双稳定器预弯曲钻具组合防斜特性动力学评价方法

直井的防斜打快一直以来都是钻井领域的难题。预弯曲底部钻具组合防斜打直技术利用预弯曲结构引导钻具组合变形产生较大的动态降斜力，可实现动力学防斜打快目的。然而预弯曲钻具组合防斜特性的动力学定量评价仍是难题。针对双稳定器预弯曲底部钻具组合，笔者在Jansen建立的动力学模型的基础上建立钻头处动态侧向力模型，将仿真得出的A截面处的涡动轨迹数据应用到动态侧向力计算中，最终通过涡动轨迹图、动态侧向力分布时程图和平均动态侧向力对此类钻具的防斜特性进行快速且直观的评价。最后通过编制的计算机程序对不同井斜角和转速条件下的防斜特性进行了仿真计算，仿真结果表明:（1）随井斜角增大，降斜力增大；（2）随转速提升，钻具防斜特性可分为稳定降斜、不稳定降斜及丧失降斜能力3个阶段；（3）在不同井斜角下，第一、第二临界转速随井斜角增大而增大。

Dynamic evaluation method of anti-deflection characteristics of double-stabilizer pre-bending BHA

Deviation control and fast drilling of vertical well has always been a difficult problem in the field of drilling. Pre-benting BHA technolog uses pre-bending structure to guide BHA deformation to produce large dynamic deflection reduction force, so as to realize the purpose of dynamic deviation prevention and fast drilling. However, the dynamic quantitative evaluation of deviation prevention characteristics of pre-bent BHA is still a difficult problem. Based on the dynamic model established by Jansen, the dynamic lateral force model at the bit is established. The eddy trajectory data of section A obtained from simulation is applied to the calculation of dynamic lateral force. Finally, the anti-deviation characteristics of this kind of drilling tools are evaluated quickly and intuitively through whirl trajectory diagram, dynamic lateral force distribution time history diagram and average dynamic lateral force. The simulation results show that: （1）With the increase of well deviation angle, the force of reducing inclination increases; （2）With the increase of rotating speed, the anti-deviation characteristics of drilling tools can be divided into three stages: stable, unstable and losing the ability of reducing deviation;（3） Under different inclination angles, the first and second critical speeds increase with the increase of well deviation angle. Through the study of the above models and laws, the mechanism of deviation prevention and declination of the pre bent BHA with double stabilizers is further revealed, which is of great significance to the application of pre bent BHA in the field.