科研之友
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摘要
Sedimentary rocks possess complex microstructures and require simplified descriptions in terms of averaged, or effective mechanical properties. Most conventional approaches to effective media use the concept of viscoelastic moduli to describe the frequency-dependent wave velocities and attenuation. However, for rock containing pore fluids, a single pair of bulk and shear moduli does not account for slow P-and S-waves and for reflections and conversions in heterogeneous media. To overcome these limitations, we use the general linear solid (GLS) theoretical framework to derive multiphase models of effective media. Two types of models are considered. First, for sandstone containing thin layers saturated with brine and gas, two-phase effective-medium relations are derived in a (relatively) closed form for the density and elasticity, and the parameters of internal friction are inferred by fitting the dispersion spectra of both fast and slow P-waves. In the second application, we consider the generalized standard linear solid (GSLS) medium, which is broadly used in numerical simulations of seismic wavefields. The GLS point of view suggests that (petro) physical significance should always be sought for the mathematical variables usually assumed in GSLS models. Inertial effects and interactions between internal variables cause additional wave modes in a GSLS medium. Contrary to what is often thought, with inertial effects and fuller interactions between the internal variables, near-zero or negative velocity dispersion can occur in a medium with band-limited attenuation.
- 出版日期2016-8
