基于小波模极大值的测井信号滤波

Logging Signals Filter Based on Wavelet Modulus Maximum

脉冲中子-中子测井(PNN)热中子计数率曲线滤波处理是获取有效地层宏观俘获截面值的研究基础。针对PNN测井信号受到统计起伏的噪声干扰问题,在分析小波变换模极大值特性的基础上,分析PNN测井信号和干扰噪声的小波变换模极大值在不同尺度上的传播特性,建立PNN测井信号小波变换模极大值去噪算法。以油田某井为例,实现对PNN测井短源距计数率曲线的滤波处理。结果表明,基于小波变换模极大值的滤波方法能够有效去除PNN测井信号噪声干扰,提高测井信号的信噪比。

On the basis of thermal neutron count curve filter in Pulsed Neutron-Neutron （PNN） logging, the effective formation macroscopic capture cross section can be obtained. Because the interference of statistic fluctuation on PNN logging signals, the spread characteristics of wavelet transform modulus maximum of the signals and noise in different scales are discussed based on the investigation of modulus maximum characteristics. Proposed is an effective PNN logging signals preprocessing method wavelet transform modulus maximum filtering method. For case study, PNN logging SSN curves in a well are filtered by db4 wavelet. The practical application result shows that the wavelet modulus maximum effectively removes the noise and improves the signal to noise ratio of PNN logging signals.