双相介质中地震波的频率-空间域数值模拟

Simulation of wave propagation in two-phase porous media using a frequency-space domain method

本文利用优化的25点频率一空间域有限差分算法对基于BISQ模型双相各向同性介质中的地震波进行了数值模拟.通过与经典的Biot模型理论模拟结果进行对比,分析了Biot流动(宏观流体流动)和Squirt流动(微观流体流动)耦合作用对地震波在孔隙介质中传播特性的影响.数值模拟在地震频段进行,结果显示:在理想相界和黏滞相界情况下,Squirt流动机制都比Biot流动机制产生了更大的速度频散和能量衰减.其中,在Biot流动和Squirt流动耦合作用下的快P波的速度和振幅小于仅考虑Biot流动影响下快P波速度和振幅,而且慢P波的衰减也更加强烈.本文还研究了地震波在双层双相各向同性介质分界面处的反射和透射特征,双相介质中波的反射与透射现象类似于单相介质的情况.模拟结果表明,利用优化25点频率-空间域有限差分法模拟双相孔隙介质中的地震波场是可行的,这为开展双相孔隙介质全波形反演问题的研究提供了可能.

We implement a method of 25-point frequency-space domain finite difference obtain numerical solutions of the equations for two-phase isotropic media based on BISQ model.The modeling results of Biot theory and BISQ theory are compared and analyzed for providing insight into the coupling influence of Biot-flow（macroscopic）and Squirt-flow（microcosmic）on seismic waves.The numerical simulation is implemented within seismic frequency bandwidths,and the numerical results show that：for the two cases of ideal and viscous fluid,the Squirt-flow mechanism yields much higher velocity dispersion and attenuation than the Biot-flow mechanism.That is,under the coupling of Biot-flow and Squirt-flow,velocity and amplitude of fast P-wave are smaller than those only considering the Biot-flow,and attenuation of slow P-wave is higher.Meanwhile,we also investigate reflection and transmission at an interface separating two layers of two-phase isotropic media.The results are similar to the case for single-phase media.The study in this paper justifies that proposed method is effective and feasible to simulate wave propagation in two-phase porous media,and can be further applied in full waveform inversion in porous media.