The thermal conductivity of artificial methane hydrate sediment was measured at atmospheric and also at the higher-pressure conditions, which imitates the actual hydrate sediment area under seabed. The hydrate powder for this experiment was synthesized by solid-liquid interface method at the condition of 268.15K, 8.0MPa. Synthesized hydrate powder was mixed with "Toyoura Standard Sand " and compressed to make artificial hydrate sediment pellet. Thermal conductivities of hydrate pellets were measured by hot disc transient method. Relationship between thermal conductivity of hydrate sample and sample properties (gas content, mixing ratio with sand) was investigated with some mixing models such as series model, parallel model and distribution model. Distribution model showed the best agreement with our measured values. However, it seems depend on the structure of hydrate sediment. To evaluate applicability of mixing models to real field, it is important to get the detailed information of structure on the naturally occurring real hydrate sediment.
Gas hydrate is a clathrate compound that is composed of guest gas molecules and host water molecules. Recently, it becomes well known that there are large amount of methane hydrate (MH) in the sediment under the seabed as same as land areas of permafrost regions. It estimated to exist enormously in the sediment under the sea bottom near Japan. Since this MH contains large quantity of methane gas, it became considered as one of the substantial future energy resources. Thus, the project to recover it from the sea bottom near Japan was Launched. Thermal properties such as thermal conductivity (λ), heat of dissociation (ΔH) and heat capacity (Cp) of MH sediment are very important to evaluate economy of the gas hydrate production. However, there is not sufficient experimental data on those thermal properties. Especially, very few data is reported for thermal.
