轴力及重力作用下钻杆最大弯曲应力计算

在考虑了钻杆接头、轴向力、钻杆重量以及钻杆本体与井壁接触等因素的前提下 ,应用平面弹性梁理论建立了钻杆在轴向拉力、轴向压力和轴向力为零时钻杆的最大弯曲应力计算模型。运用该模型计算出的钻杆最大弯曲应力远大于按井眼曲率计算的弯曲应力 ,这说明钻杆接头对钻杆弯曲应力的分布有较大的影响。在计算钻柱强度时 ,应考虑接头对钻杆弯曲应力的影响 ,以实现安全钻井。

CALCULATION OF MAXIMUM BENDING STRESS IN DRILLING ROD UNDER ACTION OF AXIAL LOAD AND PIPE WEIGHT

Based on the planar beam theory, the models for calculating the maximum bending stress of drilling rod under axial tensile load, compressive load, and zero load are given, in consideration of the effects of tool joint, axial force, drilling rod weight, and attachment of drilling rod with the wall of wellbore on bending stress of drilling rod. The results of calculation using those models show that the maximum bending stress in the drilling rod is much larger than that calculated using the method of assuming the drilling rod bending with wellbore curvature. The effect of tool joint must be considered in analysis of drillstring strength to reduce drillstring failure and keep safety in drilling process.