径向振动对旋转钻柱摩阻扭矩的影响

Influence of radial vibration on the torque and drag of rotary drill string

大位移井已被广泛应用于非常规油气资源的勘探开发当中,但在大位移井大斜度稳斜段钻进过程中,如果扭矩过大易造成钻柱失效,而目前关于水平段径向振动对于旋转钻柱摩阻扭矩影响规律的研究则较少,并且多集中于产生径向振动工具研制和摩擦系数测量等方面。为此,在分析径向振动对于旋转钻柱摩阻扭矩影响原理的基础上,设计了不同型号截面外形为椭圆形的钻杆减磨接头模型;采用自行研制的减摩降扭工具性能试验装置,对不同钻速、转速条件下安装有不同钻杆接头模型的水平旋转钻柱进行扭矩测试;进而探究了径向振动对钻柱摩阻扭矩的影响规律。研究结果表明:①随钻杆接头椭圆截面长短轴半径比的增大,扭矩均值和扭矩波动最大幅值均先减小后增大,长短轴半径比为1.065时,扭矩的均值和最大幅值均明显降低,可以起到减摩降扭的作用;②减小钻速和转速,可以降低扭矩均值;③转速超过45 r/min后,扭矩最大幅值随转速的增加变化不大;④扭矩波动基频与转速呈近似线性关系,与钻速和长短轴半径比无关。结论认为,该研究成果可以为大位移井水平井钻柱接头设计与应用提供帮助。

Extended reach well has already been used widely in the exploration and development of unconventional oil and gas resources, but in the drilling process of its high-angle holding section, the drill string will get failed easily if the torque is too large. At present, the influence laws of radial vibration of horizontal section on the torque and drag of rotary drill string is rarely studied, while studies mostly focus on the development of radial vibration tools and the measurement of friction coefficient. After analyzing the influence principles of radial vibration on the torque and drag of rotary drill string, this paper designed different types of drill pipe wear reduction joint models with elliptical section. Then, the independently developed experimental device for testing the performance of torque and drag reducing tool was adopted to test the torque of the horizontal rotary drill string installed with different drill pipe joint models under different rates of penetration(ROP) and rotary speeds. Finally, the influence laws of radial vibration on the torque and drag of drill string were explored. And the following research results were obtained. First, as the radius ratio of major axis to minor axis of the elliptical section in the drill pipe joint increases, the average torque and the maximum torque fluctuation amplitude decrease first and then increase. When the radius ratio of major axis to minor axis reaches 1.065, the average torque and the maximum torque fluctuation amplitude decrease greatly, leading to an reduction of torque and drag. Second, the average torque can be decreased by decreasing ROP and rotary speed. Third, after the rotary speed exceeds 45 r/min, the maximum torque amplitude changes little with further increase of the rotary speed. Fourth, the fundamental frequency of torque fluctuation is in a nearly linear relation with the rotary speed, but no relation with ROP and radius ratio of major axis to minor axis. In conclusion, the research results can provide guidance for the design and application of drill pipe joints in extended reach wells and horizontal wells.