We present a solute transport model, developed by employing a dynamic pore network modeling approach, to investigate dispersive solute transport behaviors in consolidated porous media. The model is capable of upscaling solute transport processes from pore to core, under two-phase fluid configurations. The governing equations of fluid flow, fluid displacement, and solute transport are solved at the pore level. A heavily parallelized computing scheme is utilized to simulate dynamic fluid displacements and transport processes in a core-scale pore network constructed from micro-computed tomography (micro-CT) images of a Berea sandstone sample. A series of solute transport simulations are conducted under the single-phase condition to validate the model by comparing the computed longitudinal dispersion coefficients against the experimental data over a wide range of Peclet numbers (Pe), i.e., 3×10-2∼3×105\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$3 \times 10^{-2}{\sim}3 \times 10^5$$\end{document}. The model is then used to simulate solute transport under two-phase fluid configurations to examine the effects of the non-wetting phase saturation on solute transport behaviors. More specifically, solute transport is studied at different Pe and different water saturations obtained at the end of imbibition processes. We find that in a two-phase system, the longitudinal dispersion coefficient substantially increases with enhanced convective mixing under the transport regime with high Pe but decreases with restricted diffusive mixing at low Pe. In addition, the results indicate a non-monotonic dispersion–saturation relation under the convective transport condition. We illustrate that a strong correlation exists between the extent of dispersive mixing and the heterogeneity of fluid saturation profile across a core-scale network.

中文翻译：

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使用动态孔隙网络建模方法在稳态两相流条件下进行溶质输运的孔隙到核心放大

我们提出了一种通过采用动态孔隙网络建模方法开发的溶质输运模型，以研究固结多孔介质中的弥散溶质输运行为。该模型能够在两相流体配置下放大从孔隙到核心的溶质传输过程。流体流动、流体位移和溶质输运的控制方程在孔隙水平上求解。利用高度并行化的计算方案来模拟由 Berea 砂岩样品的显微计算机断层扫描 (micro-CT) 图像构建的核心尺度孔隙网络中的动态流体位移和输运过程。在单相条件下进行了一系列溶质输运模拟，通过将计算的纵向色散系数与在很宽的 Peclet 数 (Pe) 范围内（即 3×10-2∼3×）的实验数据进行比较来验证模型105\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin} {-69pt} \begin{document}$$3 \times 10^{-2}{\sim}3 \times 10^5$$\end{document}。然后使用该模型来模拟两相流体配置下的溶质输运，以检查非润湿相饱和度对溶质输运行为的影响。进一步来说，研究了不同 Pe 下的溶质迁移和在渗吸过程结束时获得的不同水饱和度。我们发现，在两相系统中，纵向分散系数在高 Pe 传输状态下随着对流混合增强而显着增加，但在低 Pe 下随着扩散混合受限而降低。此外，结果表明在对流传输条件下存在非单调色散-饱和关系。我们表明，分散混合的程度与核心尺度网络中流体饱和度剖面的异质性之间存在很强的相关性。纵向分散系数在高 Pe 传输状态下随着对流混合的增强而显着增加，但在低 Pe 下随着受限扩散混合而降低。此外，结果表明在对流传输条件下存在非单调色散-饱和关系。我们说明，分散混合的程度与核心尺度网络中流体饱和度剖面的异质性之间存在很强的相关性。纵向分散系数在高 Pe 传输状态下随着对流混合的增强而显着增加，但在低 Pe 下随着受限扩散混合而降低。此外，结果表明在对流传输条件下存在非单调色散-饱和关系。我们表明，分散混合的程度与核心尺度网络中流体饱和度剖面的异质性之间存在很强的相关性。