Collaborative Research: Hydrogeophysical Quantification of Hydraulic Conductivity from Electrical Measurements of the Effective Properties of Porous Media

我们将从复合电导率（sigma*）测量中进行水力电导率(K)的量化研究。我们将研究(1)博伊西水文地球物理研究基地（BHRS）的粗冲积沉积物，(2)更细的冰川融化沉积物。（sigma*）包含(a)互连孔体积，(b)互连孔表面积，(c)孔喉大小控制流量的信息。我们将探索低频电参数是否可以作为这些孔隙几何参数的替代品，用于基于渗透理论和毛细管模型的K预测。粒径分布较窄的土壤在理论上表现出与孔长尺度相关的低频极化峰。基于渗流理论的K预测模型利用特征长度尺度。我们的工作将利用（sigma*）测量给出的孔隙长度尺度，探索基于渗透类型理论的K预测的有效性。表现出宽粒度分布的土壤通常没有极化峰，而是在（sigma*）测量频率范围内表现出恒定的极化。基于毛细管模型的K预测模型依赖于管道水力半径的替代测量，通常是可测量的单位孔隙体积比表面积（Spor）。我们的研究将探索极化的大小是否也可以用来建立K预测的电模型。实验室研究将检查候选的岩石物理关系，将（sigma*）与有效孔隙半径和（Spor）的测量联系起来。我们将研究(1)（r-）孔半径关系，其中(r)是与（sigma*(w)）极化频率(w)峰值相关的松弛时间，以及(2)单频(sigma')-(Spor)关系。将推导一个用复杂表面电导率（（sigma*）冲浪(w)）解释（sigma*(w)）的理论框架，并通过与达西流动试验的比较来评估其预测能力。升级将在BHRS上进行研究。基于井眼（sigma*）剖面的水力导电性估计值将与多级段塞流测试的K估计值进行比较。反演（sigma*）数据集用于层析估计K的两种策略是：(1)假设平稳的K预测方程，将（sigma*）图像直接转换为K图像，以及(2)估计K分区的结构反演。这些策略将通过与kriging井内K测量和现有水力层析成像数据集估算的BHRS空间K分布进行比较来评估。在项目的第三年，将为博士生提供一个水文地球物理研讨会。我们还将在罗格斯-纽瓦克（R-N）校园发展水文地球物理学的荣誉学生本科生（HUG）研究经验。该计划与R-N荣誉学院合作，每学期将提供2-3个HUG奖学金。我们将有选择地针对北卡罗来纳校区独特的少数族裔群体。加快推进水文地球物理试验台建设。为进行这项研究而购买的设备将通过促进水文科学大学联合会的水文测量设施(HMF)-地球物理模块提供给水文界。

We will conduct research on quantification of hydraulic conductivity (K) from complex conductivity (sigma*) measurements. We will study (1) coarse alluvial deposits of the Boise Hydrogeophysical Research Site (BHRS), and (2) finer glacial melt deposits. The (sigma*) contains information on (a) the interconnected pore volume, (b) the interconnected pore surface area, and (c) the pore throat size controlling flow. We will explore whether low frequency electrical parameters can provide proxies of these pore geometrical parameters used in K prediction based on percolation theory, as well as capillary tube models. Soils with a narrow grain size distribution exhibit a low-frequency peak in polarization theoretically related to a pore length scale. Models for K prediction based on percolation theory utilize a characteristic length scale. Our work will explore the effectiveness of K prediction based on percolation type theory using the pore length scale given by (sigma*) measurements. Soils that exhibit a broad grain size distribution are typically devoid of a polarization peak and instead exhibit a constant polarization over the frequency range of (sigma*) measurements. Models for K prediction based on capillary tube models rely on a proxy measure of the hydraulic radius of tubes, usually the measurable specific surface area per unit pore volume (Spor). Our research will explore whether the magnitude of the polarization can also be used to develop electrical models of K prediction.Laboratory studies will examine candidate petrophysical relationships linking (sigma*) to measures of the effective pore radius and (Spor). We will examine (1) the (r-) pore radius relation, where (r) is a relaxation time related to the peak in frequency (w) of the (sigma*(w)) polarization, and (2) the single frequency (sigma')-(Spor) relation. A theoretical framework for interpretation of (sigma*(w)) in terms of a complex surface conductivity ((sigma*)surf(w)), will be derived and its predictive capability evaluated by comparison with Darcy flow tests. Upscaling will be examined at the BHRS. Hydraulic conductivity estimates based on borehole (sigma*) profiles will be compared with K estimates from multi-level slug tests. Two strategies for inverting (sigma*) datasets for tomographic estimates of K are: (1) direct conversion of (sigma*) images to K images assuming a stationary K prediction equation, and (2) a structural inversion whereby the K zonation is estimated. These strategies will be assessed via comparison with spatial K distribution at the BHRS estimated from kriging of borehole-based K measurements, and available hydraulic tomography datasets.A Hydrogeophysics Workshop will be offered to Ph.D. students during Yr 3 of this project. We will also develop Honors student UnderGraduate (HUG) research experiences in Hydrogeophysics on the Rutgers-Newark (R-N) campus. This initiative, run in collaboration with the R-N Honors College, will provide 2-3 HUG stipends per semester. We will selectively target the unique minority population of the R-N campus. We will also accelerate ongoing efforts to make the BHRS a test bed for hydrogeophysics. Equipment purchased to conduct this research will be made available to the hydrological community via the Hydrologic Measurement Facility (HMF)-Geophysics module of the Consortium of Universities for the Advancement of Hydrologic Science (CUAHSI).