Permeability and Elastic Properties of Fractured Rock: Systematic Experimental Investigation and Model Development

裂隙岩石的渗透性和弹性特性：系统实验研究和模型开发

• 批准号: 1519706
• 负责人: Carl Renshaw
• 金额: $ 49.7万
• 依托单位: Dartmouth College
• 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: 2015-06-15 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1519706&HistoricalAwards=false
• 关键词: Permeability; Elastic; Properties; Fractured; Rock

Fractured-rock aquifers are an important water resource. Complex fracture distributions in most rocks make it difficult to characterize and understand groundwater flow in them. Cost-effective methods are needed to ensure sound decisions in groundwater management. Methods using well water levels and cross-hole tests to identify groundwater flow pathways are useful, but the resolution of maps based on these data alone depends on the number of wells, which is commonly inadequate due to financial and time constraints. In these cases, it is necessary to rely on additional data, particularly seismic velocities, to improve the mapping of subsurface flow pathways. This research will be the first systematic experimental study of the flow properties in well-characterized 3D fracture networks that will relate changes in seismic velocity to changes in permeability. This proposal builds on more than a decade of work using ice as a model for rock, which has shown that the basic processes controlling brittle failure of rocks and ice are similar. However, ice has distinct experimental advantages over rock. The proposed experiments and model development offer the opportunity to gain insights into the elastic properties and permeabilities of a broad range of fractured, crystalline natural (i.e., rocks) and synthetic materials. Thus, this research has applicability to many disciplines in materials science, engineering, and the geosciences. Identifying narrow, continuous high conductivity zones in fractured rock is a pressing challenge in hydrogeology. Hydraulic tomography (the inverse modelling of multiple cross-hole well tests) has shown increasing promise for this task, but the resolution of hydraulic tomography is sensitive to the number of boreholes and cross-hole tests, which are commonly too few. In these cases it is necessary to rely on additional data types, particularly geophysical surveys, to improve the resolution of the hydrogeological characterization. Combining hydraulic and geophysical data is most effective when the form of the relationship that links geophysical and hydrogeological parameters, particularly the relationship between seismic velocities and permeability, is known. Both permeability and seismic velocity depend on fracture density. This research examines these relationships to link seismic velocity to permeability. Specifically, using ice as a model material, this will be the first systematic experimental study of the flow properties of well-characterized 3D fracture networks designed to elucidate the relationship between changes in seismic velocity and changes in permeability in fractured geologic media. Despite the importance of fracture-induced changes in elastic properties and permeability, there are few systematic observations of the co-evolution of these properties during brittle deformation. Such data are critical for refining constitutive models linking hydrogeologic and geophysical parameters. The proposed research is a combination of laboratory measurements and mechanistic model development that serves as a necessary precursor to field applications designed to obtain spatially dense information about permeability that will improve the quantitative characterization of groundwater flow and transport.

裂隙岩石含水层是一种重要的水资源。大多数岩石中复杂的裂缝分布使得难以描述和理解其中的地下水流。 需要采用具有成本效益的方法，以确保地下水管理方面的正确决策。 利用井水位和跨孔测试来确定地下水流路径的方法是有用的，但仅根据这些数据绘制的地图的分辨率取决于威尔斯的数量，由于资金和时间的限制，这通常是不够的。 在这些情况下，有必要依靠额外的数据，特别是地震速度，以改善地下水流通道的绘图。 这项研究将是第一个系统的实验研究的流动特性，以及特征的三维裂缝网络，将地震速度的变化，渗透率的变化。 这项建议建立在十多年的工作，使用冰作为岩石的模型，这表明控制岩石和冰的脆性破坏的基本过程是相似的。 然而，冰比岩石具有明显的实验优势。 所提出的实验和模型开发提供了深入了解各种断裂的、结晶的天然（即，岩石）和合成材料。 因此，本研究对材料科学、工程和地球科学的许多学科具有适用性。 在裂隙岩石中识别狭窄、连续的高导带是水文地质学中的一个紧迫挑战。水力层析成像（多个跨孔井测试的逆模型）已显示出越来越多的承诺，这一任务，但水力层析成像的分辨率是敏感的钻孔和跨孔测试，这是通常太少的数量。 在这些情况下，有必要依靠额外的数据类型，特别是地球物理调查，以提高水文地质特征的分辨率。当地球物理参数和水文地质参数之间的关系形式，特别是地震速度和渗透率之间的关系已知时，结合水力和地球物理数据是最有效的。渗透率和地震速度都取决于裂缝密度。本研究探讨这些关系，地震速度的渗透率。 具体来说，使用冰作为模型材料，这将是第一个系统的实验研究的流动特性的良好的特征的三维裂缝网络，旨在阐明地震速度的变化和渗透率的变化之间的关系在断裂的地质介质。尽管在弹性性能和渗透率的变化的重要性，有一些系统的观察这些属性的共同演变过程中脆性变形。 这些数据对于改进将水文地质和地球物理参数联系起来的本构模型至关重要。拟议的研究是一个实验室测量和机械模型开发的组合，作为一个必要的先驱，旨在获得空间密集的信息渗透性，这将提高地下水流动和运输的定量表征现场应用。