Solazzi Santiago G, Castromán Gabriel A, Barbosa Nicolás D, Holliger Klaus, Rubino J Germán
YPF Tecnología S.A. (Y-TEC)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.
Institute of Earth Sciences, University of Lausanne, Lausanne, Switzerland.
J Acoust Soc Am. 2024 Aug 1;156(2):1324-1342. doi: 10.1121/10.0028324.
Patchy saturation is a term used in the seismic prospecting literature to describe the state of a geological formation in which two immiscible pore fluids prevail in mesoscopic-scale clusters. If the pore fluids have contrasting compressibilities, wave-induced fluid pressure diffusion (FPD) processes may induce significant attenuation and velocity dispersion on seismic waves. Biot's monophasic poroelasticity theory is widely used to model the seismic response of rocks containing binary patches of two immiscible pore fluids. Even though effective fluid approximations may help to represent more realistic partially saturated patches using Biot's monophasic equations, the so inferred dissipation may not be representative of actual biphasic FPD phenomena. In this work, Biot's equations for mono- and biphasic fluids are combined to model FPD processes in porous media, comprising fully and partially saturated patches. An analytical solution for one-dimensional layered patchy-saturated media is presented which permits to explain some, as of yet enigmatic, experimentally observed characteristics such as increased seismic attenuation and stiffening effects occurring at low saturations. The results show that the existence of an additional diffusive wave mode within partially saturated patches may render conventional binary and effective fluid approaches incorrect and error prone.
斑状饱和度是地震勘探文献中使用的一个术语，用于描述一种地质构造状态，即在介观尺度的簇团中存在两种不混溶的孔隙流体。如果孔隙流体具有不同的压缩性，波致流体压力扩散（FPD）过程可能会在地震波上引起显著的衰减和速度频散。毕奥单相孔隙弹性理论被广泛用于模拟含有两种不混溶孔隙流体二元斑块的岩石的地震响应。尽管有效流体近似法可能有助于用毕奥单相方程来表示更现实的部分饱和斑块，但如此推断出的耗散可能并不代表实际的双相FPD现象。在这项工作中，将毕奥单相和双相流体方程结合起来，以模拟多孔介质中的FPD过程，该多孔介质包括完全饱和和部分饱和的斑块。给出了一维层状斑状饱和介质的解析解，这有助于解释一些迄今仍难以捉摸的实验观测特征，如在低饱和度下出现的地震衰减增加和硬化效应。结果表明，部分饱和斑块内存在额外的扩散波模式可能会使传统的二元和有效流体方法变得不正确且容易出错。
