全频率小波去噪方法在随钻四极横波测井中的应用  

Application of full frequency wavelet denoising method in quadrupole logging while drilling

作　　者：许连明 XU Lian-ming(Key Laboratory of Shale Gas and Geoengineering,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Institute of Earth Science,Chinese Academy of Sciences,Beijing 100029,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院地质与地球物理研究所中国科学院页岩气与地质工程重点实验室,北京100029 [2]中国科学院地球科学研究院,北京100029 [3]中国科学院大学,北京100049

出　　处：《地球物理学进展》2018年第5期2034-2040,共7页Progress in Geophysics

基　　金：中国科学院战略性先导科技专项(XDA14020301)资助

摘　　要：论述了随钻条件下由于钻铤钻进、振动及泥浆循环产生的系统噪声的时频域分布情况及对阵列声波的影响,认为一般的时域或者频域滤波方法不能消除此噪声干扰提高声波数据信噪比,而常规的小波去噪方法只能除去高频噪声,无法对井孔低频噪声进行处理,这对于低频四极子声波信号提取带来很大麻烦.现场声波数据的质量是获得准确地层信息的关键,为提高声波采集信号质量,本文在带通滤波基础之上提出了针对小波低频分解系数的硬阈值函数处理.经慢地层随钻四极子模拟数据验证,该方法能够有效地去除低频噪声,提高信噪比,最高可达10 dB.处理后的阵列波形经加权频谱相关法频散处理,得到更为准确的地层速度,为进一步相关研究提供依据和参考.Borehole noise caused by collar＇s vibration and mud circulation in the time domain and frequency domain at the case of logging while drilling is presented,as well as its impact on array acoustics. In general, conventional filter methods in time or frequency domain can＇t remove noise effectively or improve the data.Traditional wavelet denoising can only delete noise in high frequency,doesn＇t work on borehole noise in low frequency,which bring big trouble for quadrupole acoustic signals＇ extraction in low frequency. The quality of field data is the key to get formation＇s accurate velocity,in order to improve the quality of acoustic data acquisition, here proposes an hard threshold function for approximate coefficients in low frequency after bandpass filter. After verification with synthetic data of quadrupole logging while drilling in slow formation,the method can effectively wipe off noise in low frequency and improve the ratio of signal to noise up to 10 dB at most. The array waveform after denoising can derive more accurate velocity by weighted spectrum semblance, which can be an important reference for denoising the low frequency systematic noise in acoustic logging while drilling.

关 键 词：小波去噪 随钻四极横波测井 阈值函数 信噪比 加权频谱相关图 

分 类 号：P631[天文地球—地质矿产勘探]