FRACTURED AQUIFER CHARACTERIZATION USING SMART NON-NEWTONIAN TRACERS

题目：使用智能非牛顿示踪表征裂缝含水层研究者：John S. Selker，俄勒冈州立大学提案号：EAR 1446915裂缝岩石含水层是美国许多地区和世界其他地区唯一的水源。了解这些水，以及水所运输的物质，对于提供和保护安全的饮用水至关重要。此外，水流裂隙岩在矿床的形成和深部地热系统的发育中起着重要作用。这项研究也将有利于从裂缝性储层中提取石油和天然气，包括那些由水力压裂产生的储层。因此，这项研究既是理论性的，也是潜在的实践性的。能够识别裂缝中流体流动路径的方法非常有限。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深入了解裂缝性岩石含水层和其他裂缝性岩石系统的流动情况。在实验室工作的同时，将在法国Ploemeur的观测站进行现场实验，在那里建立了一个独特的断裂流场场地，专门用于这种实验。此外，两名本科生将参与研究。裂缝岩石中主导流道的识别、连通性及其水力特性对流体流动和溶质运移至关重要。从实验室到现场，示踪测试都可以描述这种含水层的特性。经典示踪剂测试解释允许根据简化的输运模型定义平均“有效水力”孔径。本研究将：1)开发一种创新的示踪剂方法，使用非牛顿流体（“剪切变薄”）来识别天然裂缝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，了解它们的流变学，以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孔径大小，而较小的孔径将基本上“冻结”在凝胶填充的条件下。这将在实验室和仪器现场进行测试，以证明其在表征含水层特性方面的效用。剪切减薄流体在实际岩石孔隙中运动的实验观测结果将与流体输运的理论模型进行比较。此外，数值模拟将探索由实验方法确定的假设(例如，稳定（非牛顿流体驱替）vs不稳定（水驱替非牛顿流体驱替）。在初步结果的基础上，现场实验方法将验证所提出方法的有效性。在示踪剂测试期间，将使用耦合时移探地雷达测量，以记录示踪剂采取的优先路径。该方法将在法国一个独特的、特征良好的裂缝花岗岩地层中进行测试，该地层已经根据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输运的一阶参数的敏感性。与裂缝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.