液力-磁耦合自旋转井眼清洁工具的旋转传动机理研究

The rotation of the hydraulic blades of the hole cleaning tool causes the tangential velocity of the drilling fluid in the annulus. The tangential velocity of the drilling fluid can enhance the cutting carrying efficiency, and thus effectively inhibit the formation of the cuttings bed, especially for the highly deviated and horizontal well sections in horizontal wells and extended reach wells. Then, the efficiency of the hole cleaning is significantly improved. If downhole motor or coiled tubing drilling is applied when drilling in the build-up section, the hole cleaning tool can no longer rotate and assist hole cleaning. It is because that the rotation of most of the hole cleaning tools relies on the torque transmitted by drill pipe. In order to solve these problems, a scientific concept about hydraulic-magnetic coupling transmitting mechanism is proposed in the project. According to this concept, permanent magnet material acts as the transmission medium of the torque for the hole cleaning tool. Then transforming potential energy of the pressure of the drilling fluid to the kinetic energy of the rotation of the blades of the hole cleaning tool. Thus, the rotation of the hole cleaning tool can be achieved as long as the drilling fluid circulation is maintained. In addition, the hole cleaning tool is compatible to the downhole motors for slide drilling and to the coiled tubing drilling. The study on the scientific issues related to the hydraulic-magnetic coupling transmission mechanism will be conducted in this project, and detailed information is given as follows: the magnetic field distribution,the sensitivity analysis on magnetic transmission and calculation methods maximum torque transmitted by permanent magnet materials; energy-transformation mechanism of the hydraulic-magnetic coupling transmission system and the influence factors and change rules of output power of the hydraulic-magnetic coupling transmission system, etc.

井眼清洁工具水力叶片旋转作用可以使环空钻井液产生周向诱导速度，有效抑制水平井、大位移井大斜度和水平井段岩屑床的形成，提高钻井液携带岩屑效率。但目前井眼清洁工具多通过钻杆传递扭矩旋转，当造斜段使用井下动力钻具滑动钻进或连续油管钻井时该工具无法旋转辅助携屑。为解决滑动钻进和连续油管钻井时井眼清洁工具无法旋转的问题，申请人提出了液力-磁耦合自旋转传动机理的科学假设，该传动机理以永磁材料为扭矩传动介质，将钻井液压力势能转换为井眼清洁工具叶片的旋转动能，只要钻井液正常循环条件下即可实现井眼清洁工具的自旋转，滑动钻进工况和连续油管钻井均可应用。项目针对如何实现液力-磁耦合自旋转传动涉及的科学问题开展研究，包括：液力-磁耦合自旋转传动磁场强度分布规律、磁传动敏感性分析与磁传动极限扭矩的计算方法、液力-磁耦合自旋转传动压力势能与动能转换机理以及液力-磁耦合自旋转传动输出功率的影响因素与变化规律等。

在水平井，大位移井钻井过程中，井眼清洁工具的使用可以良好的应对井筒中岩屑沉积问题。液力-磁耦合井眼清洁工具的发明更可以实现在井下动力钻具滑动钻进中无钻杆提供扭矩情况下井眼清洁工具自主运转，抑制岩屑床的形成，提高井眼清洁效率。液力-磁耦合井眼清洁工具工作机理是钻井液循环的情况下，液压涡轮将钻井液的流动势能转换为内磁轴旋转的动能，经磁力传动透过工具壳体传递磁力和扭矩，带动壳体外侧岩屑清洁叶片旋转，从而实现井眼清洁。本研究基于磁库仑法、数值模拟法和磁场拉普拉斯方程建立磁扭矩分析模型，分析各参数对磁场强度，极限扭矩的影响变化规律，并设计液力-磁耦合井眼清洁工具室内实验模型进行验证；基于CFD数值模拟方法，建立液力-磁耦合井眼清洁工具涡轮压差叶片模型，对直叶型与扭曲叶片工作特性进行研究；基于欧拉双流体模型（TFM）结合分子运动理论（KTGF）建立清洁叶片清砂模型，采用旋流强度和旋流衰减系数表征岩屑清洁效果，进行不同形状叶片在多因素影响下的清砂效果模拟，优化叶片结构。研究表明：工具与5寸钻杆配套使用磁传动机构建议采用负-正Halbach阵列，永磁铁覆盖面积选择为100%全覆盖，壳体厚度为9~10mm，永磁铁厚度9.5~10.5mm，产生的磁扭矩最大；涡轮叶片为扭曲叶片，涡轮压降减少，其综合水力性能得到了提升；清洁叶片螺旋角越大叶片诱导的螺旋流衰减的速度越快，抵抗壁面摩擦的能力越弱，叶片旋转速度和叶片高度越大诱导螺旋流的衰减速度越慢，其抵抗壁面摩擦的能力越强；考虑各机构间摩擦阻力，工具正常运转需钻井液提供能量不小于55瓦。综合以上研究，设计研发第一代新型HCT-DB5-168型井眼清洁工具已在大庆油田应用15口井，累计节约钻井成本104.5万元，2020年相关发明专利以“普通许可”方式授权钻井服务公司应用。