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

点击翻译按钮获取中文摘要

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.