Dynamic Measurement of Well Inclination Based on UKF and Correlation Extraction

Abstract

While drilling, the drilling tool can reach the target layer more quickly and efficiently with the accurate borehole trajectory information. It can reduce the drilling cost. However, in the process of traditional well inclination measurement with drilling, due to the interference form the rotary vibration of drill string, the inclinometer needs to stop drilling to complete the measurement of drill tool attitude. And the sensor is installed far away from the drill, so the measurement error and the risk of well control are increased. In order to solve the problem that the interference of near the bit inclinometer which caused by complex shock vibration and drill string rotation, this paper proposes a method of dynamic measuring inclination angle that based on unscented kalman filter and cross-correlation extraction algorithm (UKF+CC). It is a composite filtering method that combine UKF, cross-correlation extraction algorithm, low pass filtering with sliding slide filtering. In this method, firstly, a limiter filter is used to filter the step excitation signal caused by impact noise. Then UKF filter is used to filter out the most colored noise caused by vibration acceleration, at the same time, low-pass filtering is used to deal with the magnetic interference noise in the output signal of tri-axis fluxgate, and using sliding filter to smooth the radial acceleration signal in the tri-axis acceleration sensor. Finally, the radial or tangential direction magnetic signal of the tri-axis fluxgate is used as the reference signal, and use reference signal to extract accurately the gravity acceleration component of the near bit position by cross-correlation detection method, then can finish the accurate calculation of dynamic well inclination angle. The results are verified by the simulation test and the simulation experiment of the rotating vibration test platform. When the drilling tool rotation speed within 60-300r/min, the maximum measurement error is +0.09°, the overall measurement accuracy of inclination angle under different drilling tool rotation speed is better than ±0.1°and the measured results are not affected by the rotation speed and vibration of drilling tool, it realizes the dynamic and accurate measurement of the inclination angle in the process of drilling.