Tectonic Evolution And Its Control On Hydrocarbon Accumulation,Dongying Sag

Dongying Sag is a typical half graben basin,developed in the hanging wall of Binnan-Chennan-Qingxi Fault,located in the southeastern part of Jiyang Depression,Bohai Bay Basin.Based on high accuracy 3D seismic data interpretation,combined with of regional geological background and drilling data in Dongying area,using the fault-bend-fold theory and boundary faults growth model,this paper analyze s unconformities,geometry characteristics of boundary faults,division of tectonic stratigraphy etc..As well as fault plane growth histories,in order to study the characteristics of the tectonic evolution and its control on oil and gas accumulation by tectonic evolution,Dongying Sag.The conclusions are as follows:1.Based on the stratigraphic and structural characteristics in seismic and drilling data,determine the mainly four major regional unconformities in Dongying Sag:Mz bottom,Ek bottom,Es3x bottom and Ng bottom.There are five tectonic-stratigraphic sequence:basement tectonic layer,Paleozoic tectonic layer,Mesozoic tectonic layer,Paleogene tectonic layer,Neogene-Quaternary tectonic layer.2.Through the section,plane and 3D geometry analysisof boundary faults in Dongying sag,determine its boundary fault of Dongying Sag is Binnan-Chennan-Qingxi fault,boundary faults of Boxing sag are Gaoqing-Pingnan fault and Shicun fault,the former two intersect at the detachment surface in the deep,while Shicun fault detaches in the shallow.Boundary faults of Dongying sag is obviously segmented and partitioned,and devided Dongying sag into four regions:West,Middle-West,Middle-East,and East region.3.Use the structure-thickness map to analyze growth of the boundary fault.The initial boundary faults were several independent small faults,and then merged into a chain,becoming a new normal fault:Chennan fault developed after Mesozoic,respectively merged with the Qingxi fault and Binnan fault in Es3s and Es2;Binnan fault developed since Es4,and Qingxi fault developed since Ek;Shicun fault mainly active in Ek-Es4,middle and northeast segments of Gaoqing fault independently active during Es3s-Es2,and merged the Es3s.4.Each segments of Dongying sag experienced evolution stages roughly the same,mainly Paleozoic pre-rift stage,Mesozoic extensional rift stage,denudation at the end of Cretaceous,Paleogene(Ek-Ed)fault development stage,post rift depression Neogene-Quaternary.Faults of different segments are of differences during evolution.Gaoqing-Pingnan fault was negative inversion at the end of the Cretaceous,east segment of Chennan fault and Qingxi fault was positive inversion in the end of deposition of Dongying formation.5.Dongying sag experienced strong tectonic activities,developing a lot of high-angle faults,unconformities,anticlines,stratigraphic overlap etc..Tectonic evolution controlled the types of trap,and distribution of traps type,and reservoirs and distribution of oil and gas.