EAR-PF: Dynamic flow channeling through complex fracture networks under multi-frequency oscillatory flow conditions: A fully-coupled hydromechanical approach

Jeremy R.Patterson博士与加州州立大学长滩分校的Matthew W.Becker博士合作，获得了美国国家科学基金会EAR博士后奖学金，与Jonathan Ajo-Franklin博士在莱斯大学研究复杂岩石裂隙网络中的水流导流。深层地下是一种重要的、越来越多地被利用的资源，在那里可以提取热水作为能源，并可以隔离碳。然而，这些策略需要彻底了解流体如何通过深层地下流动，而裂缝的存在使这一点变得复杂--这是大多数深层岩石的常见特征--限制了我们预测这些深层岩层在流体提取或注入时的行为的能力。这些裂缝经常形成相互连接的快速流动路径网络，可以集中地下流体流动；然而，现有的测试方法限制了我们了解地下流动如何通过这些裂隙网络集中的能力。该项目的目的是进一步开发新的方法，旨在更好地了解复杂的、相互关联的岩石裂隙网络如何引导整个地下的流体流动。此外，该项目旨在让休斯顿独立学区(少数民族占多数的学区)的学生了解地下水资源的重要性以及裂缝对地下水流动的影响，方法是制作一种高度便携的动手教育工具和配套的视频制作，可以很容易地分发到整个校区的教室。天然岩石裂缝只占深层地下水系统的一小部分，但它们通过沿高传导性裂缝(通常被称为水力主干)以沟道化的方式集中流体来控制地下水流。这项提案将使用完全耦合的流体力学建模方法来分析镜湖裂隙岩实验场先前收集的数据，以随水力试验时间尺度的变化来研究这种水力骨干的形成和演化。这项研究的结果将提供时间分析，表明这种水力骨干不是静态的，而是随着水力试验的时间尺度而变化的动态结构，导致地下水流和输运的显著变化。与动态裂缝位移测量相结合，本研究首次采用多频振荡水流试验，探索在完全耦合的流体力学框架下，水力骨干上复杂裂隙网络中水流集中的动态性质。拟议的研究结果将提供一个框架，改进裂隙流动和运移模拟，降低在裂隙地下水系统中观察到的异常突破位置的风险。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Dr. Jeremy R. Patterson has been awarded an NSF EAR Postdoctoral Fellowship to research flow channeling through complex rock fracture networks at Rice University with Dr. Jonathan Ajo-Franklin in collaboration with Dr. Matthew W. Becker at California State University – Long Beach. The deep subsurface represents an important and increasingly utilized resource where hot water can be extracted for energy and carbon can be sequestered. However, these strategies require a thorough knowledge of how fluids move through the deep subsurface, which is complicated by the presence of fractures – a common feature in most deep rocks –limiting our ability to predict the behavior of these deep rock formations in response to fluid extraction or injection. These fractures frequently form inter-connected networks of fast flow pathways that can focus subsurface fluid flows; however, existing testing methods limit our ability to understand how subsurface flows are concentrated through these networks of fractures. The purpose of this project is to further develop new methods aimed at better understanding how complex, inter-connected networks of rock fractures channelize fluid flow throughout the subsurface. Further, this project seeks to expose students in the Houston Independent School District, a majority-minority school district, to the importance of groundwater resources and the impact of fractures on groundwater flows through the building of a highly portable, hands-on educational tool and companion video production that can be easily distributed to classrooms throughout the school district.Natural rock fractures comprise a very small fraction of deep groundwater systems, yet they dominate subsurface flows by concentrating fluids in a channelized manner along highly transmissive fractures, commonly referred to as a hydraulic backbone. This proposal will investigate the formation and evolution of this hydraulic backbone with variations in the temporal scale of hydraulic testing using a fully-coupled, hydromechanical modeling approach to analyze previously collected data at Mirror Lake Fractured Rock Experimental Site. The results of this research will provide a temporal analysis that shows this hydraulic backbone is not a static, but rather a dynamic structure that changes with the timescale of hydraulic testing, resulting in significant changes to subsurface flow and transport. Combined with dynamic fracture displacement measurements, the work in this proposal represents the first use of multi-frequency oscillatory flow testing to explore the dynamic nature of flow concentration along a hydraulic backbone through complex fracture networks under a fully-coupled hydromechanical framework. The results of the proposed research will provide a framework that improves fracture flow and transport modeling simulations, reducing the risk of anomalous breakthrough locations observed in fractured groundwater systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.