弯螺杆钻具力学特性分析与设计

设计或选择弯螺杆钻具组合时，既要确定弯螺杆钻具的总体方案结构参数，还要预测该钻具组合的造科能力。利用结构弯角的等效角和等效横向载荷，推导了用以分析具有结构弯角的螺杆钻具组合力学特性的三弯矩方程组，并应用它确定钻具组合的平衡曲率。根据实钻结果研究了弯螺杆钻具组合造斜能力与平衡曲率间的关系，得出了平衡曲率系数的数学表达式，并将其应用于φ39．7mm套管侧钻水平井的φ89mm弯螺杆钻具总体方案设计。计算表明，这种φ89弯螺杆钻具应设计成传动轴本体上带有稳定器的单弯钻具。

Analysis of mechanical characteristic of positive displacement motor with bent housing

In designing or selecting hottom hole assembly with bent screw drill, it is necessary to determine the structural pa rameters of the positive displacement motor(PDM) with bent housing and predict the build-up rate of the PDM. On the basis of the equivalent angles and equivalent cross loads, three moment equation sets for analyzing the mechanical charac teristic of the bottom assembly with the bent housing PDM are derived, and the equation sets are used to determine the equilibrium curvature of the assembly. The relatin between the build-up rate and equilibritum curvature of the bottom hole assembly with bent housing PDM is studied based on the drilling practice, thereby the mathematical expression for the equilibrium curvature coefficient is worked out, which is applied to guide the overall scheme design of φ89mm PDM used in φ139.7mm casing side tracked horizontal hole. Calculation shows that this PDM should be designed as single bent screw drill with stabilizer on the transmission shaft.