Evaluation of Storage in Fractured-Rock Aquifer Systems

裂隙岩含水层系统储存评估

• 批准号: 0710941
• 负责人: Thomas Burbey
• 金额: --
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-01 至 2011-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0710941&HistoricalAwards=false
• 关键词: Evaluation; Storage; Fractured; Rock; Aquifer

Many important local and regional aquifers occur in fractured and faulted crystalline-rock systems. Effective porosity and related storage occur in primary and secondary fracture networks as well as the matrix block. Many hydraulic tests have been designed to quantify flow and permeability of the fractured system, but accurate quantification and distribution of storage and porosity have been elusive because measuring the compression of the fractures or matrix block under stressed conditions is difficult and costly. One device that has been highly effective for providing stress-strain relations for quantifying skeletal specific storage properties in unconsolidated pumped basins is the borehole pipe extensometer. We propose to install a pipe extensometer in a well characterized fractured and faulted crystalline-rock aquifer system that is known to contain a major fracture zone from thrust faulting and a secondary fracture network contained within a low permeability matrix. The extensometer design will allow for accurate strain measurements for a rock (and fracture) compressibility of 10-1l m2/N. Residual strains from earth tides, barometric and rainfall loading and temperature effects can be monitored and effectively eliminated. Designed cyclical hydraulic tests will yield hysteretic stress-strain curves leading to quantification of primary and secondary fracture compressive storage properties. Analytical modeling of flow verses time using the heatpulse flow meter and type-curve analysis can provide estimates of fracture transmissivity and total fracture storage. The coupled extensometer and analytical modeling analysis can allow for quantification of porosity and block hydraulic conductivity along with accurate storage estimates. Finite-element modeling with ABAQUS allows for the use of transient parameters in a dual permeability/porosity system that will provide further understanding of the hydraulic characteristics and response under stressed conditions.The broader impacts of this proposed research are significant because storage and porosity quantification in fractured rocks is often elusive, even with detailed and costly aquifer testing techniques. The combined use of extensometer data coupled with analytical and numerical modeling will provide detailed estimates of all important hydraulic properties of fractures. The techniques used and developed in this research can be readily applied to all fractured-rock settings. This would represent the first and only operating pipe extensometer in the eastern United States (the only one in the country in fractured crystalline rocks) and would provide important data and opportunities for researchers and students from other universities and the US Geological Survey who would not otherwise have access to this device or the strain measurements it will yield. The data obtained from the extensometer will be incorporated into two hydrogeology courses at Virginia Tech as part of lectures pertaining to strain, storage, and fracture mechanics. It will also be available for student field trips to the Fractured Rock Research site that we are continuing to develop in the Blue Ridge province.

许多重要的地方和区域含水层出现在断裂和断层的结晶岩石系统中。有效孔隙度和相关储存发生在原生和次生裂缝网络以及基质块中。许多水力试验旨在量化裂缝系统的流量和渗透率，但储量和孔隙度的准确量化和分布一直难以实现，因为测量应力条件下裂缝或基质块的压缩既困难又昂贵。钻孔管道引伸计是一种非常有效的设备，可以提供应力-应变关系，以量化松散抽水盆地中骨骼的特定存储特性。我们建议在特征良好的裂缝和断层结晶岩石含水层系统中安装管道引伸计，该系统已知包含逆冲断层造成的主要裂缝区域和低渗透性基质中包含的次生裂缝网络。引伸计设计可对 10-1l m2/N 的岩石（和裂缝）压缩率进行精确应变测量。可以监测并有效消除来自地球潮汐、气压和降雨载荷以及温度影响的残余应变。设计的循环水力试验将产生滞后应力-应变曲线，从而量化初级和次级裂缝压缩存储特性。使用热脉冲流量计和类型曲线分析对流量与时间的关系进行分析建模，可以提供裂缝透射率和总裂缝储存量的估计。耦合的引伸计和分析模型分析可以量化孔隙度和块体导水率以及准确的存储估计。 ABAQUS 有限元建模允许在双渗透率/孔隙度系统中使用瞬态参数，这将有助于进一步了解压力条件下的水力特性和响应。这项研究的更广泛影响是重大的，因为即使采用详细且昂贵的含水层测试技术，裂隙岩石中的存储和孔隙度量化通常也难以捉摸。引伸计数据与分析和数值建模的结合使用将为裂缝的所有重要水力特性提供详细的估计。本研究中使用和开发的技术可以轻松应用于所有裂隙岩石环境。这将代表美国东部第一个也是唯一一个运行的管道引伸计（该国唯一一个在裂隙结晶岩中使用的管道引伸计），并将为其他大学和美国地质调查局的研究人员和学生提供重要的数据和机会，否则他们将无法使用该设备或其产生的应变测量结果。从引伸计获得的数据将被纳入弗吉尼亚理工大学的两门水文地质学课程中，作为有关应变、存储和断裂力学的讲座的一部分。它还可供学生实地考察我们正在蓝岭省继续开发的断裂岩石研究站点。