The impact of porous microstructures of gas hydrates on their macroscopic properties

Methane hydrates front both sub-permafrost and seafloor occurrences show a very particular microstructure as evidenced by scanning electron microscopy. These hydrates are frequently porous. with typical pore sizes ranging front 100 not to 500 nor and occasionally reaching 1 mum. The pores are predominantly. closed with only occasional openings between them. and they are filled with methane gas. The gas-filling will affect the physical properties of gas hydrates. In particular. an increase in the attenuation of elastic waves can be expected. We suggest that the repeatedly observed combination of high seismic velocities and high attenuation in gas hydrate-bearing sediments may well be attributed to the presence of gas in the porous microstructures.