Numerical Analysis And Model Establishment Of Dynamic Response Of Perforating String

There will be a large of shock waves generated during perforating operation,which would result in the occurrence of bending fracture of tubing string,the damage of packer,and the expansion of perforating gun,leading to the lower security of perforating operation.In order to reduce the occurrence of perforating accidents,the dynamic response of tubing string during impact loads were studied in this paper.Considering the effects of axial load,lateral load and torsional load,the dynamical model had been established based on vibration mechanics theory of cantilever beam,and the differential equations of longitudinal vibration were deduced.Applying transient dynamic analysis based on ANSYS software,the three-dimensional finite element model of string was established,the transient response of string were obtained under the components of axial,transverse and torsional loads respectively.Considering the influence of perforating fluid,the fluid dynamics model of perforating fluid were established based on FLUENT software,and the pressure pulsation of perforating fluid were obtained.Considering the pulsation pressure of perforating fluid as external load,the influence of perforating fluid to string dynamic response was analyzed.Considering the explosion impact load and the effect of perforating fluid pulsation pressure,the coupling model of perforating fluid and string was established,and the dynamic response of displacement,velocity,acceleration and equivalent stress of perforating string can be obtained.The transient dynamic response of perforating string was analyzed based on finite element method,the displacement,velocity,acceleration and equivalent stress of string are cyclical changes by time.And the more near the packer,the smaller the response amplitude,which indicate that the shock wave attenuate with the distance between string cross section and perforation explosion source.Along the axis direction of string,the displacement,velocity and acceleration decrease from the lower end of the string to the packer end,and the maximum equivalent stress increase gradually.There is stress concentration phenomenon at the top of string because of the constraint of packer,and the equivalent stress increase gradually from inner wall to outer wall.Applying the controlling variables method,which is used to analyze the influence of perforating string dynamic response considering the length,outside diameterand thickness of string.The amplitude of string dynamic response decrease with the increase of outer diameter and thickness of string,so the outer diameter and wall thickness should be larger.This paper can provide references for combination optimization and intensity security analysis of string under the impact loads.