井下动液面声波信号处理方法研究

Research on acoustic signal processing method of downhole moving liquid level

石油采收过程中油井动液面深度监测对确保油井的安全生产非常重要。当使用声波法测量油井动液面深度时,受到套管中复杂结构的影响,井口接收到的声波信号的接箍波和液面回波易受到噪声的干扰,导致传统的信号处理方法很难计算声波的速度和旅行时间,从而无法获得油井动液面深度。针对这一问题,首先对接箍波进行巴特沃斯低通滤波,采用短时平均幅度差函数来获取接箍波的平均采样次数,以此来计算声波在油井中传播的速度;在此基础上,对液面回波进行小波去噪,采用小波奇异值检测方法来获取液面回波位置,以此来计算起爆波和液面回波位置的时间差,进而实现油井动液面深度的检测。为了更加直观方便地对比处理效果,设计了基于MATLAB的可视化数据处理软件。选取多组采油现场获得的声波信号进行测试,结果表明,测量绝对误差控制在1 m以内,相对误差不超过0.075%,与其他信号处理方法(相对误差范围0.3%~0.5%)相比,所提的方法误差较小,能够较好地满足实际工程中的需求。

In the process of oil recovery,the depth monitoring of the oil well′s fluid level is very important to ensure the safe production of the oil well.When the acoustic method is used to measure the dynamic liquid level depth of oil well,the coupling wave and the liquid level echo of the acoustic signal received by the wellhead are easily interfered by the noise due to the influence of the complex structure in the casing.As a result,it is difficult for the traditional signal processing method to calculate the velocity and travel time of the acoustic wave,so the dynamic liquid level depth of oil well can not be obtained.In order to solve this problem,this paper firstly conducts Butterworth low-pass filter for coupling wave,and uses short-time mean amplitude difference function to obtain the average sampling times of coupling wave,so as to calculate the propagation velocity of acoustic wave in oil well.On this basis,the liquid level echo was denoised by wavelet,and the liquid level echo position was obtained by using the wavelet singular value detection method,so as to calculate the time difference between the detonation wave and the liquid level echo position,and then realize the detection of the dynamic liquid level depth of oil well.In order to compare the processing effect more intuitively and conveniently,this paper designs a visual data processing software based on MATLAB.This paper selects multiple sets of acoustic signals obtained from oil production sites for testing.The results show that the absolute measurement error is controlled within 1 m,and the relative error does not exceed 0.075%.Compared with other signal processing methods(relative error range 0.3%~0.5%),the proposed method has less error and can better meet the needs of actual engineering.