Evolution Of Tectonic Stress Field And Fault Response Characteristics In Dongying Sag

The Dongying Sag is a hydrocarbon-rich sag in the southeastern part of the Jijiyang depression in the Cenozoic rift basin of the Bohai Bay.The study of tectonic stress field and fault formation mechanism and distribution law is of great significance for the deep exploration and development of sag oil and gas.Based on the 3D seismic data of Dongying Sag and the research results of regional tectonic setting and tectonic stress field evolution in the Bohai Bay Basin,this paper applies generalized fault theory to constructive analysis of key structural units and structural features in the depression.The regional unconformity interface characteristics and structural deformation research results are divided into tectonic evolution stages.On this basis,the stress system and its evolution process in different tectonic evolution stages are analyzed,and the fault response characteristics of Dongying Sag and the settlement and deposition are analyzed.The control role and further analysis of the relationship between the tectonic stress field evolution of the Dongying Sag and the evolution of the Bohai Bay Basin.On this basis,the two-dimensional and three-dimensional structural physics simulation experiments are carried out to simulate the effect of the early-formed pre-existing faults on the formation of late faults in the Dongying sag during the Oligocene period,and the actual seismic profiles and The plane features are compared to propose a more reasonable sag evolution mechanism and interpretation.The paper has obtained the following understandings:?1?The transition time of the tectonic stress field in the Dongying sag is consistent with the Bohai Bay Basin:the rifting effect caused by stretching in the northwest-south direction about 40 Ma?E2s3deposition?;near north and south after 40 Ma the effect of the sag,the depression and the sag of the extension;?2?the first rifting depression in the northwest-south direction is the tectonic pattern of the?northwestern fault of the northwestern?,and the stress system is transformed into the north-south extension.The change of basin pattern leads to the deviation of tectonic subsidence,which forms the basin structure of?Northern Fault South?,and the paleo-structural geomorphology environment has undergone great changes.?3?The formation and evolution of the central fault zone of Dongying Sag is mainly affected by the northern steep slope zone.The control of the Nanhe Shengyong fault zone is generally a collapsed structure,which is the most complex zone of the superimposed deformation of the Dongying sag;?4?depressions have had two tectonic calming effects since the middle of the Eocene,one time above the T₄interface.During the sedimentary period of the second sedimentation,one occurred in the depression period above the T₁ interface and continued to this day;?5?the formation and evolution of the Dongying sag is affected by the deep structure of the lithosphere Joint control of structural evolution of its region.