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Rice大学Jonathan Ajo-Franklin博士以及加州州立大学长滩分校Matthew W. Becker博士合作，共同研究复杂岩石裂缝网络中的流动通道，并获得了NSF EAR博士后奖学金。地下深处是一种重要且日益被利用的资源，在那里热水可以被提取为能源，碳可以被隔离。然而，这些策略需要对流体如何在地下深处流动有透彻的了解，而裂缝的存在（大多数深层岩石的共同特征）使情况变得复杂，这限制了我们预测这些深层岩层对流体提取或注入的反应的能力。这些裂缝经常形成相互连接的快速流动通道网络，可以集中地下流体的流动；然而，现有的测试方法限制了我们了解地下流体如何通过这些裂缝网络集中的能力。该项目的目的是进一步开发新的方法，旨在更好地理解复杂的、相互连接的岩石裂缝网络如何在整个地下引导流体流动。此外，该项目旨在让休斯顿独立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，通过建造一个高度便携的、动手操作的教育工具和配套的视频制作，可以很容易地分发到整个学区的教室。天然岩石裂缝只占深层地下水系统的很小一部分，但它们通过沿高传输裂缝（通常称为水力骨干）以渠化的方式集中流体来控制地下流动。本研究将利用完全耦合的流体力学建模方法来分析镜湖断裂岩石实验场地之前收集的数据，通过水力试验的时间尺度变化来研究这一水力骨干的形成和演化。本研究的结果将提供一个时间分析，表明该水力骨干不是静态的，而是一个动态结构，随着水力试验的时间尺度而变化，导致地下流动和输运发生显著变化。结合动态裂缝位移测量，本建议的工作首次使用多频振荡流动测试，在完全耦合的流体力学框架下，探索沿复杂裂缝网络的水力骨干流动浓度的动态性质。拟议的研究结果将提供一个框架，以改善裂缝流动和输送建模模拟，降低在裂缝性地下水系统中观察到的异常突破位置的风险。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.