Using horizontal and vertical deformation signals to characterize water availability in fractured and faulted crystalline-rock aquifer systems

使用水平和垂直变形信号来表征裂缝和断层结晶岩石含水层系统中的水可用性

• 批准号: 1446200
• 负责人: Thomas Burbey
• 金额: $ 27.03万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-03-01 至 2020-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1446200&HistoricalAwards=false
• 关键词: Using; horizontal; vertical; deformation; signals

A large portion of the world's potable groundwater occurs in fractured bedrock, and these aquifers are difficult to characterize for how much water is available and how easily accessible it is. The ability to secure sustainable and significant quantities of potable groundwater from fractured and faulted crystalline-rock environments requires novel non-invasive ways to characterize these complex aquifers. Successful characterization depends upon accurate estimates of the parameters that govern flow, recharge, and storage capacity. Most fracture characterization relies on measurements of water levels or pressure changes in wells which have been shown to be inadequate for accurately estimating aquifer properties. This project will measure vertical and horizontal rock deformation signals at the land surface and within the borehole that result from pumping-induced stresses. This project will demonstrate the use of these data for characterizing local and regional fractured aquifers and for quantifying parameters that support assessment water recharge and flow in these systems. The results of this research will improve the estimation of the quantity of water that can be safely extracted from fractured rock aquifers. The investigation is focused on sites in Ploemeur, France, and in Virginia, USA, that will establish a collaboration between the University of Rennes and Virginia Tech that affords graduate students the opportunity to study abroad and broaden their research perspectives and international exposure.The research will invoke surface horizontal and vertical deformation signals at different temporal and spatial scales to inversely calibrate a 3D coupled poromechanical and flow model to accurately estimate fracture and host rock properties (transmissivity and storage) and flow geometries (fracture or fault orientation and root depth). A local and a sub-regional flow system in the crystalline rocks near Ploemeur will be studied. Two distinct horizontal deformation signals exist there: a seasonal signal showing deformation associated with a gently dipping horizontal contact zone and a converging deformation signal oriented along strike of a sub-vertical fracture zone associated with a 2-day aquifer test. The Ploemeur site will be used to show how vertical deformation signals with seasonal water-level changes can be used to accurately quantify groundwater recharge. The research will develop a new analytical aquifer testing tool to estimate stress-dependent parameters based on data collected at the fractured rock site in Virginia. The results of this research improve upon traditional fracture tests using forced-gradient packer tests that have been shown not to work because the measured water-level and fracture strain are stress dependent.

世界上很大一部分可饮用地下水存在于断裂基岩中，这些含水层很难描述有多少水可用以及如何容易获得。从断裂和断层结晶岩环境中获得可持续和大量饮用地下水的能力需要新的非侵入性方法来表征这些复杂的含水层。成功的表征取决于对控制流量、补给和存储容量的参数的准确估计。大多数裂缝表征依赖于威尔斯井中水位或压力变化的测量，这已被证明不足以准确估计含水层特性。该项目将测量地面和钻孔内由泵激应力引起的垂直和水平岩石变形信号。该项目将展示如何利用这些数据来描述当地和区域裂隙含水层的特征，并量化支持评估这些系统中的水补给和流量的参数。这项研究的结果将改善水的数量，可以安全地从破碎的岩石含水层提取的估计。调查的重点是法国普洛默和美国弗吉尼亚州的遗址，这将建立雷恩大学和弗吉尼亚理工大学之间的合作，为研究生提供出国留学的机会，拓宽他们的研究视野和国际曝光。该研究将调用不同时间和空间尺度的地表水平和垂直变形信号，以反向校准3D耦合孔隙力学和流动模型，以准确地估计裂缝和寄主岩石性质（渗透和储存）和流动几何形状（裂缝或断层方向和根部深度）。将研究普洛默附近结晶岩中的局部和次区域流动系统。 那里存在两种不同的水平变形信号：显示与缓倾水平接触区相关的变形的季节性信号和与2天含水层测试相关的沿着近垂直断裂带走向定向的会聚变形信号。Ploemeur站点将用于展示如何使用季节性水位变化的垂直变形信号来准确量化地下水补给。该研究将开发一种新的分析含水层测试工具，以根据在弗吉尼亚州断裂岩石现场收集的数据估计应力相关参数。这项研究的结果改进了传统的压裂测试，使用强制梯度封隔器测试，已被证明不工作，因为测得的水位和断裂应变是应力相关的。