基于有限元分析的直井中钻柱螺旋屈曲临界载荷定义

采用有限元法对直井中钻柱非线性屈曲控制微分方程进行了求解,力学模型中考虑了钻柱的重力,摒弃了传统分析中的无重力、等螺距和小位移假设,考察了不同边界条件对钻柱屈曲的影响。基于有限元分析的结果给出了钻柱非线性螺旋屈曲临界载荷定义,分析了位移高阶项在钻柱弯矩计算中的影响。分析表明,根据给出的定义确定的钻柱螺旋屈曲临界载荷与实验数据吻合,位移高阶项在弯矩计算中不可忽略。为石油钻采工程中钻柱螺旋屈曲临界载荷的预测提供了一种有效的方法。

THE DEFINITION OF HELICAL BUCKLING CRITICAL LOAD OF TUBING IN STRAIGHT WELLS BASED ON THE FINITE ELEMENT ANALYSIS

The nonlinear governing differential equilibrium equations of tubing buckling in straight wells are solved by the finite element method.The effect of tubing gravity is included.The assumptions of no gravity,constant pitch,and small displacement in traditional analysis are abandoned.The effects of different boundary conditions on the buckling of tubing are studied.The definition of helical buckling critical load of tubing in straight wells is given based on the finite element analysis.The influence of high order derivative of displacement on the value of drill tubing bending moment is studied.It is shown that the helical buckling critical load of tubing based on the theory presented in this paper fits well with the experiment result,and the high order derivative of displacement in the equation of tubing bending moment can not be neglected.An efficient method to predict the helical buckling critical load of tubing in straight wells of petroleum engineering is presented.