FRACTURED AQUIFER CHARACTERIZATION USING SMART NON-NEWTONIAN TRACERS

研究人员：俄勒冈州立大学John S.Selker建议编号：EAR 1446915裂隙岩石含水层是美国许多地区和世界其他大部分地区唯一的水源。了解这些水以及水所输送的物质，对于提供和保护安全饮用水来说是至关重要的。此外，水流裂隙岩在矿床的形成和深部地热系统的发展中起着重要的作用。这项研究还将有利于从裂缝性储集层中提取石油和天然气，包括通过水力压裂产生的储集层。因此，这项研究既是理论上的，也是潜在的非常实用的。能够识别裂缝中流体流动路径的方法一直非常有限。这项研究将进行实验室实验，使用独特的流体，可以更有效地对主要流动路径进行采样。这些是非牛顿流体(例如，瓜尔胶和其他食品级流体)。提出的新方法寻求一种实用的方法来洞察裂隙岩石含水层和其他裂隙岩石系统中的流动。在实验室工作的同时，将在法国普洛梅尔的观测站进行现场实验，在那里已经为这种实验建立了一个独特的裂缝流场址。此外，两名本科生将参与这项研究。识别裂隙岩石中的主要流动路径、它们的连通性和它们的水力特性对于流体流动和溶质运输至关重要。示踪剂测试可以表征从实验室到野外的这些含水层的性质。经典示踪剂测试解释允许根据简化的传输模型定义平均“有效水力”孔径。这项研究将：1)开发一种使用非牛顿(“剪切稀化”)流体的创新示踪剂方法，以识别天然裂隙网络中优先流动路径的孔径分布；2)研究这些“智能”示踪剂的流动行为，了解它们的流变性，以便表征裂缝系统的水力特性。通过调整粘度，研究人员将能够选择允许流动的特定阈值或光圈大小，而较小的光圈将在凝胶填充的条件下基本上被“冻结”。这将在实验室和现场进行测试，以证明其在确定含水层性质方面的效用。剪切变稀流体在真实岩石孔隙中运动的实验观察将与流体传输的理论模型进行比较。此外，数值模拟将探索实验方法确定的假设(例如，稳定(非牛顿追水)与不稳定(水追逐非牛顿)流体置换)。在初步结果的基础上，现场实验方法将检验所提出方法的有效性。在示踪剂试验期间，将使用耦合延时探地雷达测量，以记录示踪剂所走的优先路径。该方法将在法国一个独特的、特征良好的裂隙花岗岩地层中进行测试，那里已经基于多种水文地球物理方法确定了完整的裂缝几何形状和水力特征。最后，数值模型将研究在这种情况下控制非牛顿流体流动传输的一阶参数的敏感性。与裂隙含水层水文地质学相关的理论概念将在实验室中提出和实验解决。

Title: Fractured Aquifer Characterization Using Smart Non-Newtonian TracersInvestigator: John S. Selker, Oregon State UniversityProposal Number: EAR 1446915Fractured rock aquifers are the only source of water in many parts of the United States and much of the rest of the world. Understanding these waters, and the materials that water transports, is critically needed for providing and protecting safe water drinking water. In addition, the role of water flow fractured rocks is important in the formation of mineral deposits and in the development of deep geothermal systems. This research will also benefit the extraction of oil and gas from fractured reservoirs, including those created by fracking. Thus, this study is both theoretical and potentially very practical in nature. Methods that can identify fluid flow paths in fractures have been very limited. This research will conduct lab experiments that will use unique fluids that can sample the major flow paths more effectively. These are the Non-Newtonian fluids (e.g., guar gum and other food grade fluids). The novel methods proposed seek a practical means of gaining insight into flow in fractured rock aquifers and other fractured rock systems. In parallel to the laboratory work, a field experiment will be performed at the observatory site of Ploemeur, France, where a unique fracture-flow field site has been established for just this kind of experiment. In addition, two undergraduate students will participate in the research.The identification of dominant flow paths, their connectivity, and their hydraulic properties in fractured rocks is critical for fluid flow and solute transport. Tracer testing can characterize such aquifer properties from laboratory to field scales. Classical tracer test interpretations allow defining a mean "effective hydraulic" aperture based on simplified transport models. This research will: 1) develop an innovative tracer approach using non-Newtonian ("shear-thinning") fluids to identify aperture distributions of preferential flow paths in natural fractured networks and 2) investigate flow behavior of these "smart" tracers, knowing their rheology, in order to characterize the hydraulic properties of fracture systems. By adjusting the viscosity, the research will be able to select for specific thresholds or aperture size that allow flow, while smaller apertures will be essentially "frozen" in a gel-filled condition. This will be tested in the laboratory and at the instrumented field site to demonstrate the utility in characterizing aquifer properties. The experimental observations of the movement of shear-thinning fluid in realistic rock apertures will be compared to theoretical models of fluid transport. Additionally, numerical modeling will explore the hypothesis identified by the experimental approach (e.g., stable (non-Newtonian chasing water) vs unstable (water chasing non-Newtonian) fluid displacement). Based on preliminary results, the field experimental approach will to test the validity of the proposed approach. Coupled time-lapse GPR measurement will be used during tracer tests in order to document the preferential paths taken by the tracer. The methodology will be tested in a unique, well-characterized fractured granitic formation in France where complete fracture geometry and hydraulic characteristic have already been defined based on multiple hydro-geophysical approaches. Finally, numerical models will investigate the sensitivity of first order parameters that control flow transport of non-Newtonian fluids in such context. Theoretical concepts related to fractured aquifer hydrogeology will be presented and addressed experimentally in the lab.