Freeze barrier enhanced depressurization of hydrate exploitation: An improved method for the permeability boundary of marine hydrates

The implementation of an artificial impermeable overlying boundary has been proven to enhance recovery efficiency and prevent methane leakage during marine natural gas hydrate extraction. However, traditional methods such as lurry, gel, or CO2 hydrate injection can cause irreversible damage to the marine ecosystem, and prevent effective recovery of the materials used. To overcome these drawbacks, this study proposes the construction of a frozen barrier in the overlying layer of marine gas hydrates, to suppress methane leakage, strengthen the overlying sediments, and prevent seawater intrusion. This approach avoids ecological damage, and ensures seabed strata resilience. Experimental results show that the critical temperature for frozen barrier formation is -3 ℃, this effectively prevents the infiltration of pore fluids under actual marine conditions. The effects of the barrier’s freezing temperature and range on the gas production rate are numerically analysed, and simulation results show that the presence of the frozen barrier enhances the depressurization effect, thereby increasing the production rate by 18.67 %. When the frozen barrier range is 60 m, the hydrate dissociation rate increases by 24.67 %, and cumulative gas production rises by 24.41 %.