Joint estimates of permeability using complex resistivity and proton nuclear magnetic resonance

对地下水的流动进行建模，对于了解人类可利用的水量，以及碳等化学物质在地下、溪流和大气中的移动是至关重要的。准确的地下水模型需要了解影响水流的土壤和岩石的性质(即渗透性)。渗透率传统上是通过抽水、段塞或封隔器测试诱发地下水流来直接测量的；然而，这些方法可能受到测量体积小的限制，并且需要存在井。基于地球物理技术的间接渗透率估计受益于相对较短的测量时间，不需要流体提取，并且从地表进行非侵入性估计(或在井中进行微侵入性估计)。然而，基于单一地球物理方法的渗透率估计通常需要对岩石类型进行校准，并且不能用来确定准确确定渗透率所需的所有物理性质。这项研究致力于开发一种基于两种互补地球物理方法-复电阻率(CR)和核磁共振(NMR)-的协同耦合来估计渗透率的创新方法，旨在提供稳健和微创的流域尺度渗透率测定。拟议的研究将结合机理模型开发、实验室测量和现场测量来开发基于复电阻率和核磁共振参数的渗透率模型。该模型和测量将在克里斯蒂娜河流域进行测试，这是一个由美国国家科学基金会资助的临界区天文台(CRB-CZO)，其中地下水模型的准确性受到地下渗透率复杂空间变化的限制。这项研究是朝着发展核磁共振/CR联合测量的关键一步，以获得关于渗透率的空间密集信息，从而改善地下水流动的定量特征。

Modeling the flow of groundwater is fundamental for understanding the quantity of water available for human use, and the movement of chemicals, such as carbon, underground, into streams, and into the atmosphere. Accurate groundwater models require an understanding of the properties of soils and rocks that affect the flow of water (i.e. the permeability). Permeability is traditionally measured directly by inducing groundwater flow using pumping, slug, or packer tests; however, these methods can be limited by small measurement volumes and require the existence of wells. Indirect estimates of permeability based on geophysical techniques benefit from relatively short measurement times, do not require fluid extraction, and are non-invasive when made from the surface (or minimally invasive when made in a borehole). However, estimates of permeability based on a single geophysical method often require calibration for rock type, and cannot be used to determine all of the physical properties required to accurately determine permeability. This research focuses on developing an innovative method for estimating permeability based on the synergistic coupling of two complementary geophysical methods - complex resistivity (CR) and nuclear magnetic resonance (NMR) - aimed at providing a robust and minimally-invasive determination of permeability at the watershed scale.The proposed research will use a combination of mechanistic model development, laboratory measurements, and field measurements to develop a permeability model based on CR and NMR parameters. The model and measurements will be tested at the Christina River Basin, an NSF funded Critical Zone Observatory (CRB-CZO), in which the accuracy of groundwater models has been limited by complex spatial variation in subsurface permeability. This research represents a critical step towards the development of joint NMR/CR measurements to obtain spatially dense information about permeability that will improve the quantitative characterization of groundwater flow.