Combination Dynamic Seal Design Of Rotary Steering Drilling Tool

Rotary steering drilling technology was developed in the late 20th century, which was a sophisticated automation drilling technology.The rotary steering drilling tool is mainly used in the extra-deep well, the highly difficult directional well, the horizontal well, the big displacement well and so on. It can adjust the well inclination flexibly and automatically. It represents the highest level of present drilling technology development.The work environment underground drilling is very bad, drilling fluid pressure and temperature changes with the depth. Drilling fluid contains debris, sand and other solid phase and other chemicals, these factors influence the effect of downhole seal directly. The design of domestic dynamic seal is still exist many problems, especially in such a high temperature and pressure, and poor working conditions, the sealing performance of the seals is far less than the required sealing requirements. So a new seal structure with automatic radial compensation characteristic is designed according to the working conditions to satisfy the dynamic sealing requirements, which improves the reliability and life of the underground dynamic seals.In this article, a brief analysis of the existing domestic structure of several common seal status and development direction has been carried on; The guide tools mechanical model is established for the optimal solution, and the best location and the size of the force, shaft deformation and stress distribution and the distortion of the influence of bottom sealing are obtained with finite element analysis, and the shaft fatigue life is analyzed. Then a new combination rotary seal which is composed of the mechanical seal, metal bellows and helical seal is designed. This paper makes a detailed design, calculation and analysis emphasis on bellows and mechanical seal. Bellows is the key parts to the combined sealing, which plays the function of the radial compensation, to eliminate impact of shaft bending deformation to back-end seal. The design of the bellows and the optimization of structural parameters are analyzed in detail. The influence of each parameters variation on its stiffness and stability, stress distribution are studied. Ultimately the best geometric parameter that meets its requirement is determined and the fatigue life is calculated. Finally, mechanical seal dynamic and static ring friction and wear and the deformation are analyzed and the thermal stress of sealing is carried out with finite element analysis, and some advices and measures are put forward to reduce its thermal stress. In the end, by the detailed calculation and analysis, the combined sealing satisfy the down-hole sealing requirements and has a high life span. This design provides a new design method for underground harsh environment dynamic seal designing.