Abstract (eng)
Subsurface imaging of the Earth has been performed for decades to acquire a range of geophysical data to help form a better understanding of our subsurface environment. In particular, the need to find, and manage groundwater sources is of critical importance. Measuring hydrogeologic properties of water in unconsolidated aquifers can be difficult, especially in unsaturated conditions (the vadose zone). In this thesis, borehole nuclear magnetic resonance (borehole NMR) measurements were performed using a newly acquired DART probe, from the company Vista Clara, to analyze numerous hydrogeologic properties in unsaturated and saturated sediment-water mixtures and compare the results to a rock analyzer which is a laboratory machine. The aim of this thesis was to examine the effect of saturation level, and particle size on the hydrogeologic properties of the sediment, and compare all of them. A pipe which represented a borehole was filled with different types of sediments in unsaturated and saturated conditions, in order to measure various hydrogeologic properties of these mixtures, such as the transverse relaxation time (T2), pore-size distribution, estimates of hydraulic conductivity, and the water content. Then, the same sediment-water experiments at similar degrees of saturation were performed in a recently installed machine (rock analyzer) which performs NMR measurement, and measures T2, which is compared to the experimental data from the DART probe and the lab results from the rock analyzer. The sediments used in this research project were different types of gravel and sand which are the dominant materials in unconsolidated aquifers. It was found that the resulting hydrogeologic properties of different gravel/sand-water mixtures vary at different saturation levels, and the data from the DART probe and rock analyzer had different T2 despite the experiments having similar degrees of saturation.