摘要
横向各向同性(TI)介质是岩石地球物理中常见的一种现象,研究其井孔声场传播特征对声波测井理论以及为声波测井解释提供依据具有重要意义。针对具有垂直对称轴的横向各向同性(VTI)介质,根据柱坐标系条件下的弹性波波动方程,推导了速度—应力交错有限差分公式,采用时间二阶、空间十阶的交错有限差分算法对VTI介质中的井孔声场进行数值模拟。给出了在均匀介质中井孔声场不同时刻的波场快照,以及不同各向异性系数的VTI介质中的波场快照,计算了井轴上声源激发出的声波全波列波形。结果表明,在其他条件不变的条件下,VTI地层的各向异性系数的增大对横波的传播影响不大,但会使得纵波在纵向上的传播速度相对变小,径向上变化不大。各向异性系数的增大会使声波测井全波列首波信号时差变大,声波幅度略变小。
Transversely isotropic(TI) media is a common petrophysical media. It is important to study the propagationcharacteristics of the acoutic field in the well for sonic logging theory, and it can provide the basis for thesonic log interpretation. This paper derived velocity–stress staggered-grid finite-difference equations of the elasticwave propagation in cylindrical coordinates for vertical transversely isotropic(VTI) media. Furthermore, it numericallysimulated acoustic propagation in the VTI media using finite–difference technique with two orders in time andten orders in space. It gave the snapshots of borehole acoustic wave field in the homogeneous media at differenttimes and calculated the full wave trains with acoustic sources located at the well axis. The calculated resultsshow that if the coefficient of anisotropy of VTI media increases, the change of shear wave propagation has little effect, butthe velocity of longitudinal wave propagation has been reduced relatively in the longitudinal direction, and has little changein the radial direction. And if the coefficient of anisotropy of VTI media increases, the first wave slowness of sonic loggingwill increase, and the acoustic amplitude will be slightly reduced.
作者
岳崇旺
王飞
YUE Chongwang;WANG Fei(School of Geology Engineering and Geomatics, Chang′an University, Xi′an 710054, China)
出处
《煤田地质与勘探》
CAS
CSCD
北大核心
2016年第4期125-131,共7页
Coal Geology & Exploration
基金
国家青年自然科学基金项目(41504090)
中央高校基金基础研究项目(310826161021
310826161014)~~
关键词
交错网格有限差分
高阶
VTI
介质
井孔声场
staggered-grid finite–difference
high–order
VTI media
borehole acoustic field
