Methane Hydrate Formation and Thermal Based Dissociation Behavior in Silica Glass Bead Porous Media

Abstract

Formation and thermal based dissociation of methane pore space hydrate has been studied at various initial hydrate saturations and heating rates utilizing a 1.3 cm 3 glass bead sample pack. Initial hydrate formation occurred rapidly after pressurization and proceeded at a higher rate for systems with the lower initial water saturation. Peak initial formation rates for 21%, 41%, and 60% initial water saturation was 4.3 × 10 –6, 1.44 × 10 –6, and 1.7 × 10 –6 mol/s, respectively. Three distinct stages of formation were observed for hydrate growth in porous media; a rapid initial formation regime determined by the enclathration reaction followed by a slow mass limited diffusion regime again followed by a second rapid and discrete formation period. Peak efficiency rates ranged from 74% to 81%. Experimental and numerical results showed slightly higher efficiency rates and maximum cumulative efficiency values for lower heating rate conditions. Lower heating rates produce a higher cumulative efficiency at the trade-off of less total hydrate being dissociated. Cumulative production efficiencies were greater for conditions of higher initial hydrate saturation, with values at 62% for 18% hydrate saturation and 72% for 50% hydrate saturation.