斜直井内钻柱的非线性螺旋屈曲

基于最小位能原理,研究了斜直井内钻柱的非线性螺旋屈曲问题。利用圆柱面坐标系,使接触非线性问题简化成了纯几何非线性问题。对于上端周向自由,下端铰支的钻柱,用Rayleigh-Ritz法得到了有一定横向载荷作用时,确定螺旋屈曲临界载荷无量纲形式的非线性积分方程。应用符号运算软件Maple10,对具体的工程算例进行了求解。研究发现:该文的计算结果与已有的实验结果吻合,说明钻柱的螺旋屈曲问题是非线性问题,同时也证实了该文的非线性算法的有效性。该方法可用于求解斜直井内的钻柱屈曲问题。

NONLINEAR HELICAL BUCKLING OF DRILLSTRING IN INCLINED WELLBORE

Based on the principle of minimum potential energy, the helical buckling of a drillstring is studied, with its top end free circumferentially and lower end hinged. To simplify the problem from contact nonlinear to geometric nonlinear, cylindrical coordinate system is used in the derivations. Using Rayleigh-Ritz method, the non-dimensional nonlinear integral equations are developed for determining the helical buckling loads corresponding to a certain lateral load. Practical examples are analyzed with the help of symbolic computational software Maple 10. It is found that the numerical results agree with existing experimental data. It implies that the helical buckling of a drillstring is a nonlinear problem and the established nonlinear analytical method may be used for analysis of drillstrings in inclined wellbores.