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Permafrost composed of sand with silt and clay components may store stable and metastable gas hydrates, which can lose stability under a flux of dissolved salts from natural or production-related solutions (seawater, brines from cryopegs, drilling fluids, etc.). The flux of salt ions is controlled externally by temperature and pressure as well as by the salinity of solutions and the properties of fine-grained (<0.05 mm) components in permafrost. The effect of silt and clay percentage and mineralogy (kaolinite or montmorillonite) on the patterns of salt and water transport and the related dissociation of pore gas hydrates in frozen sand is studied in laboratory experiments. The experiments are conducted in conditions that can maintain the self-preservation of gas hydrates: a constant negative temperature of −6 °C and a pressure of 0.1 MPa. Sediments with higher clay percentages show slower migration and accumulation of salt ions and the higher critical salt concentration required for the onset of gas hydrate dissociation. The flux of Na+to sand samples containing montmorillonite is lower than to those with kaolinite. On the other hand, salt migration and hydrate dissociation are faster in sand with higher silt contents. The experimental results form the basis for a generalized model of main mechanisms that drive salt transport in frozen hydrate-bearing sediments interacting with saline solutions.

Development of the Arctic region faces many problems, including methane emission from permafrost. Among other causes, methane emission may result from destabilization and dissociation of intrapermafrost gas hydrates under temperature and pressure changes or chemical reactions. The effects of the temperature and pressure on the stability of intrapermafrost gas hydrates have been quite well-studied, but the chemical effects, such as migration of salts, remain poorly understood. In this study, the interaction of frozen hydrate-saturated sediments with NaCl solutions is simulated in physical experiments at different gas pressures from 0.1 to 4.0 MPa and at a constant negative temperature of around −6.0 °C. The experiments show that the external pressure significantly affects the migration of Na+into frozen hydrate-bearing sand: salt transport accelerates at lower pressures, while pore hydrates lose stability. However, the effect of the pressure on frozen hydrate-free sediments is minor. The experimental results make a basis for a model of pore space changes in frozen hydrate-saturated rocks interacting with salt water under gas pressures above or below the equilibrium value.