Dynamic effects in capillary pressure-saturations relationships for two-phase flow in 3D porous media: Implications of micro-heterogeneities
Dynamic effects in capillary pressure-saturations relationships for two-phase flow in 3D porous media: Implications of micro-heterogeneities
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DOI：
10.1016/j.ces.2006.12.039
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发表时间：
2007-04-01
影响因子：
4.7
通讯作者：
Das, Diganta Bhusan
中科院分区：
文献类型：
--
作者：
Mirzaei, Mahsanam;Das, Diganta Bhusan
毛细管压力-饱和度（P-c-S）关系是表征多孔介质中两相流动行为的关键。然而，这些关系并不是唯一的，并且取决于流动动力学，即稳态或动态，以及其他因素。研究表明，描述多孔介质中两相流过程的经验模型可能不足以充分解释动态条件下的流动物理。提出了新的毛细管压力关系，其中包括一个额外的项，以说明毛细管压力对饱和度和饱和度的时间导数的依赖（偏导数S/偏导数t）。该参数是毛细管阻尼系数，也称为动态系数（tau），它确定了达到流动平衡的速度。P-c-S关系对偏导数S/偏导数t的依赖称为动态效应。在大多数测量两相流特性的实验室实验中，隐含地假设样品是均匀的。然而，情况并非如此，具有不同多相流特性的微非均质可能存在于畴内。它们影响了区域内多流体相的动力学和饱和度分布。这些问题已经被单独研究过，但P-c-S关系的动态效应和微观尺度异质性的结合还没有被准确量化，特别是在3D领域。因此，文献中报道的tau值存在显著的不确定性。在这项工作中，我们进行了数值研究，探讨了微观尺度非水相液体（DNAPL）的存在如何影响致密非水相液体（DNAPL）的动力学和水在多孔域的流动。微尺度非均质性的性质、强度和分布变化在动态流动条件下的相对重要性体现在P-c-S曲线上，该曲线用动态系数tau量化。影响P-c-S曲线的各种因素（如动态流动条件、微观非均质性分布和强度、孔径分布、畴大小、几何形状和介质各向异性）之间存在复杂的相互作用。然而，我们的结果表明，在所有其他因素保持不变的情况下，随着非均质性强度的增加，给定饱和度下的动力系数也会增加。区域形状（圆柱形与矩形）、宽高比、维度（213 vs 3D）、渗透率各向异性对tau的影响也进行了分析，以便尽可能地推广它们的影响。我们设想，我们的模拟将尽量减少文献中有关tau的报告数据的一些不一致之处。(c) 2007 Elsevier Ltd.版权所有。
The capillary pressure-saturation (P-c-S) relationships are essential in characterising two-phase flow behaviour in porous media. However, these relationships are not unique and depend on the flow dynamics, i.e., steady state or dynamic, among other factors. It has been shown that empirical models describing two-phase flow processes in porous media may be inadequate to account fully for the physics of flow in dynamic conditions. New capillary pressure relationships have been proposed which include an additional term to account for the dependence of capillary pressure on saturation and time derivative of saturation (partial derivative S/partial derivative t). This parameter is a capillary damping coefficient, also known as dynamic coefficient (tau), which establishes the speed at which flow equilibrium is reached. The dependence of P-c-S relationships on partial derivative S/partial derivative t is called dynamic effects.In most laboratory experiments for measuring two-phase flow properties, it is implicitly assumed that the sample is homogeneous. However, this is not the case and micro-heterogeneities with their distinct multiphase flow properties may exist within the domain. They affect the dynamics of the multiple fluid phases and saturation distributions in the domain. These issues have been studied individually but the combination of dynamic effects and micro-scale heterogeneities on the P-c-S relationships has not been quantified accurately, particularly in 3D domains. Consequently, there are significant uncertainties on the reported values of tau in the literature.In this work, we have carried out a numerical study to investigate how the presence of micro-scale heterogeneities affects the dynamics of dense non-aqueous phase liquid (DNAPL) and water flow in porous domain. The relative significance of the variations in nature, intensity and distribution of micro-scale heterogeneities on dynamic flow conditions are manifested on P-c-S curves which are quantified in terms of the dynamic coefficient, tau. There is a complex interplay of various factors (e.g., dynamic flow conditions, distribution and intensity of microheterogeneity, pore size distribution, domain size and geometry and media anisotropy) which affects P-c-S curves. However, our results show that as the intensity of heterogeneity increases the dynamic coefficient at a given saturation increases, provided all other factors remain the same. The effects of domain shapes (cylindrical vs. rectangle), aspect ratios, dimensionality (213 vs. 3D), permeability anisotropy on tau are also analysed in order to generalise their effects as far as possible. We envisage that our simulations will minimise some of the inconsistencies on the reported data on tau in the literature. (c) 2007 Elsevier Ltd. All rights reserved.