含水平裂隙黏弹介质中的井孔声场传播特征  

Propagation characteristics of acoustic waves in a borehole surrounded by a viscoelastic medium with horizontal cracks

作　　者：岳崇旺[1] 李晓春 徐继山[3] 冯波 Yue Chong-Wang;Li Xiao-Chun;Xu Ji-Shan;and Feng Bo(School of Geology Engineering and Geomatics,Chang’an University,Xi’an,Shanxi,710054,China;Inner Mongolia coal geological exploration(Group)company with limited liability;School of Resources and Geosciences,China University of Mining and Technology,Xuzhou 221116,China)

机构地区：[1]长安大学地质工程与测绘学院,陕西西安710054 [2]内蒙古煤炭地质勘查(集团)有限责任公司,内蒙古呼和浩特010010 [3]中国矿业大学资源与地球科学学院,江苏徐州221116

出　　处：《Applied Geophysics》2023年第4期469-478,670,671,共12页应用地球物理（英文版）

基　　金：funded by-the National Natural Science Foundation of China(nos.41504090,42042054 and 42177123)。

摘　　要：岩石介质具有粘滞性,黏弹性介质模型相对于弹性介质模型更为接近岩石介质的真实情况。裂隙介质是地球物理勘探中的一种常见现象,特别是水平裂隙在沉积岩薄互层中广泛发育。以Cole-Cole黏弹性介质为背景,基于Hudson裂隙介质理论,给出了纵横波速度、品质因子、各向异性与裂缝密度以及裂缝高宽比之间的关系。推导了含水平裂隙黏弹介质速度—应力方程的交错网格有限差分公式,对不同裂隙密度、不同高宽比介质条件下的井孔声场进行了数值模拟。模拟结果表明:井外地层中纵波和横波速度随裂隙密度增大而递减,振幅随裂隙密度增加而增加;井内纵波、横波的速度和振幅随裂隙密度的增加而减小。井外地层中的纵波速度随裂隙高宽比的增加而减小,纵波振幅横波速度和振幅受高宽比的影响较小;井内接收到的纵波的速度和振幅随裂隙高宽比的增加而减小,横波的速度受裂隙高宽比影响较小,横波的振幅随裂隙高宽比的增大而减小。Because of the viscous properties of rock,a viscoelastic model is closer to the real situation of rock media than an elastic model is.Cracks in the media are common geophysical phenomena.In particular,horizontal cracks are widely developed in the thin interbeds of sedimentary rock.Taking a Cole—Cole viscoelastic medium as the background medium,we compute the frequency-dependent velocities,quality factors,anisotropy coefficients,crack densities,and crack aspect ratios of P-and S-waves based on Hudson’s theory.We give the velocity–stress staggered finite-difference equations of the elastic wave propagation in a cylindrical coordinate system for a viscoelastic medium with horizontal cracks and numerically simulate acoustic propagation in the cracked medium with different crack densities and aspect ratios.The simulation results indicate that as the crack density increases outside a borehole the P-and S-wave velocities decrease and their amplitudes increase,in a borehole the P-and S-wave velocities and amplitudes decrease;as the crack aspect ratios increases outside a borehole the P-wave velocities decrease,its amplitudes change little and the S-wave amplitudes and velocities change little,in a borehole the P-wave velocities and amplitudes decrease and the S-wave velocities in a borehole change little,and the S-wave amplitudes decrease.

关 键 词：水平裂隙 Hudson理论 COLE-COLE模型 井孔声场 

分 类 号：P631[天文地球—地质矿产勘探]