Tectonic Evolution And Numerical Simulation Of Xuxi Fault Zone In Songliao Basin

Xuxi fault zone is a sag boundary fault in the western margin of Xujiaweizi fault depression.Xujiaweizi fault depression has a good prospect for natural gas exploration.However,the structural characteristics and evolution process of Xuxi fault zone are complex,and the understanding of its structural evolution law and genesis is still different,which restricts the exploration and research of deep natural gas in this fault depression.Based on geological and seismic data,combined with previous research results,the geometric characteristics of the Xuxi fault zone are analyzed,and the structural evolution process and genetic mechanism of the Xuxi fault zone are systematically analyzed by using balanced section technology.Finally,the discrete element numerical simulation method is used to simulate the tectonic evolution process of Xuxi fault zone,so as to verify the reliability of the previous theoretical analysis and determine the final genetic mechanism.Main findings:(1)Xuxi fault is a large normal fault formed under the action of extension stress,which together with Xuzhong fault controls the formation and evolution of Xujiaweizi fault depression.(2)The tectonic evolution of Xuxi fault zone can be roughly divided into six periods,which are huoshiling Stage,Shahezi stage,Yingcheng stage,denglouku Formation-Quantou Formation early sedimentary stage,upper Quantou Formation-Qingshankou Formation sedimentary stage and Nenjiang Formation-Quaternary sedimentary stage.The Xuxi fault zone in Huoshiling and Shahezi periods was in the tensile stress environment and experienced from the initial formation to the maximum activity intensity.During the sedimentary period of the first member of Ying formation,Xuxi fault was atrophic and subjected to the NW-SE tensile stress,while in the end of the first member of Ying Formation,it was subjected to the NE-SW compressive stress.During the sedimentary period of the 3rd Member of Ying Formation,the Xuxi fault zone was in the stress environment of NW-SE extension,and the fault-controlled depression was weakened.At the end of the 3rd member of Ying Formation,the local area suffered denudation due to the action of regional compressive stress.(3)By means of discrete element numerical simulation,the corresponding tensile and compressive stresses are applied to the boundary of the model in each period to realize the deformation process of the simulated stratum.The simulation results are basically consistent with the structural deformation characteristics of the above period,which is a good verification of the theoretical analysis.Therefore,it is confirmed that the tectonic evolution of xuxi fault zone is the result of the superimposition of multi-stage extension and compression deformation.