Control and Transformation of Control-hill Faults in Rift Basins During the Development of Fault-controlled Buried Hills:A Case Study of the Gangxi Fault and the Gangbei Buried Hill in the Huanghua Depression
Fault-controlled buried hills is the main type of hydrocarbon-bearing structures,and research in this field has evolved from focusing on single weathered crust types to exploring multi-layered series within buried hill interiors.The control-hill fault,which defines the boundary of the buried hill,is a critical breakthrough point for studying this type of structure.Using the Gangxi Fault in the Huanghua Depression as a case study,this research explores the constraints imposed by mountain-controlling faults on buried hill development and the transformation of buried hill structures.We analyzed the geometric and kinematic characteristics of the moun-tain-controlling faults,as well as the macroscopic and internal structures and evolution of the Gangbei buried hill.The study reveals that the Gangxi Fault can be classified into three types:planar,listric,and slope-flat,which together form the macroscopic features of the boundary cliff surface.The movement rate of the Gangxi Fault during the Neogene was less than 20 m/Ma,while the average movement rate during the Oligocene and Paleogene was 100 m/Ma.In the Eocene,and the movement rate exceeded 200 m/Ma,with weaker fault ac-tivity in the southern section and stronger activity in the northern section along the strike.The Gongbei buried hill exhibits a macrostructure with higher elevation in the southern and lower elevation in the northern section.The evolution of the Gangbei buried hill consists of three stages:the inner stratum construction stage,the fault-controlled buried hill development stage,and the structural stabilization and subsidence stage.The geometry,kinematics,and evolution of the Gangxi Fault,as a control-hill fault in a continental rift basin,significantly im-pact the buried hill,primarily by controlling its formation process.It also affects the macro-morphology of the buried hill and the reconstruction of its internal structure,which in turn influences trap conditions,oil and gas migration,and reservoir performance.
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