CAREER:Advanced interface methods in heterogeneous porous materials: a multi-disciplinary and multi-scale framework

许多自然和人工过程涉及两种或三种流体相（如水、油和空气）在多孔介质中的同时流动。然而，预测相位移动的速度以及它们是否可以被恢复并不是微不足道的。它需要了解复杂三维空间中不同流体的拓扑结构，从简单的土壤到根-土壤系统，从均匀的砂岩到断裂的碳酸盐岩。多孔介质（土壤或岩石）和流体性质（即哪种流体优先润湿岩石表面）决定了多种流体在孔隙中竞争时的最终空间分布。此外，微小的岩石或土壤孔隙通常控制着哪些流体被困住以及在哪里被困住。对复杂几何形状和不同润湿性孔隙中流体的空间分布进行量化仍然是一个尚未解决的基本问题。该项目的目标是从第一性原理出发探索和量化动态空间流体排列及其对多孔介质流动复杂性的控制。为了实现这一目标，该项目将开发一种灵活的、多尺度的数值方法来描述非均质润湿性多孔材料中的两相和三相流动形态。通过合作，两流和三相流构型的x射线微层析成像的详细三维实验数据将用于数值方法的输入和验证。结果将使不同润湿性、多孔介质粗糙度和流体最终排列的岩石表面的量化和升级到更大的感兴趣的空间区域。应用的一个例子是德克萨斯州的爱德华兹含水层，它为奥斯汀和圣安东尼奥大都会地区的大约200万人提供水。含水层由非均质灰岩组成，与砂/砾石沉积物互层叠加。另外，流动路径的非均质性来自断层和裂缝：95%的流动发生在高导电性裂缝网络中，而95%的水储存在岩石基质中。裂缝网络导电性和基质储藏量之间的差异，再加上高度不稳定的降雨，是德克萨斯州中部水资源管理问题的核心。当下雨时，水通过裂缝以极快的速度流出系统（从而导致山洪暴发）；经过一段干燥期后，由于非均质储层的润湿性变化和水/空气竞争，储层基质可能满90%，但井通常会变得干燥。在这种非均质介质（也称为喀斯特）中控制污染物的泄漏引入了孔隙空间中三种流体相的竞争。无论这个具体的例子如何，拟议研究的结果将与许多不同的研究领域相关，例如枯竭油藏中的二氧化碳封存以及补救和提高石油采收率的努力。结果将在现有理论和模型的外推到混合湿、两和三流体相系统中具有重要意义。此外，与本提案一起启动的多孔材料数字图像存储库将增强多孔介质理论、模型和实验的研究基础设施和基准。最后，喀斯特地层和水管理问题是德克萨斯州日常经验的一部分，它们是教育广大读者了解地质学、流体物理和化学、工程学以及应用数学和计算机科学的理想选择。这个项目的结果将由美国国家科学基金会和美国能源部资助的专业发展项目的教师进行测试，然后整合到可访问的在线模块中，并包括在奥斯汀儿童博物馆的互动展览中。

Many natural and artificial processes involve the simultaneous flow of two or three fluid phases (such as water, oil, and air) through porous media. However, the prediction of how fast the phases move and whether they can be retrieved is not trivial. It requires knowledge of the topology of different fluids in a complex three-dimensional space that ranges from simple soil to root-soil systems, and from a uniform sandstone to fractured carbonate rocks. Both porous media (soil or rock) and fluid properties (i.e. which fluid is preferentially wetting the rock surface) determine the final spatial distribution when multiple fluids are competing within pores. Furthermore, minuscule rock or soil pores often control which fluids become trapped and where. Quantifying the spatial arrangement of fluids in pores of complex geometry and varying wettability remains an unsolved fundamental problem. The project objective is to explore and quantify dynamic spatial fluid arrangements from first principles and their control on flow complexity of porous media. To address the objective, the project will develop a flexible, multiscale numerical method to describe two- and three-fluid phase flow configurations in porous materials of heterogeneous wettability. Through cooperation, detailed 3D experimental data imaged with x-ray microtomography of two and three-phase flow configurations will be available for both input and verification of the numerical method. Results will enable the quantification and upscaling of rock surfaces of different wettability, porous media roughness and the ultimate arrangement of fluids to larger spatial regions of interest.One example region of application is the Edwards Aquifer in Texas, which provides water for approximately two million people in the Austin and San Antonio metropolitan areas. The aquifer is formed by heterogeneous limestone, inter-bedded and overlain with sand/gravel sediments. Additional flow-path heterogeneity originates from faults and fractures: 95% of the flow occurs in a highly conductive fracture network, whereas 95% of water storage is in the rock matrix. The difference between fracture network conductivity and matrix storage, combined with highly erratic rainfall, are at the core of water management issues in central Texas. When it rains and water moves through fractures and out of the system exceedingly fast (thereby causing flash flooding); after a dry period, due to wettability changes and water/air competition in this heterogeneous reservoir, the storage matrix might be 90% full, but wells often become dry. Controlling a contaminant spill in such a heterogeneous medium (also known as karst) introduces the competition of three fluid phases in the pore space. Regardless of this specific example, the findings of the proposed research will become relevant to many different fields of research such as carbon dioxide sequestration in depleted oil reservoirs and in remediation and enhanced oil recovery efforts. Results will be of significant use in the extrapolation of existing theory and models to mixed wet, two- and three-fluid phase systems. In addition, a digital image repository for porous materials initiated along with this proposal will enhance research infrastructure and benchmarking of porous media theory, models and experiments. Finally, karst formations and water management issues are part of the everyday experience in Texas and they are ideal to educate a broad audience on geology, flow physics and chemistry, engineering as well as applied mathematics and computer science. Results from this project will be tested by teachers at professional development projects funded by the NSF and DOE, and then integrated into accessible online modules and included in an interactive exhibit in the Austin's Children Museum.