关键词: 闭环钻井, 大位移井, 导向, 钻具组合, 运动学, 动力学, 小扰动理论, 传递函数

Abstract: The downhole closed-loop drilling technology is a new developing technology. It is indispensable to the success of extended reach well. The steering assembly is the key tool of the downhole closed-loop drilling system, and its mechanics properties are the base of downhole closed-loop control. The characteristic of the rotary steering assembly is similar to that of the rotary missile. By referring to the analyzing method used in the flying mechanics, the force analysis was made to the steering assembly and relative kinematics equations and dynamics equations were established in this paper. With the perturbation theory, the dynamics equations were linearized and the transfer functions for steering assembly of the downhole closed-loop drilling system were solved. The characteristics of the transfer functions were also analysed. The results and studying method will be useful to the downhole closed-loop drilling system.

Key words: closed-loop drilling, extended reach drilling, steering bottom hole assembly, kinematics, dynamics, perturbation theory, transfer function