzed,and favorable areas are put forward.Dmintun Depression is a typical terristrial half-graben in Eastern China whose Palaeogene area is about 800km~2.After about 40 years’ exploration,Damintun Depression has been maturely and intensively explored,and has such features as rich petroleum resource, complex types of petroleum reservoir and high degree of exploration.Up to now,reserves had been proved in the Archaeozoic and Poterozoic buried hills,and sandstones of the Third Member of Shahejie Formation,and the proved reserves is about 3.0889×10~8t,mainly at the positive structures.In recent years,some wells drilled at lower buried hills of basement and turbidite sandstones of the Fourth Member of Shahejie Formation found commercial hydrocarbon,which proved that Damintun Depression is still potential.Focused on petroleum reservoir,with the drilling,cores,analysis and formation testing data,based on the description of basic elements,different source rocks are determined with the oil-source correlation,the high-wax oil was from oil shale and the normal oil was from lacustrine mudstone.The migration directions are estimated with the changes of physical property,maturity parameters and nitrogen-containing compounds,the charge time is judged from fluid inclusion and K/Ar isotopic dating of authigenic illites in diagenetic minerals.It is concluded that the Anfutun Sag charged high-wax oil for the West Slope towards the west and south,and for the Jinganpu Structural zone towards the east,the Shengdong Sag charged high-wax oil for the Dongshengpu and Jinganpu Structural zone towards the north,and the Rongshengpu Sag charged normal oil for the Qianjin,Fahaniu Structural zone and area south to the Dongshengpu buried-hill separately towards the west,east and north.Combined with the formation,types and distribution of different traps,this article analyzes the carrier systems,builds reservoir-forming models and interprets the types and distribution of carrier systems in different structurai zones.Then based on the types and distribution of the proved reservoirs,we discuss the carrier systems controlled the distribution and types of the petroleum reservoir,point out that the carrier systems affected the types and distribution of different traps,controlled the lateral and vertical distribution of petroleum reservoir. Combined with simulation of the typical profiles,we draw the conclusion that the carrier systems controlled dynamically the formation and distribution of petroleum reservoir at different stages and put forward further potential explorative areas,which can guide and be used for reference in other rift basins in Eastern China.