ABSTRACT Wave‐induced fluid flow plays an important role in affecting the seismic dispersion and attenuation of fractured porous rocks. While numerous theoretical models have been proposed for the seismic dispersion and attenuation in fractured porous rocks, most of them neglect the wave‐induced fluid flow resulting from the background anisotropy (e.g. the interlayer fluid flow between different layers) that can be normal in real reservoirs. Here, according to the theories of poroelasticity, we present an approach to study the frequency‐dependent seismic properties of more realistic and complicated rocks, i.e. horizontally and periodically layered porous rock with horizontal and randomly orienting fractures, respectively, distributed in one of the two periodical layers. The approach accounts for the dual effects of the wave‐induced fluid flow between the fractures and the background pores and between different layers (the interlayer fluid flow). Because C33 (i.e., the modulus of the normally incident P‐wave) is directly related to the P‐wave velocity widely measured in the seismic exploration, and its comprehensive dispersion and attenuation are found to be most significant, we study mainly the effects of fracture properties and the stiffness contrast between the different layers on the seismic dispersion and attenuation of C33. The results show that the increasing stiffness contrast enhances the interlayer fluid flow of the layered porous rocks with both horizontal and randomly orienting fractures and weakens the wave‐induced fluid flow between the fractures and the background pores, especially for the layered porous rock with horizontal fractures. The modelling results also demonstrate that for the considered rock construction, the increasing fracture density reduces the interlayer fluid flow while improves the dispersion and attenuation in the fracture‐relevant frequency band. Increasing fracture aspect ratio is found to reduce the dispersion and attenuation in the fracture‐relevant frequency band only, especially for the layered porous rock with horizontal fractures.

中文翻译：

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具有不同方向裂缝的层状多孔岩石中的地震频散和衰减

摘要 波激流体流动在影响裂缝性多孔岩石的地震频散和衰减方面起着重要作用。虽然已经提出了许多关于裂缝性多孔岩石中地震频散和衰减的理论模型，但大多数都忽略了由背景各向异性（例如不同层间的层间流体流动）导致的波浪诱导流体流动，这在实际储层中可能是正常的. 在这里，根据多孔弹性理论，我们提出了一种研究更现实和复杂岩石的频率相关地震特性的方法，即水平和周期性层状多孔岩石，分别具有水平和随机取向的裂缝，分布在两个岩石中的一个。周期性层。该方法考虑了裂缝和背景孔隙之间以及不同层之间（层间流体流动）的波浪诱导流体流动的双重效应。由于 C33（即垂直入射 P 波的模量）与地震勘探中广泛测量的 P 波速度直接相关，并且发现其综合频散和衰减最为显着，因此我们主要研究了不同层间断裂特性和刚度对比对 C33 地震频散衰减的影响。结果表明，刚度对比的增加增强了具有水平和随机取向裂缝的层状多孔岩石的层间流体流动，并削弱了裂缝与背景孔隙之间的波浪诱导流体流动，特别适用于具有水平裂缝的层状多孔岩石。建模结果还表明，对于所考虑的岩石构造，裂缝密度的增加减少了层间流体流动，同时改善了裂缝相关频段的弥散和衰减。研究发现，增加裂缝纵横比只会降低裂缝相关频段的弥散和衰减，尤其是对于具有水平裂缝的层状多孔岩石。