Meso-cenozoic Fault Evolution Mechanism In Yancheng Sag,Subei Basin

The formation and evolution history of Meso-cenozoic in Subei Basin is complex,and the fault system is well developed.Yancheng Sag is a typical representative of this basin.From the perspective of known hydrocarbon reservoir types in the sag,it is basically related to faults.In order to study the formation and evolution law of fault system in Yancheng Sag and the control effect of tectonic evolution on oil and gas accumulation,this thesis makes comprehensive use of seismic,well logging and geological data to carry out a detailed three-dimensional structural analysis of Nanyang sub-depression in Yancheng Sag.The geometric characteristics and kinematic characteristics of boundary fault zone,salt fault zone and some complex fault zones are studied,the fault activity time is determined,the fault evolution process is restored,sand box physical simulation experiment is designed for salt fault deformation mechanism,and finally the coupling relationship between tectonic evolution and hydrocarbon accumulation is analyzed.Combined with the two-dimensional seismic data of the whole area,the three-dimensional research results are applied to the whole Yancheng depression.The research results of this thesis are as follows:（1）Based on seismic and well logging data in the study area,the formation,thickness and sedimentary facies characteristics of Yancheng sag are analyzed,and the formation and evolution of Yancheng sag are divided into three stages:Taizhou-Funing depression stage（K₂t-E₁f）,Dainan fault depression stage（E₂d）and Sanduan-Yancheng depression stage（E₂s-Ny）.（2）The occurrence of Yan（2）faults from west to east presents the characteristics of"reverse fault→near-vertical fault→normal fault".Combined with the thickness characteristics and sedimentary facies in the interior of the sag,the strike-slip nature of Yan（2）faults is analyzed.The physical simulation experiments are designed according to the activity characteristics of Yan（2）faults,and it is clear that compressional and torsional action controls the formation and evolution of Yan（2）faults and its adjacent faults.（3）On the basis of defining the tectonic evolution background of the study area,the differences in the spatial and temporal distribution of oil and gas are analyzed,and the palaeotectonic map is used to analyze the folding deformation law of each stage,and the control effect of fault evolution on related oil and gas traps is clarified.