中短半径水平井造斜率与螺杆钻具应力研究

应用非线性有限元法，建立了中短半径水平井螺杆钻具力学模型。分析了不同井眼曲率和不同弯角下120 mm大角度单弯螺杆钻具组合应力分布情况，最大等效应力随着曲率的增加先减小后增大，随着弯角的增大而增大；采用平衡曲率法，对大角度单弯螺杆造斜率进行了计算。确定了螺杆钻具组合极限应力与造斜率的关系， 等效应力线与分界线交点的左侧随井眼曲率增加而减小、等效应力线与分界线交点的右侧随井眼曲率增加而增加。该项研究为中短半径水平井大角度单弯螺杆钻具的安全使用、轨迹控制设及螺杆钻具的改进提供了依据。

Bulit-up Rate and PDM's Stress Analysis for Medium-and Short-radius Horizontal Wells

Based on the nonlinear FEM, a mechanical model for PDM used in medium and short radius horizontal well drilling is established in this paper. With this model, stress distribution on 120 mm single bending high angle PDM is determined under different borehole curvatures and different bend angles. The maximum equivalent stress will decrease earlier and increases later when the borehole curvature increases, and will increase with the bend angle. Based on the method of equilibrium curvature, built up rate of high angle single bend PDM is calculated. By the analysis of limit stress vs. built up rate, it is concluded that equivalent stress decreases with the increase of borehole curvature on the left side of the cross point of equivalent stress line and the boundary and contrarily on the right. This study is significant for the safe operation of high angle single bent PDM, the design of trajectory control as well as the improvement of PDM.