摘要
声波衰减对裂缝识别更为敏感,因此在非常规油气勘探和压裂监测等领域有着广泛的应用前景.裂缝型油气储层非均质性强,散射效应显著,但长波长假设下的等效介质理论无法准确描述散射导致的声波衰减.本研究利用交错网格有限差分方法,在二维随机裂缝介质上模拟了标量横波(SH波)的传播,并研究了裂缝尺度、密度以及交叉对横波散射衰减的影响.研究发现,裂缝长度l_(c)、裂缝密度γ和背景介质波数k_(0)可定量表征散射衰减.裂缝长度l_(c)小于背景介质波长λ_(0)的1/30时,可以忽略散射衰减;当k_(0)l_(c)/2<1时,衰减随着k_(0)l_(c)/2的增大而增大,反之,衰减随着k_(0)l_(c)/2的增大而减小;当l_(c)≈λ_(0)/3时,衰减最强.裂缝交叉会加强k_(0)l_(c)/2<1时的散射衰减,而减弱k_(0)l_(c)/2>1时的衰减.这种定量关系有助于理解多尺度裂缝的横波散射衰减特征,对声波测井和勘探地震中的裂缝识别问题具有实用价值.
Acoustic attenuation demonstrates higher sensitivity to crack identification compared to velocity,thus holding significant potential for applications in unconventional oil and gas exploration and hydraulic fracturing monitoring.Cracked reservoirs exhibit strong heterogeneity,with significant scattering effects.However,the effective medium theory based on the long-wavelength assumption fails to accurately describe the acoustic attenuation caused by scattering.In this study,the propagation of scalar shear waves(SH waves)was simulated on two-dimensional random cracked media using the staggered-grid finite-difference method.The effects of crack scale,density,and intersection on shear wave scattering attenuation were investigated.It was found that when the crack length(l_(c))is less than 1/30 of the background medium wavelength(λ_(0)),scattering attenuation can be neglected.Additionally,attenuation increases with k_(0)l_(c)/2 when k_(0)l_(c)/2<1,and decreases when k_(0)l_(c)/2>1.The strongest attenuation occurs when lc is approximately equal toλ_(0)/3.Cracks intersection amplifies scattering attenuation when k_(0)l_(c)/2<1 while weakening scattering attenuation when k_(0)l_(c)/2>1.The relationship between crack length(l_(c)),crack density(γ),and background medium wave number(k_(0))quantitatively characterizes scattering attenuation.This relationship aids in understanding the shear wave scattering attenuation characteristics of multi-scale cracks,with practical implications for crack identification in sonic logging and exploration seismic.
作者
周浩
符力耘
曹辉
俞军
邓继新
ZHOU Hao;FU LiYun;CAO Hui;YU Jun;DENG JiXin(College of Geophysics,Chengdu University of Technology,Chengdu 610059,China;School of Geosciences,China University of Petroleum(East China),Qingdao Shandong 266580,China;Key Laboratory of Well Logging,Petro China,Research Institute of Petroleum Exploration&Development,Beijing 100083,China)
出处
《地球物理学报》
北大核心
2025年第2期668-679,共12页
Chinese Journal of Geophysics
基金
国家自然科学基金青年项目(42304144)
中国石油天然气股份有限公司测井重点实验室开放基金(2023-KFKT-26)资助.
关键词
声波衰减
裂缝识别
裂缝散射
谱比法
多尺度裂缝
Acoustic attenuation
Crack identification
Crack scattering
Spectral ratio method
Multi-scale cracks
