Fault Evolution And Analogue Modelling Of Gaoyou Sag In Subei Basin

Gaoyou sag,located in the south of Subei basin,is the most proved sag in Subei basin,and is a meso-cenozoic extensional superimposed basin.Its complex and unique structural characteristics have been the focus of many scholars.Based on the high-precision three-dimensional seismic interpretation,this paper systematically analyzed the fracture geometry and kinematic characteristics of Gaoyou sag,determined the period of fault activity,restored the fracture evolution process,and analyzed the stress mechanism of fracture formation.Meanwhile,physical simulation experiments were designed for the fracture deformation mechanism to reproduce the evolution process of Gaoyou sag.The study shows that the fault evolution in Gaoyou sag can be divided into three stages,namely Wubao stage,Dainan stage and Sanduo stage,corresponding to the first,second and third period of rifting respectively.Main boundary fault zhen(2)fault horizontal segment,controlling-depression fault hanliu fault is also a segment fault,long-term activity;In the sedimentary period of Funing formation,the same faulting period resulted in different faulting characteristics due to different extension modes in different regions.In the sedimentary period of the Dainan formation,boundary faults zhen(2)and controlling-depression hanliu fault developed distinctive high-angle fault steps in the footwall.The stress field of Gaoyou sag in the late sedimentary period of Sanduo formation changed direction and part of east-west strike faults were formed under the stress field of north-south extension.At the same time,according to the characteristics of fault activities in different periods,analogue modellings were set up for different periods,and a large number of antithetic faults were successfully simulated in the east of Gaoyou sag of first period of rifting,and "V"-shaped anticlinal fault combinations were formed in the west.In the second period of rifting,two controlling-depression faults were alternately controlling-depression,which simulated the structural characteristics of the fault-depression.The stress field of third period of rifting shifted,and the pre-existing faults formed by first and second period of rifting maintained the original fault trend in the third period of rifting,and the new east-west trending faults were formed in the area free from the constraint of the pre-existing faults.