水平井段钻杆接头的力学效应

Mechanical effects of drillstring joints in horizontal holes

通常在研究水平井段钻柱受力和变形时，忽略钻杆接头的影响，仅将钻柱当作光滑管柱处理，因此计算结果不够准确。实例计算时分析了接头对变形过程、屈曲临界力和弯曲应力的影响，提出了计算正弦屈曲临界力的新方法。分析指出，当接头外径较小时，外径的变化将改变正弦屈曲临界力。接头外径增大会不断增加螺旋屈曲临界力，因而具有抑制螺旋屈曲的作用。接头外径大到一定程度，就不再影响正弦屈曲临界力。当轴向压力较小时，接头引起钻柱弯曲应力；当轴向压力较大时，考虑接头影响不会引起屈曲钻柱弯曲应力计算值的增加。

In studying the force and deformation of drillstring in a horizontal hole, the drillstring is considered as a smooth pipe, therefore the influence of the drillstring joints is usually neglected, and this will result in the inaccuracy of the calculation. By means of an example of calculation, the influence of the joint on the drill pipe deformation, critical buckling load and bending stress is analyzed, and a new method for determining the sin critical buckling load is presented.Analysis shows that,when the outside diameter of the joint is small, the variation of the outside diameter will change the sin critical buckling load. The increase of the outside diameter of the joint will result in the increase of the critical spiral buckling load, thereby the spiral buckling can be restricted. When its outside diameter is laoger than a given value, the joint has no influence on the sin critical buckling load. When the axial load is small, the joint produces the flexural stress; when the axial load is large, considering the influence of the joint will not result in the increase of the calculating value of the flexural stress of the buckling drillstring.