随钻动态测井过程中加速度信号提取研究

Research on the accelerometer signal extraction in dynamic logging while drilling

在瓦斯抽采过程中,为了提高钻孔轨迹的测量精度,通常采用实时动态测量,然而钻具破岩造成的强振动和强冲击使得随钻测量系统中的三轴加速度计信号严重失真,无法精确测量钻具姿态。钻具钻进时X、Y轴方向的加速度计信号为周期信号、Z轴为直流信号,且陀螺仪对振动不敏感,因此,提出基于互相关算法和限幅递推平均滤波算法的加速度计信号提取方法。根据陀螺仪信号得出工具面角计算方程,使用傅里叶变换提取出参考信号,通过X、Y轴方向加速度计信号与参考信号的互相关运算,得到对应方向上的重力加速度分量,使用贝塞尔滤波和限幅递推平均滤波进行Z轴方向加速度计信号二次滤波,完成重力加速度的提取。仿真结果表明,井斜角的测量误差平均小于0.5°,动态测量精度得以提高。

In the process of gas drainage,in order to improve the measurement accuracy of borehole trajectory,real-time dynamic measurement is usually used.The strong vibration and impact caused by the drilling rock-broken rock make the signal of the triaxial accelerometer in the MWD system seriously distorted,which makes it impossible to accurately measure the attitude of drilling tool.During drilling,accelerometer signals in X and Y axes are periodic signals and dc signals in Z axis,and gyroscope is insensitive to vibration.Therefore,an accelerometer signal extraction method based on cross-correlation and amplitude limiting recursive average filtering algorithm is proposed.Firstly,the tool surface angle calculation equation is obtained according to the gyroscope signal,and the reference signal is extracted by Fourier transform.Then,the gravity acceleration component in the corresponding direction is obtained by cross-correlation calculation between the X and Y direction accelerometer signals and the reference signals.Finally,Bessel filter and amplitude limiting recursive average filter are used for secondary filtering of Z axis accelerometer signal to complete the extraction of gravity acceleration.The simulation results show that the deviation measurement error is less than 0.5°,and the dynamic measurement accuracy is improved.