考虑初弯曲时水平井眼中杆柱的稳定性

利用能量法研究了水平并眼中杆柱的稳定性，推导出水平并眼中具有初弯曲的杆柱稳定性轴向临界压力的计算公式，讨论了失稳变形曲线正弦半波数的确定方法，分析了初弯曲对轴向临界压力的影响。计算实例分析表明，轴向临界压力从r随初弯曲最大挠度a0的增大而减小，当a0较小时，Pcr减小幅度不大；当a0较大时，Pcr的减小较大。认为在分析杆柱的稳定性时，若初弯曲较大，就不能把杆柱当作直梁来处理，必须考虑初弯曲的影响。

Stability of drill stem with initial deflection in horizontal wells

The stability of drill stem in horizontal wells is investigated by the energy method. The equation for calculating theaxial critical buckling force of the drill stem with initial deflection in horizontal wells is derived, the method for determin-ing the number of half-sine wave of the deflection curve is discussed, and the influence of the initial deflection on axialcritical buckling folce is analyzed. An example of calculation shows that, the axial critical buckling force per decreaseswith the increase of the maximum initial deflection ao, when ao is small' Per decreases in a small degree; while ao islarge' Per decreases in a considerable degree. It is indicated that, in analyzing the stability of the drill stem, the influ-ence of the initial deflection of the drill stem should be taken into consideration if the deflection is large.