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

我们将开展从复电导率(Sigma*)测量中量化水力电导率(K)的研究。我们将研究(1)博伊西水文地球物理研究场(BHRS)的粗冲积物，以及(2)较细的冰川融化沉积。(sigma*)包含关于(A)相互关联的孔隙体积、(B)相互关联的孔隙表面积和(C)控制流动的孔喉尺寸的信息。我们将探索低频电性参数是否可以提供这些孔隙几何参数的替代物，用于基于渗流理论的K预测以及毛细管模型。粒度分布较窄的土壤在理论上表现出与孔隙长度尺度相关的极化低频峰值。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*)测量给出的孔长标度来探索基于渗流类型理论的K预测的有效性。表现出广泛的粒度分布的土壤通常没有极化峰，而是在(sigma*)测量的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，通常是单位孔体积的可测量比表面积(Spor)。我们的研究将探索极化的大小是否也可以用来开发K预测的电学模型。实验室研究将检验候选岩石物理关系(sigma*)与有效孔隙半径和(Spor)的测量。我们将研究(1)(r-)孔半径关系，其中(R)是与(sigma*(W))极化的频率峰值(W)有关的驰豫时间，以及(2)单频(sigma‘)-(Spor)关系。将推导出用复杂表面电导率((sigma*)SURF(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进行审查。基于井眼(Sigma*)剖面的水力传导性估计将与从多水平段塞试验中估计的K进行比较。用于层析成像估计K的(Sigma*)数据集的两种策略是：(1)假设固定的K预测方程，将(Sigma*)图像直接转换为K图像；(2)构造反转，由此估计K分带。这些策略将通过与基于钻孔的K测量值的克里格法估计的BHRS的空间K分布和现有的水力层析成像数据进行比较来评估。在本项目的第三年期间，将向博士生提供水文地球物理研讨会。我们还将在罗格斯-纽瓦克(R-N)校区发展水文地球物理方面的优等生本科生(HUG)研究经验。这项计划与R-N荣誉学院合作，每学期将提供2-3次拥抱津贴。我们将有选择地瞄准R-N校区独特的少数族裔人群。我们还将加快正在进行的努力，使BHRS成为水文地球物理的试验台。为开展这项研究而购买的设备将通过大学水文科学促进联盟(CUAHSI)的水文测量设施(HMF)--地球物理学模块提供给水文界。

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).