Wave-induced fluid flow is considered to be a major source of seismic attenuation and dispersion in porous rocks. From the physical description of partially saturated reservoirs, numerous analytical solutions based on upscaling homogenization theories have been employed to calculate equivalent frequency-dependent poroelastic media. Nevertheless, dispersion and attenuation predictions are often not reasonably consistent with laboratory and field measurements in a broad frequency range, particularly due to influences of biphasic fluids and their distribution, presence of heterogeneities on various length scales, and pore microstructure. We investigate the role of pore microstructure on pressure and fluid saturation dependence of elastic velocities in tight sandstones. Previous work points out that differentiating the impacts of heterogeneities at various scales on dispersion within seismic exploration and sonic frequencies can be very difficult. In practice, this is because fluid-related dispersion mechanisms are impossible to be independent. Thus, it is important for a theoretical and more quantitative analysis of the relative contribution of interrelated energy dissipation processes through a better understanding of combined influences due to the presence of microscopic and mesoscopic heterogeneities. Based on microscopic squirt flow and mesoscopic flow in a partially saturated medium, we develop a poroelastic model that allows evaluating the overall frequency-dependent dispersion via considering a random distribution of fluid heterogeneities as well as the broadly distributed aspect ratio of compliant pores. Experimental validation of the model is accomplished via a comprehensive comparison of predictions with measurements of partially saturated velocities versus pressure and fluid for sandstones with specific pore microstructures.

中文翻译：

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压力和流体对孔隙微结构致密岩石声响应影响的室内实验与理论研究

波浪引起的流体流动被认为是多孔岩石中地震衰减和分散的主要来源。根据部分饱和储层的物理描述，许多基于放大均质化理论的解析解已被用来计算等效的频率相关的多孔弹性介质。然而，色散和衰减预测通常与宽频率范围内的实验室和现场测量不一致，特别是由于双相流体及其分布、各种长度尺度上存在不均匀性以及孔隙微观结构的影响。我们研究了致密砂岩中孔隙微观结构对弹性速度的压力和流体饱和度依赖性的作用。先前的工作指出，区分不同尺度的非均质性对地震勘探和声波频率的色散的影响可能非常困难。实际上，这是因为与流体相关的分散机制不可能是独立的。因此，通过更好地理解由于微观和介观异质性的存在而产生的综合影响，对相互关联的能量耗散过程的相对贡献进行理论和更定量的分析非常重要。基于部分饱和介质中的微观喷射流和介观流，我们开发了一种多孔弹性模型，该模型允许通过考虑流体非均质性的随机分布以及顺应性孔隙的广泛分布的纵横比来评估总体频率相关色散。该模型的实验验证是通过对具有特定孔隙微结构的砂岩的部分饱和速度与压力和流体的测量进行全面比较来完成的。