裂缝介质弹性波场数值模拟及波场特征

NUMERICAL MODELING AND CHARACTERISTIC ANALYSES OF THE ELASTIC WAVEFIELDS IN THE FRACTURE MEDIA

裂缝介质的数值模拟是研究裂缝介质中地震波传播特征及规律的主要手段。以各向异性介质的弹性波动方程为基础,推导出空间交错网格方法一阶导数的任意偶数阶精度差分格式,并利用此差分格式对裂缝介质进行了2.5D三分量正演模拟。模拟结果表明:受裂缝影响弹性波在裂缝介质中传播的波场是非常复杂的,除了存在反射P波、反射P-SV波,还存在横波分裂现象和沿裂缝介质传播的导波等;数值模拟的三分量的方位道集呈现出波场传播的时间和振幅与裂缝的方位存在很大的关联,其方位各向异性特征与实际资料的方位各向异性特征一致,可以指导今后的方位各向异性处理和裂缝预测。

The numerical modeling of Fracture media is the main method to study the propagation characteristics and rules of the seismic waves in underground fracture media. On the basis of the elastic wave equation of the anisotropic media,the scheme of the precision difference is presented for random even order of the first order of the spatial staggered grid formulations,and moreover with the help of the above scheme,the forward modeling for 2. 5D components is conducted for the fracture media. The simulation results show that due to the influences of the fractures,the wave fields of the elastic waves propagating in the fracture media are rather complex: besides there are P- wave and P- SV wave,the following phenomena and so forth occur: the shear wave splitting and guided wave propagated along the fracture media; there are great connection with the fracture azimuths for the time and amplitude of the wave field propagation in the three- component azimuth gathers of the numerical simulation,their azimuth anisotropy characteristics are consistent with those of the real data,thus the future azimuth anisotropy processing and fracture predication can be guided.