基于改进广义S变换的井筒波压制

TUBE WAVE SUPPRESSION BASED ON THE IMPROVED GENERALIZED S-TRANSFORM

VSP资料中经常出现能量比较强的井筒波,目前其压制方法主要利用中值滤波和F-K滤波。由于中值滤波存在统计效应,而F-K变换经常存在空间假频,都很难取得理想效果。基于井筒波和有效信号的时频差异,提出利用改进的广义S变换(采用宽度可变的高斯窗函数,其时窗宽度随频率呈正比,在低频段时窗较窄,获得较高的时间分辨率;高频段时窗较宽,故可获得很高的频率分辨率)对井筒波进行分离和压制。理论推导和实际数据计算表明,基于吸收改进的广义S变换的井筒波压制明显突出了有效信号,提高了信噪比。

There is always strong tube wave in VSP data,and the current method of tube wave suppression are mainly the median filtering and F-K filtering.Since statistical effects of median filtering and false-frequency of F-K,it is difficult to achieve the desired effect.Based on the time-frequency difference between tube wave and effective signal,the improved generalized S transform(with variable width Gaussian window with the width in proportion to the frequency.When in low-frequency,time window is narrow and time resolution high.When in high-frequency,time window is wide and frequency resolution high) is used to isolate and suppress the noise.Theory and the actual data show that absorption attenuation theory which is based on the tube wave suppression has improved the signal,and achieves satisfied results.