Probing diffusion dynamics during hydrate formation by high field NMR relaxometry and diffusometry

Abstract

High-field nuclear magnetic resonance (NMR) relaxometry and diffusometry along with magnetic resonance imaging were used to monitor phase transition molecular dynamics during hydrate formation occurring in water droplets dispersed in liquid cyclopentane. 1D T₂ relaxation measurements indicate the extent of hydrate formation as well as a reduction in water droplet size with progression of hydrate growth. MRI intensity maps and T₂ relaxation maps indicate spatially dependent hydrate formation rates due to the heterogeneity of the system. Spectrally resolved diffusion measurements indicate a reduction in the porosity of the hydrate agglomerate as the hydrate shell increases in thickness. A novel signal rise observed in two dimensional T₁-T₂ relaxation correlation experiments indicates complex diffusion dynamics due to coupling between regions with varying relaxation and diffusion. These results indicate the ability to monitor hydrate growth and phase transition molecular dynamics due to evolution of the porous hydrate agglomerate by means of high-field NMR.

Keywords: Diffusometry; Hydrate formation; Molecular dynamics; Relaxometry.