大挠度钻柱强度分析的平衡微分方程法

Method of Equilibrium Differential Equation for Analysis of Strength of Large Deflection Drill String

对小井眼、大曲率井中钻柱强度问题 ,以井轴为基准轴 ,在对井轴弯挠描述和钻柱微段三维受力变形分析的基础上 ,建立大位移钻柱平衡微分方程 ,采用Longe_Kutta法解之求内力 ,并依此求应力和建立强度条件· 对H767侧钻水平井施工中钻柱应力计算分析 ,结果说明与有限元模型和弹性化软绳模型比较相吻合 ,该模型比有限元模型计算简捷方便 ;比弹性化软绳模型更完善可信 ;该井钻柱破坏事故愿因在于井眼曲率过大 ,兼有应力集中·

To counter the strength problem of drill string in well of large curvature and small diameter, well axis was taken as datum axis. Based on description of deflection of well axis and on analysis of three dimensional forces of a small section of drill string, equilibrium differential equations of large deflection drill string were established. The internal forces were found by Longe_Kutta method. The stresses were found by using them and the strength prerequisite was established. Stresses of drill string in lateral horizontal well H767 were computed. The results are in agreement with those of finite element model and soft_rope rigidified model. But the method is simpler for computation than finite element model and is more perfect than soft_rope rigidified model. Curvature of the well is too large and there is stress concentration so that the fraction accident of drill string occurs.