CAREER: Impact of Mineralogy and Wettability on Pore-scale Displacement Mechanisms of Nonaqueous-Phase Liquids in Heterogeneous Rocks

地下水在美国和世界其他国家都是一种宝贵的资源。在许多情况下，人们在地下处置化学物质，要么是当时的最佳做法，要么是无意中的。在种类繁多的有机化学品中，许多在水中不是很易溶的。如果不溶于水的化合物进入地下，它们往往停留在被称为非水相液体(NAPL)的浓缩区。如果化学品比水轻，它们漂浮在地下水位的顶部，被称为L非水相液体；如果化学物质比水重(密度更高)，它们下沉到地下水位的底部，被称为D-NAPLS(稠密非水相液体)。这些液体的流动方式与地下水不同，因此可能停留在一个地方，成为长期的污染源。这个拟议的项目将研究岩石中的这些NAPL，那里的岩层在大小上不均匀分布(例如沙子)，而是在不均匀的岩石中或我们所说的非均质地层中。这些系统极其复杂，首席调查员将利用石油勘探的实验和建模工具开发人员，将这些系统应用于存在NAPL的较近的地表(但还包括地下)系统。通过更好地了解这些过程，我们将能够更好地管理我们的地下水资源，并提供水作为饮用水和灌溉的来源。PI将使用的工具将整合实验和建模方法。X射线计算机微层析成像将用于：i)在岩石样品中生成高分辨率的孔隙空间拓扑和矿物学(形状和组成)图，从中建立网络模型；以及(Ii)进行表征良好的现场流动实验，以测量流体的占有率和表面活性剂对相同岩石中NAPL修复的影响。将使用最先进的界面张力和接触角仪器来研究NAPLS对润湿性改变的影响。由于润湿力导致矿物表面、NAPL和水相之间的平衡状态，本研究将系统地考虑可能导致润湿性改变的NAPL/表面活性剂/水/矿物组合。将突出所测量的宏观属性和微观属性之间的差异。开发了一种新的动态孔隙尺度网络模型，用于岩心尺度上的两相流动模拟。该模型将在逐个孔隙的基础上明确考虑岩石矿物学中的非均质性和润湿性，以忠实地预测润湿性变化对非均质岩石中NAPL驱油机制的影响。与现有的准静态网络模型不同，动态孔隙尺度网络模型将结合基于物理和数学的严格处理孔隙尺度位移的复杂动力学，这些动力学解释了毛细、粘性和重力。它将使用最真实的孔隙空间拓扑表示，并在核心尺度上高度并行化处理网络模型。然后，该模型将与本工作中产生的实验数据进行严格验证，以预测表面活性剂增强的修复方法在各种NAPL/盐水/岩石系统中的性能。为了帮助传播这项研究的结果，该提案的教育部分有三个主要目标：(1)培养对科学和工程的兴趣，特别是在女性和少数族裔中；(2)通过导师和指导研究项目吸引本科生和研究生；以及(3)弥合当前科学和工程领域的进步与K12/本科教学课程、公共教育和服务之间的差距。新的“地下岩石之旅”将为6-12年级的学生提供一个难忘的机会，利用新建立的洞穴在多尺度岩石内部流动，从而促进他们的好奇心和科学兴趣。通过其“表面科学日”，该教育计划将通过帮助他们充分发挥潜力，提高社会和工作场所对未被充分代表的学生的接受度。

1351296GoualGroundwater is a precious resource in the US and other countries in the world. In many situations people have disposed of chemicals in the subsurface, either as a best practice at that time, or, unintentionally. Within the wide variety of organic chemicals many are not very soluble in water. If compounds that are not soluble in water enter the subsurface they tend to stay in concentrated zones referred to as non-aqueous phase liquids (NAPLs). If the chemicals are lighter than water they float on top of the water table and are referred to L-NAPLS (light non-aqueous phase liquids) and if the are heavier (more dense) than water they sink to the bottom of the water table and are referred to as D-NAPLs (dense non-aqueous phase liquids). These liquids do not move in the same manner as does the ground water and therefore may stay in one location acting as a long-term source of pollution. This proposed project will examine these NAPLs in rocks, where the rock strata are not evenly distributed in size (for example a sand) but rather in rocks that non-uniformed or what we refer to as heterogeneous formations. These system are extremely complex and the Principal Investigator, using experimental and modeling tools developer for oil exploration, will apply these to nearer surface (but yet sub-surface) systems where NAPLs exist. Through a better understanding of these processes we will be better able to manage our groundwater resources and provide water as a source of drinking water and for irrigation. The tools that the PI will use will integrate experimental and modeling methods. X-ray computed micro-tomography will be used: i) to generate high-resolution maps of pore space topology and mineralogy (shape and composition) in rock samples from which network models are made, and (ii) to perform well-characterized in-situ flow experiments to measure fluid occupancy and the effect of surfactants on NAPL remediation in the same rocks. The impact of NAPLs on wettability alteration will be examined using a state-of-the-art interfacial tension and contact angle apparatus. Because wetting forces lead to an equilibrium condition between the mineral surface, NAPL, and aqueous phase, this study will systematically consider NAPL/surfactant/water/mineral combinations that are likely to induce wettability alteration. Differences between measured macroscopic and microscopic properties will be highlighted. A novel dynamic pore-scale network model will be developed for two-phase flow simulations at the core-scale. The model will explicitly account for heterogeneities in rock mineralogy and wettability on a pore-by-pore basis to faithfully predict the impact of wettability alteration on NAPL displacement mechanisms in heterogeneous rocks. Unlike existing network models that are quasi-static, the dynamic pore-scale network model will incorporate physically based and mathematically rigorous treatment of the complex dynamics of pore-scale displacements that account for capillary, viscous, and gravity forces. It will use most realistic representations of pore-space topology and be heavily parallelized to handle network models at the core-scale.The model will then be rigorously validated against the experimental data generated in this work to predict the performance of surfactant-enhanced remediation methods in various NAPL/brine/rock systems.To help disseminate this the results of this research, the educational component of this proposal has three maingoals: (1) foster interest in science and engineering, especially among women and minorities;(2) engage undergraduate and graduate students through mentorship and guided research programs; and (3) bridge the gap between current progress in science and engineering and K12/undergraduate teaching curriculum, public education, and service. The new "Journey Into Underground Rocks" will provide grade 6-12 students with an unforgettable opportunity to move with the flow inside multi-scale rocks using a newly-established CAVE, thus promoting their curiosity and scientificinterest. Through its "Surface Science Days," the educational plan will contribute to increase the acceptance of underrepresented students in the society and work place by assisting them in reaching their full potential.