Fault activity features of Baxian Sag in Paleogene in Jizhong Depression

Based on previous research results,and the previous research results,the fault activity characteristics of Baxian Sag in Paleogene is studied according to seismic and geologic data using fault throw method. The results show that there mainly exist NE faults in the studied area and the studied area presents a half-graben form because of the control effect of Niudong fault. There are different geometrical morphologies of fractures: on the plane,the fractures are mainly parallel and obliquely intersecting; on the profile,they present are Y-type,double Y-type,graben type and horst type. The faults present the features of multi-stage activity. There are mainly three stages: in Kongdian-Sha-4 stage,there are a small number of active faults,but their activity is strong; in Sha-3-Sha-2 stage,the number of active faults increases,a large number of three-level and four-level faults are developed,but their scale is small and their activity is weak; in Sha-1-Dongying stage,the activity of the faults became stronger,and to late Dongying stage,the fault activity trended stable. In Paleogene,the activity of the faults became strong from south to north,and the direction of the faults gradually changed from NNE to NEE. In Baxian Sag,the Sha-3-Sha-2 stage is the most favorable to hydrocarbon accumulation,and the Sha-1-Dongying stage is secondary; the active fractures provide migration pathways for buried hill hydrocarbon.