动态载荷作用下UGS管柱非线性屈曲特性研究

为探究动态载荷作用下地下储气库(UGS)受压段管柱非线性屈曲特性,根据储气库井筒结构特点,建立了柔性约束下UGS管柱非线性屈曲力学模型,采用慢动力法阶跃式施加管柱外载荷,并结合考虑接触的管柱屈曲动力学方程,分析了动态载荷作用下管柱的非线性屈曲特性。以UGS-ZY11井现场数据为例,通过ABAQUS模拟计算进行对比研究,并分析储库产量和管径等因素对管柱非线性屈曲的影响,从而获得动态载荷作用下管柱屈曲演变过程和套管接触压力分布特点。研究结果表明:对于同一生产条件,动态载荷作用下管柱中和点到封隔器处的管柱处于连续非均匀的屈曲状态;管柱受力变形初始阶段,环空压力对其与套管壁接触存在“软约束”;随着储库产量和管径的增加,管柱屈曲变形过渡时间越短,管柱越容易发生螺旋变形;动态载荷作用下诱发管柱振动,导致径向位移较小的油管柱与套管壁发生接触,将加剧油套管损伤失效破坏,在管柱安全生产设计和运行时应做出相应的安全措施。研究结果为深入开展动态载荷作用下UGS管柱非线性屈曲特性研究提供了一种新的思路和方法。

Study on Nonlinear Buckling Characteristics of UGS String under Dynamic Loads

In order to explore the nonlinear buckling characteristics of the string in pressure bearing interval of underground gas storage (UGS) under dynamic loads, based on the structural characteristics of the gas storage wellbore, a nonlinear buckling mechanical model of UGS string under flexible constraints was built. The slow dynamic method was used to apply external load on the string step by step. Combined with the contact-considered string buckling dynamical equation, the nonlinear buckling characteristics of string under dynamic loads were analyzed. Then, taking the field data of well UGS-ZY11 for example, by means of ABAQUS simulation calculation, the influence of the factors like UGS production and pipe diameter on the nonlinear buckling of the string was analyzed, and the evolution process of string buckling and the distribution characteristics of casing contact pressure under dynamic loads were obtained accordingly. The research results show that for the same production condition, the calculation results of the slow dynamic method and the simulation results prove that under dynamic loads, the string from the neutral point of the string to the packer is in a continuous and non-uniform buckling state;in the initial stage of force deformation of the string, the annular pressure has a “soft constraint” on its contact with the casing wall;as the UGS production and the pipe diameter increase, the shorter the transition time of buckling deformation of the string, the easier the helical buckling deformation occurs in the string;under the action of dynamic load, the vibration of the string is induced, resulting in the contact of the tubing string with small radial displacement and the casing wall, which will aggravate the damage and failure of the tubing and casing, and corresponding safety measures should be taken in the safe production design and operation of the string. The research results provide a new idea and method for further studying the nonlinear buckling characteristics of UGS string under dynamic loads.