SUMMARY

Wave-induced fluid flows (WIFF) can be viewed as cases of broader local-deformation (LD) phenomena and represent the principal causes of seismic-wave attenuation in fluid-saturated porous rock. Most existing WIFF models refer to greatly simplified microstructures and specific flow patterns, such as planar divergent flows within thin cracks (squirt flows, SF) or flows within patchy-saturation zones. However, such microstructures represent only idealized mathematical models that may be impossible to consistently identify within a given rock. At the same time, most details of such microstructures are insignificant for seismic waves, which are only sensitive to averaged properties of the medium. To perform microstructure-independent modelling of LD effects, we develop a simple yet general approach based entirely on a macroscopic local-deformation variable. This variable is broadly analogous to Biot's fluid content and is illustrated for two specific microstructural models. The macroscopic model is Biot-consistent and uses only time- and frequency-independent material properties. Both local and global (Biot's) pore flows and all types of waves and deformations are explained in a rigorous and consistent manner. The model allows constraining a minimal set of material properties responsible for all observed elastic and anelastic effects in porous rock. Because of making no assumptions about the microstructures and their spatial scales, this approach should comprise at least some of the existing WIFF models. In particular, this model accurately reproduces all attenuation and velocity dispersion spectra predicted by a broadly used SF model. The model also contains effects not considered previously, such as bulk viscosity of pore fluid and viscous coupling between the rock frame and fluid-filled pores. The model offers straightforward extensions to multiple porosities and cases of viscous fluids in primary pores. Based on the resulting differential equations, physically consistent schemes for numerical modelling of seismic wavefields can be developed for porous rock with arbitrary LD effects.

中文翻译：

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流体饱和多孔岩局部变形效应的简单通用宏观模型

概要

波浪感应流体流动（WIFF）可以看作是更广泛的局部变形（LD）现象的案例，它们代表了流体饱和的多孔岩石中地震波衰减的主要原因。现有的大多数WIFF模型都涉及大大简化的微观结构和特定的流型，例如细裂缝内的平面发散流（喷流，SF）或斑片状饱和区内的流。但是，这样的微结构仅代表理想化的数学模型，可能无法在给定的岩石中一致地进行识别。同时，这种微结构的大多数细节对于地震波而言并不重要，而地震波仅对介质的平均特性敏感。为了执行LD效应的与微观结构无关的建模，我们开发了一种完全基于宏观局部变形变量的简单而通用的方法。该变量大致类似于Biot的流体含量，并针对两个特定的微观结构模型进行了说明。宏观模型是Biot一致的，并且仅使用与时间和频率无关的材料属性。严格和一致的方式解释了局部和全局（比奥）的孔隙流动以及所有类型的波浪和变形。该模型允许约束负责在多孔岩石中观察到的所有弹性和非弹性效应的最小材料属性集。由于未对微结构及其空间尺度进行任何假设，因此该方法应至少包括一些现有的WIFF模型。特别是，该模型准确地再现了由广泛使用的SF模型预测的所有衰减和速度色散谱。该模型还包含以前未考虑的影响，例如孔隙流体的整体粘度以及岩石框架和充满流体的孔隙之间的粘性耦合。该模型可以直接扩展到多个孔隙以及初级孔隙中粘性流体的情况。基于所得的微分方程，可以为具有任意LD效应的多孔岩石开发物理一致的地震波场数值模拟方案。该模型可以直接扩展到多个孔隙以及初级孔隙中粘性流体的情况。基于所得的微分方程，可以为具有任意LD效应的多孔岩石开发物理一致的地震波场数值模拟方案。该模型可以直接扩展到多个孔隙以及初级孔隙中粘性流体的情况。基于所得的微分方程，可以为具有任意LD效应的多孔岩石开发物理一致的地震波场数值模拟方案。