Gas Permeability of Sandy Sediments: Effects of Phase Changes in Pore Ice and Gas Hydrates

The gas permeability of sandy porous sediments is studied in freezing/thawing and pore gas hydrate formation/dissociation experiments using a specially designed system. The permeability of sandy soil to gas is controlled by phase changes of the pore water components (water, ice, or gas hydrate) depending on temperature and pressure. The gas permeability of the sand samples decreases upon freezing and during the formation of pore gas hydrates but increases when pore gas hydrates dissociate upon pressure drop to below-equilibrium values. The magnitude of permeability decrease and increase varies as a function of the initial water–ice saturation and the pore space structure. Clay contents and mineralogy affect the behavior of gas permeability in frozen and thawed sand samples containing a clay component. The experimental results can have multiple uses: modeling and testing of economically feasible techniques for gas production from permafrost Arctic reservoirs, including hydrate-bearing sediments, or mapping of permeable zones for tracing methane emission in high latitudes.