Abstract
Due to differences of rock properties such as porosity, permeability and compressibility between different regions in the porous media, pressure gradients are induced between those different regions and lead to local fluid flow. When seismic wave propagates in the porous media, the local fluid flow process is a main cause of wave attenuation and velocity dispersion. The local fluid flow mechanism of the layered porous model has been studied by many authors in the numerical approaches without analytical wave equations and solution for this kind of rock physics models. In this study, we first establish a layered double-porosity model saturated with a single fluid and derive the wave equations. According to the derived novel wave equations, then we calculate the phase velocity and quality factor in the layered double-porosity media based on plane wave analysis. The results demonstrate that there are three kinds of wave modes named as the fast P-wave and two slow P-wave in layered porous media when P-wave propagates through the model perpendicularly. Finally, we study the effects of local fluid flow on the mesoscopic loss mechanism by analyzing the attenuation and the velocity dispersion of seismic waves in the low frequency range.
Highlights
When seismic waves propagate in underground porous media saturated with fluid, pressure gradients are induced between different regions and lead to fluid flow relative to the solid
Chapman et al [2017] believed that the frequency scaling behavior of seismic attenuation is affected by the spatial distribution of the fluid, and they demonstrated this theory from the experimental investigation of the Berea sandstone saturated with two fluid phases.Local fluid flow (LFF) process induces wave attenuation and dispersion in the seismic frequency band when wave propagates in the porous media
The dry rock shear modulus of the model can be expressed as quency band, which can verify the correctness of the method in this work (Since the layered White model focuses on the attenuation and velocity dispersion of seismic waves in the low frequency range, the black solid lines have no attenuation peak and dispersion in the high frequency range)
Summary
When seismic waves propagate in underground porous media saturated with fluid, pressure gradients are induced between different regions and lead to fluid flow relative to the solid. Chapman et al [2017] believed that the frequency scaling behavior of seismic attenuation is affected by the spatial distribution of the fluid, and they demonstrated this theory from the experimental investigation of the Berea sandstone saturated with two fluid phases.Local fluid flow (LFF) process induces wave attenuation and dispersion in the seismic frequency band when wave propagates in the porous media. To study the effects of fabric and saturation inhomogeneities on wave attenuation and velocity dispersion, Ba et al [2017] proposed a double double-porosity model and derived the governing equations for this model based on Hamilton’s principle. We consider a layered double-porosity model to describe the wave-induced local fluid flow in porous layers, and analyze the mesoscopic loss mechanism due to LFF.
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