自动垂直钻具井下流场特性研究

自动垂直钻井系统在工作中,导向活套与钻杆要有一个相对转速。导向活套在与钻杆连接轴承的摩擦转矩的作用下而随钻杆转动,而井下返程泥浆在通过活套时也会产生阻碍活套转动的反向扭矩,该反向扭矩是保证活套与钻杆存在相对转速的一个关键因素。利用FLUENT软件包对活套井下泥浆流场进行建模仿真,揭示了泥浆通过活套时的流动特性。计算结果表明泥浆对活套的反向扭矩取决于泥浆的流量、活套转速等多种因素,且只要钻杆转速超过平衡钻杆与活套的摩擦转矩的临界转速,该反向扭矩就可以使活套与钻杆间产生相应的转速差。

STUDY ON THE CHARACTERISTICS OF THE DOWNHOLE FLOW FIELD IN THE AUTOMATIC ANTI-DEVIATION DRILLING SYSTEM

When the automatic anti-deviation drilling system is in operation,a relative rotation speed is needed between the steering sleeve and drill pipe.The steering sleeve rotates as a result of the friction torque exerted by the bearing connecting the sleeve and the drill pipe while the downhole backtracking mud will also produce a reversal torque which prevents the sleeve from rotating when passing it.The reversal torque is the key factor to ensure the relative rotation speed.FLUENT software package can be used to model the mud flow field downhole and explore the flow behaviour.Simulation results indicate that the reversal torque depends on several factors such as mud flow,rotation speed of the sleeve,etc.And as long as the rotation speed of the drill pipe exceeds the critical speed which balances the friction torque of drill pipe and the sleeve,the reversal torque can produce relevant speed difference between the sleeve and drill pipe.