Buckling Analysis And Preventive Measures Of Injection Pipe Strings In Gas Storage Wells

The injection production string of gas storage will be affected by self weight,temperature and internal and external pressure in the process of operation,and when the injection production string is constrained by casing,the injection production string will produce buckling deformation,which will experience the transition process from plane single point contact to space spiral contact,and the buckling behavior is very complex.In order to avoid and reduce the buckling of the injection production string,the finite element analysis method is adopted in this paper.The injection production string is divided into beam element,and the multi-directional contact gap element and beam element are combined to establish the geometric and contact nonlinear finite element model in the wellbore.By using the dynamic relaxation method,the six buckling configurations before one pitch and the buckling configurations of multiple pitches are obtained,and the shear force,bending moment and contact force of various buckling configurations are analyzed.The dimensionless method is used to obtain the dimensionless critical compression loads of various buckling configurations,which improves the calculation efficiency.Through the study of injection production string of gas storage with different dimensionless length,it is concluded that with the increase of pressure load,the position of contact point is gradually stable from the initial unstable state to the final stable state.With the increase of length,the critical compression load of various configurations decreases gradually.Near the bottom of the well,the shear force,bending moment and contact force are all maximum.With the increase of length,the values of shear force,bending moment and contact force decrease in turn.At the wellhead and bottom of the well,the values of shear force and bending moment are larger.The dynamic relaxation method is used to obtain the spiral buckling deformation curves of 1 to 15 pitches and the dimensionless axial compression load of each pitch.Through the function of the axial compression load and the number of pitches,the curve is polynomial fitted,and the fitting formula of the relationship between the critical load and the pitch is obtained.In the study of compression section,with the increase of compression load,the position of contact point gradually moves down until it is basically unchanged.With the increase of pressure load,the critical length of injection production string decreases gradually.According to the calculation of the influence of the compression load on the critical length,the fitting formulas of the dimensionless length and the dimensionless load of various buckling configurations are obtained,which is of guiding significance for the placement spacing of the centralizer of the injection production string and the buckling discrimination of the injection production string in operation.