侧钻钻柱三维二重非线性问题的研究

研究大曲率定向井、水平井的钻柱受力和变形问题，采用线性分析方法难以满足工程实际的要求。针对以上难题，利用有限元法研究了钻柱在井底的二重非线性（几何非线性和接触非线性）问题。提出了在三维井眼内，根据各测点的井深、相应测点处实测的方位角和井斜角来获得确保钻柱参考构形长度不变的井眼轴线插值方法。从而实现了由井眼轴线的曲率和挠率，计算得到复杂三维井眼中钻柱的初始内力。此方法为三维钻柱力学分析提供了一种新的研究思路，也对定向井、水平井等钻井工艺作业效率的提高、井下事故的减少有着重要的意义。

STUDY ON 3D DUPLEX NON LINEARITY OF CASING EXIT RE ENTRY DRILLING STRING

The mechanical analysis of the drill string used in high curvature directional wells and horizontal wells finds that the linear analysis method cannot meet the actual engineering requirements. Thus the finite element method is used to study the duplex nonlinearity (geometric nonlinearity and contact nonlinearity) of the drill string at the well bottom. A well axis interpolation method is suggested to use well depth, azimuth and inclination at different survey points to keep the length of the referenced drill string unchanged. The initial internal force of the drill string in 3D wells can thus be obtained from the curvature and the torsion of the well axis. This method has provided a new way for mechanical analysis of 3D drill string. And it is significant for operators to improve the efficiency of directional and horizontal well drilling and reduce the downhole accidents.