Seismic waves passing through partially saturated porous rocks produce pressure gradients in the fluid phase, and, hence, the resulting fluid flow is accompanied by various length scales. The major mechanism responsible for seismic attenuation and dispersion is arguably known as wave-induced fluid flow between inhomogeneities of microscopic, mesoscopic and macroscopic scales. Previous studies have revealed that differentiating the influence of heterogeneities at various scales on wave attenuation within seismic exploration and sonic frequencies, nevertheless, is very difficult. This is because wave attenuation mechanisms due to different heterogeneities are practically impossible to be unrelated. Therefore, it is important for a more quantitative interpretation of the relative contribution of inter-dependent energy loss mechanisms through improved understanding of the combined influences associated to the microscopic squirt flow and mesoscopic fluid flow. We introduce a scaled poroelastic model to evaluate frequency-dependent attenuation and velocity dispersion characteristics by considering the combined presence of microscopic and mesoscopic heterogeneities. To do so, the capillarity effects are incorporated into the poroelastic model with random distributions of the sizes of mesoscopic-scale heterogeneities. A range of pertinent scenarios are calculated, and the acoustic properties indicate wave attenuation decreases whereas the phase velocity increases corresponding to additional capillary forces. Meanwhile, numerical results of the proposed model were compared with experimental measurements of a tight sandstone to examine its validity. Results of numerical simulations suggest that seismic reflections produce more complicated signatures in the presence of an interbedded structure of a reservoir exhibiting velocity dispersion. Therefore, the proposed procedure can help in assessing the sensitivities of frequency-dependent seismic signatures to reservoir fluid mobility and patch heterogeneities.

中文翻译：

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使用具有细观和微观非均质性的多孔弹性模型分析波衰减和速度色散的频率相关特性

穿过部分饱和的多孔岩石的地震波在流体相中产生压力梯度，因此，由此产生的流体流动伴随着不同的长度尺度。造成地震衰减和分散的主要机制可以说是微观、细观和宏观尺度的不均匀性之间的波浪诱导流体流动。先前的研究表明，区分不同尺度的异质性对地震勘探和声频中的波衰减的影响是非常困难的。这是因为不同异质性引起的波衰减机制实际上不可能不相关。所以，通过更好地理解与微观喷射流和细观流体流相关的综合影响，对相互依赖的能量损失机制的相对贡献进行更定量的解释很重要。我们引入了一个缩放多孔弹性模型，通过考虑微观和介观异质性的组合存在来评估频率相关的衰减和速度色散特性。为此，毛细作用效应被纳入多孔弹性模型中，其具有细观尺度异质性大小的随机分布。计算了一系列相关场景，声学特性表明波衰减减小，而相速度增加对应于额外的毛细管力。同时，将建议模型的数值结果与致密砂岩的实验测量结果进行比较，以检验其有效性。数值模拟结果表明，在存在速度弥散的储层互层结构的情况下，地震反射会产生更复杂的特征。因此，所提出的程序可以帮助评估频率相关地震特征对储层流体流动性和斑块非均质性的敏感性。