Effect of gas hydrates on physical properties of permafrost

Permafrost stores large amounts of natural gas in free and hydrate (clathrate) forms. Intrapermafrost gas hydrates were revealed in frozen core samples recovered from test, exploration, and production wells in the Arctic oil and gas fields. Being similar to ice in many respects, gas hydrates can be mute for geophysical surveys. Meanwhile, laboratory experiments show that the presence of a gas hydrate component in pore moisture affects considerably some parameters of frozen sediments, as well as processes in evolving permafrost. Hydrate-bearing permafrost has a lower thermal conductivity and permeability but a higher geomechanic strength than hydrate-free frozen ground. Gas hydrates also influence some geophysical variables, such as electrical resistivity which becomes higher at higher hydrate contents. Accumulation of gas hydrates changes the relative percentages of pore moisture components (ice-hydrate-liquid water) in systems comprising ice, free gas, and gas hydrates, which has bearing on the physical properties of permafrost. The presence of gas hydrates increases the strength and resistivity of permafrost and, on the other hand, tends to reduce its permeability and the rates of heat and mass transfer.