Raman spectroscopic and kinetic analysis of hydrate shell formation on hydrogel particles containing monoethylene glycol

Abstract

Hydrate shell growth on hydrogel particles incorporating monoethylene glycol (MEG) was investigated using Raman spectroscopy and a high pressure autoclave apparatus. Surface images of hydrogel particles covered by a hydrate shell are presented and the obtained Raman spectra indicate MEG molecules were excluded from the formation of the hydrate shell. The Raman spectra and surface imaging of the particles demonstrate that the particles remain intact after the dissociation of the shell. In subsequent hydrate formation cycles, the hydrate fraction in the liquid phase was determined from gas consumption measurements in a high pressure autoclave. The hydrate fraction reached only 0.11 for hydrogels containing MEG while a high hydrate fraction of 0.41 was observed for a control system consisting of bulk water and decane mixture. The growth rate in the presence of hydrogel particles was suppressed in the early stages of hydrate formation, suggesting that the increasing MEG concentration inside the hydrogel core may limit the further inward hydrate growth. After hydrate formation the hydrogel particles were analyzed by thermogravimetric analysis (TGA), suggesting the possibility of recovering hydrogel polymer through conventional heating methodologies. These results demonstrate that injecting hydrogel particles containing high concentration of MEG may be feasible to manage the risk of hydrate plug formation as they will absorb the free water resulting in the dispersed hydrogel particles among the hydrocarbon liquid phase.