大位移井钻柱的动态分析

Dynamic analysis on drill string in large deflection well annulus

分析了大位移井旋转钻柱的受力变形特点及钻柱与井壁接触机理。根据动力学原理引入碰撞恢复系数并完善和简化了钻柱与井壁动态摩擦接触模型。采用有限元理论 ,将威尔逊θ法、牛顿拉裴逊法和放松约束试算法相结合 ,解决了大位移井钻柱动力学问题及钻柱动态接触边界待定问题。计算及分析结果表明 ,所建理论模型是合理的和简便的。在钻柱旋转过程中 ,碰撞或连续接触可能交替存在或并存 ,这与井眼条件和转速有关 ,对钻柱与井壁接触形式的任何假设都可能是误差产生的根源。动态响应均值的非线性效应与静态分析结果表明 ,一般井眼曲率大于 5°/( 30m)时 ,线性动态分析的误差不容忽视 ,转速较高 (大于 70r/min)时 ,须考虑动态因素的影响 。

The characters of force and deformation of drill string in a large deflection well and mechanism of contact of drill string with well wall in annulus and in spinning patterns were analyzed. According to the dynamic principles, a contact-restored factor was introduced, and the mathematical models for expressing the dynamic friction contact were further perfected and simplified. By using finite element theory, the dynamics problem of drill string in a large deflection well and the unknown dynamic contact boundary problem of the drill string were solved by combining Wilson- method with Newton-Laphson method and loosing constraint method. The computations show that the theoretical models are feasible, perfective and simple. In the rotation of drill string, impact or continuous contact may happen alternatively or simultaneously, which is related to the status of well bore and rotary speed. Any hypotheses for contact forms between drill string and well wall may be the origin of analysis error. Dynamic analysis must be done at a high revolution rate, and the nonlinear analysis is generally necessary when the hole curvature is larger than five degrees per thirty meters. The effects of dynamic factors should be considered when the revolution rate of drill string is higher than seventy revolutions per minute.