Study of gas flow dynamics in porous and granular media with laser-polarized ¹²⁹Xe NMR

Abstract

This thesis presents Nuclear Magnetic Resonance (NMR) studies of gas flow dynamics in porous and granular media by using laser-polarized ¹²⁹Xe . Two different physical processes, the gas transport in porous rock cores and the mass exchanges between different phases in fluidized granular systems, were investigated and new experimental methods were designed to measure several important parameters characterizing the two systems. Methods for measuring the parameters had been either unavailable or significantly limited previously. The research involved modeling the gas flow in porous and granular media by relating the dynamics of spin magnetization to the interesting parameters, as well as correspondingly designing new measurement methods and verifying them on the laboratory test beds. We proposed a simple method to measure two important parameters of reservoir rocks, permeability and effective porosity, by probing the flow front of laser-polarized xenon gas inside the rock cores. The method was thoroughly tested on different categories of rocks with permeability values spanning two orders of magnitude, and the results were in agreement with those from the established techniques.

(cont.) The uniqueness in the work is that the fast method developed is capable of measuring the two parameters simultaneously on the same setup. Bubble-emulsion exchange and emulsion-adsorption exchange in a fluidized bed are two processes crucial to the efficiency of many chemical reactors working in bubbling regime. We used differences in T2 and chemical shift to contrast the three phases in the xenon spectra, and designed methods to measure the inter-phase exchange rates. The measured results of the bubble-emulsion and emulsion-adsorption exchange rates agreed well with predictions based on available theory. Our approach is the first to non-invasively probe natural bubbles in a three-dimensional bed, and to measure the exchange rate between the emulsion phase and multiple bubbles.