CAREER: Understanding transport processes in fractured sedimentary rock through multi-frequency and multi-method investigations

深层沉积岩是一种重要且日益利用的资源，它提供了可以从中提取地下水、石油和天然气的储层，同样也提供了储存空间。有存款吗多余的水、废物或碳可以被隔离。然而，这些岩体中存在裂缝，这是大多数深部岩石的共同特征，使我们难以理解这些地层在开采或储存活动期间的行为。沉积岩中的裂缝可以提供快速流动通道，沿着该通道可以发生集中流动和可能的渠化流动。它们同样可以提供一个沿着的平面，流体可以快速地与周围的岩石接触并起反应。然而，我们理解突出的断裂面内的流动的能力是有限的，使用现有的测试方法。该项目的目的是：1）进一步开发用于理解裂缝流动过程的新测试方法; 2）评估这些测试方法对裂缝各种特征（例如，裂缝孔径可变性、裂缝刚度）;以及3）在已知会发生复杂裂缝流动的现场规模研究地点评估这些测试方法的真实世界性能。同样，该项目的一个更广泛的目标是更好地教育发展中的水文学家和广大公众了解岩石断裂的重要性及其对含水层流动和运输的影响。通过建立一个？可见骨折？通过物理模型，我们将制作一个教育工具，让学生和其他人看到和评估污染物通过复杂断裂面的运动。这种教育工具，沿着与其他地下水教育展览，将通过巡回"弹出式"科学展览，把动手水文地质学周围的农村community.Pore空间在沉积岩往往提供了水的存储空间的大部分，并可能是流体流量的主要贡献者体积显示在整个国家。然而，沉积岩中的裂缝使对这些岩体中流动和输运的理解大大复杂化。裂缝可以使运输途径相当复杂，通过沉积物孔隙空间的扩散流（即，原生孔隙度）、通过裂缝的集中且可能通道化的流动（即，次生孔隙度）以及这两个域之间的流体的伴随交换。了解这些过程中的每一个的影响是至关重要的，以改善预测污染物在这些含水层中的运输，因为它们控制的溶质运动通过含水层，溶质羽流的传播速度，以及溶质的能力交换和化学反应与寄主岩石。振荡水力测试--储层内的流体压力以设定频率呈正弦变化并记录压力响应--已被反复建议作为表征岩石裂缝的有用策略。然而，这种测试在实践中的应用，已经显示出意想不到的响应，其中测试的岩石裂缝似乎具有“频率依赖”的水力特性，这意味着复杂的流内的断裂面。引用Guiltinan和Becker（2015年）的话，这"表明视水力参数的周期依赖性是地层中非均匀流动和储存的结果。因此，定期水力测试可以提供一种手段来表征基岩裂缝和裂缝网络中的流沟。“这项建议将评估这一假设和其他假设的频率依赖性使用数值实验和现场规模的破碎岩石测试。通过数值试验，该项目将评估多频振荡水力试验区分裂隙沉积岩中不同流动过程的能力。在现场规模，将实施详细的振荡流测试-单独和同时进行气体注入实验-以评估在受控研究现场的流动通道和岩石-宿主岩石交换的贡献。使用振荡液压层析成像（OHT）成像，这在实验室规模上显示出显着的承诺，这项工作将首先评估的程度的非均质性和流动沟道内的裂缝平面。在此之后，将在注气后评估岩石断裂对OHT试验的响应变化。这种多频率抽水试验方法是一种强大的工具，用于表征流量，因为它将测量一系列时间尺度上的水文响应（从而测量水文过程）。

Deep sedimentary rocks represent an important and increasingly utilized resource, providing reservoirs from which groundwater, oil, and gas can be extracted, and similarly providing storage volumes in which ?banked? excess water, wastes, or carbon can be sequestered. However, the existence of fractures in these rock bodies, which are a common feature of most deep rocks, complicates our ability to understand how these formations will behave during either extraction or storage activities. Fractures in sedimentary rock can provide fast flow pathways along which focused and possibly channelized flow can occur. They can likewise provide a plane along which fluids can rapidly come into contact and react with surrounding rock. Our ability to understand flow within prominent fracture planes, however, is limited using existing testing methods. The purpose of this project is: 1) To further develop novel testing methods for understanding fracture flow processes; 2) To evaluate the sensitivity of these testing methods to various features of fractures (e.g., fracture aperture variability, fracture stiffness); and 3) To evaluate the real-world performance of these testing methods at a field-scale research site where complex fracture flow is known to occur. A broader goal of this project, similarly, is to better educate both developing hydrologists and the public at large about the importance of rock fractures and their impact on aquifer flow and transport. By building a ?visible fracture? physical model, we will produce an educational tool that allows students and others to see and assess the movement of contaminants through complex fracture planes. This educational tool, along with other groundwater educational exhibits, will be displayed across the state through a touring "pop-up" science exhibit that brings hands-on hydrogeology to the surrounding rural community.Pore spaces within sedimentary rock often provide the majority of storage space for water and may be the primary contributor by volume to fluid flow. However, fractures in sedimentary rock drastically complicate the understanding of flow and transport in these bodies. Fractures can make transport pathways quite complex, with a combination of diffuse flow through the sediment pore spaces (i.e., primary porosity), focused and possibly channelized flow through fractures (i.e. secondary porosity), and a concomitant exchange of fluids between these two domains. Understanding the impact of each of these processes is crucial for improving predictions of contaminant transport in these aquifers, as they control the rates of solute movement through the aquifer, the spreading of solute plumes, and the ability of solutes to exchange and react chemically with the host rock. Oscillatory hydraulic testing--in which fluid pressure within a reservoir is varied sinusoidally at a set frequency and pressure responses are recorded--has been suggested repeatedly as a useful strategy for characterizing rock fractures. Application of this testing in practice, however, has shown unexpected responses, in which a tested rock fracture appears to have "frequency dependent" hydraulic properties, implying complex flow within the fracture plane. To quote Guiltinan and Becker (2015) this "suggests that the period-dependency of apparent hydraulic parameters is a result of heterogeneous flow and storage in the formation. Thus, periodic hydraulic testing may provide a means to characterizing flow channeling in bedrock fractures and fracture networks." This proposal will assess this and other hypotheses for frequency dependence using numerical experiments and field-scale fractured rock testing. Through numerical experiments, the project will assess the ability of multi-frequency oscillatory hydraulic testing to distinguish between different flow processes in fractured sedimentary rock. At the field scale, detailed oscillatory flow testing will be implemented--alone and alongside gas injection experiments--to assess the contributions of flow channeling and fracture-host rock exchange at a controlled research site. Using oscillatory hydraulic tomography (OHT) imaging, which has shown significant promise at the laboratory scale, this work will first assess the degree of heterogeneity and flow channeling within a fracture plane. Following this, changes in the response of the rock fracture to OHT testing will be assessed after gas injection. This multi-frequency pumping test approach represents a powerful tool for characterizing flow in that it will measure hydrologic response (and thus, hydrologic processes) over a range of timescales.