Thermal Stabilities of CH4 and CO2 Hydrates in Quartz Sands and Modeling

Forming an impermeable hydrate bearing layer is a novel path to prevent CO2 leakage during marine carbon storage. To make an accurate description of the formation of impermeable hydrate bearing layer, the equilibria of CH4 and CO2 hydrates in quartz sands were measured in a temperature range from 273 to 283 K using isochoric pressure search method and HP-μDSC. The influence of particle size from 0.025 to 0.3 mm and water saturation from 5 to 30% on the hydrate equilibrium were analyzed. Based on the typical hydrate equilibrium model, van Genuchten model was employed to describe the capillary effect. Results showed that particle size had negligible effect on the equilibria of CH4 and CO2 hydrates, but a decrease in water saturation was found to lead an exponential growth in temperature depression. As the water saturation reduced down to 10% and below, the temperature depression surged from about 0.1 up to 0.89 K in maximum. The dissociation enthalpies of CH4 and CO2 hydrates were determined as 56.01 ±1.29 and 64.98 ± 1.90 kJ/mol respectively. The reduction of water saturation from 30 to 5% was found to enhance the dissociation enthalpy for CH4 hydrate, but no similar effect was observed for CO2 hydrate.