Abstract: To solve the problem of well deviation in Shuangyushi Block, We establish a model of drill bit deflection force with consideration of interaction between bit and formation, formation dip, inclination, angle, formation anisotropy index, formation deflection force and drill bit deflection force. And we explore the law of well deviation change under different influencing factors and verify the correctness of the model based on actual drill data. The results show that, compared with drilling fluid drilling, the formation deflection force increases under air drilling conditions. When the inclination angle is smaller than the formation dip, the formation force is a deflection force, which causes the drill bit to deviate upwards. Increasing the drilling pressure will cause the inclination angle to increase. As the formation dip angle increases, the natural forming force of the formation increases. As the inclination angle increases, the combined lateral force decreases. The resultant force of the bit has a balanced point. With the increase of the formation anisotropy index, the natural deflection ability of the formation increases, leading to the increase of the well inclination angle. According to the results of theoretical analysis, an integrated quantitative measure is proposed for drilling tool assembly, bit optimization, and drilling parameters, which reduces the inclination angle of ultra-deep formations with easy deflection to 0.50°～1.15ånd increases the ROP by 40%～85%. The results of this paper can provide important reference and guidance for the study and efficient control of ultra-deep well deviation rules.

Key words: Shuangyushi Block, deep well, well deviation, formation deflection force, comprehensive drill bit deflection force