Experimental results on hydrate and ice formation conditions in the pores of sandy sediments during temperature cycles are presented. To better understand how hydrate accumulates in sandy sediments, we measured the accumulation of CH4 and CO2 hydrate and ice in sandy sediments under various conditions. With the pressure above that needed for hydrate formation, cycling the temperature below and above the freezing point of water increased the amount of hydrate in the sediments. The self-preservation effect allowed us to determine the structure and some physical properties of these sediments that contained ice and hydrate.
Frozen sediments exist on polar shelves under seawater. Such sediments occur in various areas of the Arctic shelf including areas in the Barents Sea, Kara Sea, Laptev Sea, and Beaufort Sea (Romanovskii, 1993). Measurements, aided by calculations, show that their thicknesses are tens to hundreds of meters. Geophysical data, including gas emissions during drilling, out gassing of cores, and gas fountains indicate that such sediment includes gas hydrates (Ginsburg and Soloviev, 1998; Melnikov and Spesivzev, 1995; Collett and Dallimore, 2000). Geological studies and thermal modeling of undersea conditions indicate that ice and gas hydrates can form in sediments when the environmental temperature is lowered. The existence of sediment regions containing ice and gas hydrates on a polar shelf significantly complicate the exploration of large gas deposits, which was discovered not long ago on a polar ice shelf. For such explorations, research on the formation, existence, and properties of frozen gas hydrates in sediments is needed. In particular, laboratory experiments on gas hydrates and ice formation in sediments is necessary. There have been recent experiments on hydrate formation in sediments. Such experiments have shown that the conditions of gas hydrate formation in the pores of sediments differ from those without sediments.