Microscopic experimental study on the effects of NaCl concentration on the self-preservation effect of methane hydrates under 268.15 K

• Increasing NaCl concentration accelerates the initial dissociation rate of methane hydrates at 268.15 K, with negligible self-preservation observed at 3.35% NaCl and in seawater systems. • In situ Raman spectroscopy and confocal microscopy reveal that hydrate dissociation below the ice point proceeds via intermediate liquid water before ice formation, not directly to solid ice. • Salt ions disrupt the water-to-ice transition, thereby weakening the self-preservation effect of methane hydrates. • These findings inform strategies for gas storage/transport and natural gas hydrate exploitation, highlighting the need to account for salinity in self-preservation applications.