Thermal conductivity of methane hydrate-bearing Ulleung Basin marine sediments: Laboratory testing and numerical evaluation

The thermal conductivity of gas hydrate-bearing sediments is a key parameter used to evaluate the heat transfer process relevant to phase transformation during gas hydrate production and to assess heat flux properties within the hydrate stability zone. Relatively few thermal conductivity values for in-situ hydrate-bearing sediments and laboratory hydrate-bearing sediments have been reported for under saturated conditions with vertical effective stress. In this study, we used sandy sediments obtained during the Ulleung Basin Gas Hydrate Expedition 2 (UBGH2) Expedition in Korea to synthesize methane hydrate-bearing sediments with saline pore fluid. The transient plane source method was implemented to measure the thermal conductivity of specimens with variable gas hydrate saturations. The measured thermal conductivity was ∼1.47 W/m/K and was independent of hydrate saturation. Results from additional tests of ice- and water-unsaturated sediments were also compared to our findings. Both geometric mean and 3D thermal network models corroborated the experimentally measured thermal conductivities assuming expected physical properties.