| Rotary Steerable Drilling technology is the most advanced drilling technology being developed by many countries throughout the world. There is no product of the rotary steerable drilling tool in china, while there are many commercial tools oversea. In order to change this situation, we need to study the rotary drilling tool more deeply, and design it as soon as possible. This paper presents the working principle and structure of three typical rotary steerable drilling tools, and focus on Point-the-bit rotary drilling tool, especially make a great research and analysis on its deflection mechanism.This paper firstly chose the deflection mechanism of the Point-the-bit rotary drilling tool for the research subject based on the comparison with the two typical rotary drilling tools, and determined the function and the composition of the deflection mechanism; secondly made a mechanical analysis of the deflection mechanism, especially established and analyzed the mechanics model of the drilling shaft in different conditions, and then got the optimal deflection point of the drilling shaft and the deflection mechanism’s driving and braking torque; thirdly based on the driving and braking torque, designed the all parts of the mechanism, especially designed and calculated the harmonic drive and the electromagnetic clutch & brake which is innovative design. The optimal deflection point derived in this paper is very important, for the stress on the defection mechanism setting on the optimal point is most small, and then the design requirements of the deflection mechanism will be lower. The deflection mechanism is the key of the rotary steerable drilling tool, and its design is the first thing of all.In the final part of the paper, the conclusion approved the mechanical analysis of the deflection mechanism, the mechanics model of the drilling shaft, the optimal deflection point and the design of the mechanism, and also pointed out the short parts of the paper which need to be improved. |
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