Redundant posture measurement and system reconfiguration method of steering drilling tool

Real-time downhole posture measurement of steering drilling tool is vital to realize exact reliable control on the well trajectory of modulated steering drilling tool. Aiming at the poor reliability of measurement system under atrocious working environment, this study proposes a posture measurement method based on nonorthogonal quadri-axle gravity accelerometers, and the corresponding posture parameter solution and signal effectiveness judgment formulas are also given. As for inaccurate posture parameter under the status of small borehole deviation, a nonorthogonal measurement method is proposed, which depends on the quadri-axle gravity accelerometers installed with an initial tilt, so as to improve the measurement accuracy. To cope with problems that the accelerometer tends to fail or be destroyed in atrocious downhole environment, a measurement method is presented based on dual redundant nonorthogonal quadri-axle gravity accelerometers. Then the mutual conversion formula between relative signals of dual redundant gravity accelerometer is given. Moreover, this study discusses the judgment method and diagnosis process of gravity accelerometer fault based on signal characteristics, based on which a system reconfiguration scheme is established accordingly. The hydraulic driving test results indicate that tool posture measurement is accurate, and the stable control of platform angle is achieved.