Research On MWD Algorithm For Wellbore Trajectory Based On MEMS

The features of low power consumption,low cost and small size that MEMS inertial sensors having,which are very suitable for MWD in a small space.The measurement accuracy of MEMS inertial sensors can not meet the MWD engineering applications' requirements,so this paper studies the measurement accuracy of MEMS inertial sensors.In order to improve the measurement accuracy of MEMS inertial sensors,this paper studies it in depth.This paper uses the NANO-IMU produced by the American MEMSENSE company to calibrate and compensate the system error of its MEMS triaxial gyroscope,MEMS triaxial accelerometer and MEMS triaxial magnetometer,and restrain the random error by wavelet filtering.Finally,this paper studies wellbore trajectory while drilling measurement methods and verified by experiments.Specific research work includes the following aspects:(1)The paper deeply investigates the development of wellbore trajectory while drilling measurement and MEMS inertial sensors at home and abroad,and summarizes and studies the basic principles and measurement methods of wellbore trajectory while drilling measurements,and determines the research direction of this paper.(2)Baesd on the engineering environment and equipment characteristics of the MWD,the error modeling and calibration of the MEMS triaxial gyroscope,MEMS triaxial accelerometer and MEMS triaxial magnetometer in the device NANO-IMU are carried out by using Matlab software.Calibration of the zero offset drift of the MEMS triaxial gyroscope by static state measurement.The ellipsoid fitting method is used to calibrate the installation error,scale factor error and zero offset drift of MEMS triaxial accelerometer and MEMS triaxial magnetometer.Three types of inertial sensors were calibrated separately to verify the effectiveness of their calibration.(3)For the random error in the process of wellbore trajectory while drilling measurement,the method of wavelet filtering is used for suppression.The test method of threshold,wavelet function and decomposition layer number selection is designed,and the corresponding Matlab program is edited.According to the NANO-IMU equipment properties,the above parameters are selected,and the effectiveness of wavelet filtering for random error suppression of measurement data is verified by experiments.(4)Two wellbore trajectory measurement methods based on magnetometer and accelerometer,gyroscope and accelerometer and coordinate calculation methods are studied.The correctness of the measurement method based on magnetometer and accelerometer is verified by experiments.The results of attitude angle calculation before and after the error processing further demonstrate that the accuracy of inclination,tool face angle and azimuth calculation are greatly improved.