Research on propagation properties of elastic waves in two-phase anisotropic media

Abstract

With the development of seismic engineering and seismic exploration of energy, the underground media that we study are more and more complicated. Conventional anisotropy theory or two-phase isotropy theory is difficult to describe anisotropic media containing fluid, such as fractures containing gas, shales containing water. Based on Biot theory about two-phase anisotropy, with the use of elastic plane wave equations, we get Christoffel equations. We calculate and analyze the effects of frequency on phase velocity, attenuation, amplitude ratio and polarization direction of elastic waves of two-phase, transversely isotropic media. Results show that frequency affects slow P wave the greatest among the four kinds of waves, i.e., fast P wave, slow P wave, fast S wave and slow S wave. Fluid phase amplitude to solid phase amplitude ratio of fast P wave, fast S wave and slow S wave approaches unit for large dissipation coefficients. Polarization analysis shows that polarization direction of fluid phase displacement is different from, not parallel to or reverse to, that of solid phase displacement in two-phase anisotropic media.