Research on Dynamic Measurement Method of Drilling Tool Attitude Near Bit Based on Suppression of Heavy-Tailed Measurement Noise

In the process of coalbed methane directional well drilling, drilling through coal seam and large trajectory deviation is easy to occur, the essence of which is that the near-drill bit measurement unit produces a large number of complex interference noise due to the impact vibration generated by the rotation of the drilling tool and the rock breaking of the drill bit, which seriously affects the accuracy of the attitude measurement of the drilling tool. Aiming at the complex measurement noise of near-bit dynamic measurement unit, a dynamic measurement method of drilling tool attitude near bit in coalbed methane directional well based on heavy-tailed noise suppression is proposed in this article. First, the principle of near-bit dynamic measurement and the influencing factors of near-bit dynamic measurement are analyzed, and then the white noise and colored noise produced by the vibration of near-bit micro-electromechanical system (MEMS) accelerometer and gyroscope are filtered by unscented Kalman filter (UKF). Then, based on the Student's t-distribution model of noise characteristics, the acceleration filter model of heavy-tailed measurement filter (HTMF) is established to filter the measurement noise of heavy-tailed non-Gaussian distribution. Finally, an experimental platform of near-bit dynamic measurement software and hardware was built. The experimental results showed that the dynamic errors of borehole inclination and toolface were kept within +/- 0.1 degrees and +/- 0.2 degrees, respectively, on the vibration test platform, and the near-bit dynamic measurement errors caused by vibration were effectively suppressed.