联合EMD和分数阶Fourier变换的裂缝性火成岩地层纵波和横波时频特征  

Time-frequency characteristics of P and S waves in fractured igneous formation based on joint EMD and fractional Fourier transform

作　　者：徐方慧 王祝文[1] 王文华[2] 齐兴华 崔裔曈 韩锐羿 XU Fanghui;WANG Zhuwen;WANG Wenhua;QI Xinghua;CUI Yitong;HAN Ruiyi(College of GeoExploration Science and Technology,Jilin University,Changchun 130026,China;College of Earth Sciences,Jilin University,Changchun 130021,China)

机构地区：[1]吉林大学地球探测科学与技术学院,吉林长春130026 [2]吉林大学地球科学学院,吉林长春130021

出　　处：《中国石油大学学报（自然科学版）》2021年第6期60-71,共12页Journal of China University of Petroleum(Edition of Natural Science)

基　　金：国家自然科学基金项目(41874135)。

摘　　要：为了研究裂缝性火成岩地层中纵波和横波的时频特征,联合经验模态分解(EMD)和分数阶Fourier变换对阵列声波测井信号进行滤波。首先通过EMD得到高频的IMF,再利用分数阶Fourier变换的旋转特性分离高频IMF中的纵波和横波,得到不同角度裂缝对应的纵波和横波Choi-Williams分布。结果表明:联合EMD和分数阶Fourier变换能有效改善纵、横波的时频耦合;相对于致密地层,裂缝性火成岩地层中的纵波和横波均幅值衰减、主频降低,同时速度减小。一般地,纵波幅值衰减与裂缝倾角呈正相关,横波幅值则相反;对于低角度裂缝,横波比纵波更敏感;纵波和横波主频在低角度裂缝和高角度裂缝地层中的差别不大;纵波和横波的速度在穿过低角度裂缝后降低更严重。In order to study the time-frequency characteristics of the primary wave(P wave)and shear wave(S wave)in fractured igneous formation,array acoustic logging signals are filtered by combining EMD and fractional Fourier transform.First,the high-frequency IMFs are extracted from the array acoustic signal by the EMD,and then the P and S waves are separated by using the rotation of fractional Fourier transform.Finally,the Choi-Williams distributions of P and S waves corresponding to different angle fractures are obtained.The results show that the joint EMD and fractional Fourier transform can improve the time-frequency coupling of P and S waves.The energy,dominant frequency and velocity of P and S waves in fractured igneous formation are lower than those in tight formations.Generally,the higher the dip angle of fracture,the greater the attenuation of P wave energy and the smaller the attenuation of S wave energy.The dominant frequency of P and S waves has little difference between low angle fracture and high angle fracture.The velocity attenuation of P and S waves is stronger after passing through the low angle fracture.

关 键 词：裂缝性火成岩地层 纵波 横波 时频特征 EMD和分数阶Fourier变换 Choi-Williams分布 

分 类 号：P631[天文地球—地质矿产勘探]