Effect of NaCl on methane hydrate formation and dissociation in porous media

• Presence of NaCl inhibits the kinetics of CH4 hydrate formation in porous media.
• Diminishing thermodynamic driving force during hydrate formation was presented.
• Dissociation investigated using constant temperature thermal stimulation (297.2 K).
• NaCl containing system achieved slightly faster gas production.

In this study, we investigate the effect of NaCl (1.5 wt. % and 3.0 wt. % concentration) on methane hydrate formation and dissociation kinetics in the presence of porous media. It was found that hydrate formation was significantly slower in the presence of NaCl as compared to experiments conducted without the presence of salts despite subjected to a higher kinetic driving force, affirming the significant kinetic inhibition effect of NaCl on methane hydrate formation in porous media. We also observed that methane hydrate formation in water at overpressures of 1.5 MPa and 4.2 MPa resulted in the completion of hydrate formation kinetics within 100 h, which was significantly faster than that of salt containing systems that took more than 150 h to reach a plateau. To study the difference in methane hydrate dissociation, water at a temperature of 297.2 K was used to thermally stimulate the hydrate beds externally. The rate of gas produced was not significantly different between hydrates formed from water and NaCl solution, with NaCl system showing slightly faster dissociation kinetics.