基于显式动力学的双封隔器管柱下入仿真建模与影响因素分析OA

To investigate the mechanical characteristics of multi-packer strings running through the curved sections of horizontal wells,a planar geometric model and an explicit dynamics simulation model for dual-packer strings were established.First,based on beam bending theory,the deflection curve equation and bending deformation energy formula for the packer string were derived.The critical contact criterion between the string and casing inner wall,as well as the calculation formula for critical buckling load,were determined.Additionally,a triaxial stress system was introduced for statics evaluation.Secondly,the dynamic strength variation patterns during the running-in process of a double packer string were simulated using explicit dynamics methods under different conditions of casing curvature radius,casing wall thickness,and packer spacing.The research demonstrates that:(1)Statics analysis shows that the triaxial stress intensity of the string meets the operational requirements under normal operating conditions,and the critical buckling load gradually decreases at an accelerating rate with the increase of the packer spacing.(2)The dynamics analysis shows that the stress of the packer string increases sharply after contact with the casing,and the maximum equivalent stress at a running-in velocity of 10 m/s reaches 655.4 MPa,mainly concentrated at the lower end of the tubing and the contact area between the tubing and rubber cylinder.(3)When the running-in velocity is 5 m/s,the contact pattern between the dual-packer string with a smaller spacing and the casing in the curved hole section changes significantly.For spacings ranging from 8 to 50 m,the maximum equivalent stress gradually increases with greater running-in depth.Overall,as the spacing increases,the maximum equivalent stress first increases and then decreases somewhat,but the time required for the maximum stress to stabilize becomes shorter.In the early stage of running in,the initial maximum equivalent stress of the packer string increases as the radius of curvature decreases.The maximum equivalent stress rises rapidly at a well inclination of 30° or so.When the radius of curvature is 200 m and 300 m,the maximum equivalent stress reaches 680.4 MPa and 702.3 MPa,respectively.Regarding local variations in casing wall thickness,a larger overall wall thickness leads to a larger maximum equivalent stress,and the amplitude of fluctuation increases as the tubing-casing annular clearance decreases.The research results provide a certain basis for the feasibility analysis of running the dual-packer string through the curved hole section,and lay a theoretical foundation for further in-depth dynamic simulation of the dual-packer string deployment.