基于Bond变换的裂缝介质波场方位特征模拟及分析  

Seismic wavefield simulation and azimuth feature analysis for fractured media based on Bond transformation

作　　者：李小斌 阎建国[1] LI XiaoBin;YAN JianGuo(School of Geophysics,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]成都理工大学地球物理学院,成都610059

出　　处：《地球物理学进展》2021年第5期2034-2044,共11页Progress in Geophysics

基　　金：中国石油科技重大科技专项(2017E-0402)资助。

摘　　要：地震波场的方位特征对于裂缝性油气藏的地震预测方法研究有着重要的意义.为使裂缝模型更具一般性,本文基于线性滑动理论和Bond变换构造了两组任意夹角竖直裂缝模型;考虑到波场二维模拟中突出方位特征,依据弹性动力学的基本方程和Bond变换,推导出了含方位角的弹性波传播速度应力方程;使用高精度交错网格有限差分法对几种裂缝介质进行了数值模拟,并分析其波场特征的变化.模拟结果表明,在两组参数相同的任意夹角竖直裂缝模型中,裂缝内夹角各个方位的波场特征变化不明显,各向异性强度较低,裂缝外夹角各个方位的波场特征变化剧烈,裂缝正交时,各处波场特征相近;针对单组裂缝模型,分析了裂缝参数变化对波场特征的影响,总结出了三种波场形态,得出了裂缝垂直面的波场特征与裂缝法向弱度和切向弱度的相对大小有关,从裂缝垂直面到裂缝平行面的波场朝着相同的形态变化,与裂缝参数无关等认识.这些分析结果有助于进一步认识和应用裂缝介质的波场方位特征.The seismic wavefield azimuth characteristics are significant in the study of seismic prediction methods for fractured oil and gas reservoirs. This paper constructs two sets of vertical fractured models with arbitrary angles, based on the linear sliding theory and Bond transformation to develop a generic fractured model. The azimuth characteristics are also considered in the two-dimensional wavefield simulation. According to the fundamental equations of elastic dynamics and Bond transformation, the elastic propagation velocity-stress equation with azimuth angle is derived and the high-precision staggered-grid finite difference method is used to simulate several fractured media. Thereafter, the wavefield characteristics of the models are analyzed. Simulation results reveal that for the models with two groups of vertical fractures having the same parameters and arbitrary angles, the wavefield characteristics exhibit minor change and the anisotropy strength is observed to be low in the fractured interior angle azimuth, whereas, the wavefield characteristics change drastically in the fractured exterior angle azimuth. When the fractures are orthogonal, similarly oriented wavefield characteristics are obtained. The influence of variations in the fracture parameters on the wavefield characteristics of the single group of fractured models is analyzed, and the three wavefield patterns are summarized. The wavefield characteristics of the fractured vertical plane are affected by the relative magnitudes of shear and normal weakness. From the fractured vertical to the fractured parallel planes, the wavefield changes towards a similar shape and is not affected by crack parameters. The results of this study further help to understand and apply the wavefield azimuth characteristics of the fractured media.

关 键 词：线性滑动理论 裂缝介质 有限差分 全方位 数值模拟 Bond变换 

分 类 号：P631[天文地球—地质矿产勘探]