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

职业：通过多频率和多方法研究了解裂隙沉积岩中的传输过程

基本信息

批准号：
1654649
负责人：
Michael Cardiff
金额：
$ 250万
依托单位：
University of Wisconsin-Madison
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-06-01 至 2023-05-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1654649&HistoricalAwards=false
关键词：
CAREER Understanding transport processes fractured

项目摘要

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.

深层沉积岩代表了一种重要且越来越多的资源，提供了可以从中提取地下水，石油和天然气的水库，并提供类似的储存量？多余的水，废物或碳可以隔离。但是，这些岩石物体中裂缝的存在，这是大多数深岩石的常见特征，使我们了解这些形成在提取或储存活动中的表现的能力使我们变得复杂。沉积岩中的断裂可以提供沿着聚焦和可能引导流动的快速流道。它们同样可以提供沿着流体可以迅速接触并与周围岩石反应的平面。但是，使用现有的测试方法，我们了解突出裂缝平面内流动的能力受到限制。该项目的目的是：1）进一步开发新的测试方法来理解断裂流动过程； 2）评估这些测试方法对裂缝特征的敏感性（例如，骨折孔径变异性，断裂刚度）； 3）在现场尺度研究地点评估这些测试方法的现实性能，该研究位点已知发生复杂的断裂流。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公众对岩石断裂的重要性及其对含水层流和运输的影响。通过建立可见的裂缝？物理模型，我们将生产一种教育工具，使学生和其他人可以通过复杂的裂缝平面看到和评估污染物的运动。该教育工具以及其他地下水教育展览会将通过巡回演出的“弹出”科学展览展出，该展览将动手的水文地质学带到周围的农村社区。沉积岩石内的储藏空间通常为水的大部分存储空间提供水，并且可能是由流体流动的主要贡献。然而，沉积岩中的断裂使对这些身体的流动和运输的理解非常复杂。裂缝可以使运输途径非常复杂，并结合了通过沉积物孔隙空间（即初级孔隙率），聚焦和可能通过断裂（即次要孔隙率）引导的流动的流动，并在这两个域之间进行流体交换。了解每个过程的影响对于改善这些含水层中污染物转运的预测至关重要，因为它们控制了通过含水层的溶质运动速率，溶质羽流的扩散以及溶质与宿主岩石进行化学反应和反应的能力。振荡性液压测试 - 在储层内哪种流体压力在设定的频率下会变化，并记录压力响应 - 被反复建议作为表征岩石裂缝的有用策略。然而，在实践中的应用显示出意外的响应，其中测试的岩石断裂似乎具有“频率依赖”的液压特性，这意味着裂缝平面内的复杂流动。引用Guiltinan and Becker（2015）的话，“这表明明显的液压参数的周期依赖性是形成中异质流和存储的结果。因此，定期液压测试可能提供了表征床上骨折骨折和骨折网络中流动通道的手段。”该提案将使用数值实验和野外刻度断裂的岩石测试来评估这一建议和其他假设，以实现频率依赖性。通过数值实验，该项目将评估多频振荡液压测试区分裂缝沉积岩石中不同流动过程的能力。在现场尺度上，将在受控研究地点评估流量通道和断裂 - 宿主岩石交换的贡献，将实施详细的振荡流测试。使用振荡性液压断层扫描（OHT）成像，该成像在实验室尺度上显示出很大的希望，这项工作将首先评估裂缝平面内的异质性和流动通道的程度。此后，将在注射气体后评估岩石裂缝对OHT测试的反应变化。这种多频抽水测试方法代表了表征流动的强大工具，因为它将在一系列时间尺度上测量水文响应（以及水文过程）。