A flexible drilling tool is a special drilling tool for ultrashort-radius radial horizontal wells. This tool is composed of many parts and has the characteristics of a multibody system. In this paper, a numerical method for the dynamic analysis of flexible drilling tools is proposed. The flexible drill tool is discretized into spatial beam elements, while the multilayer contact of the flexible drilling tool is represented by the multilayer dynamic gap element, and the dynamic model of the multibody system for the flexible drilling tool’s multilayer contact is established, considering the interaction force between the drill bit and the rock. The nonlinear dynamic equation is solved using the Newmark method and Newton–Raphson method. An analysis of the dynamic behavior of a flexible drilling tool is conducted. The results indicate that the flexible drilling tool experiences vortex formation due to the interaction between the flexible drilling pipe and the guide pipe, leading to increased friction and wear. This situation hinders safe drilling operations with flexible drilling tools. The collision force of the flexible drilling tool near the bottom of the hole is more severe than that of the other tool types, which may lead to failure of the connection.

柔性钻具是超短半径径向水平井专用钻具。该工具由许多部分组成，具有多体系统的特征。本文提出了一种柔性钻井工具动态分析的数值方法。将柔性钻具离散成空间梁单元，并用多层动态间隙单元表示柔性钻具的多层接触，考虑相互作用，建立了柔性钻具多层接触的多体系统动力学模型。钻头与岩石之间的作用力。使用Newmark 方法和Newton-Raphson 方法求解非线性动力学方程。对柔性钻井工具的动态行为进行了分析。结果表明，由于柔性钻杆与导管之间的相互作用，柔性钻具会形成涡流，导致摩擦和磨损增加。这种情况阻碍了灵活钻井工具的安全钻井作业。柔性钻具在孔底附近的碰撞力比其他钻具类型更严重，可能导致连接失败。