This paper presents the measurement of the thermal constants of natural methane hydrate-bearing sediments and mud layer samples recovered from wells. Core samples were recovered from the Tokai-oki test wells (Nankai Trough, Japan) in 2004. The thermal conductivity, thermal diffusivity, and specific heat of the samples were simultaneously determined using the hot-disk transient method. The thermal conductivity of natural hydrate-bearing sediments decreased slightly with increasing porosity. In addition, the thermal diffusivity of hydrate-bearing sediments decreased as the porosity increased. Moreover, we also used simple models to calculate the thermal conductivity and diffusivity. Estimations of the distribution model (geometric mean model) were relatively consistent with the measured results, suggesting that sand grains and hydrates should be independently distributed for hydrate-bearing sediments, which exhibit a pore-filling pattern. The measurement results were also consistent with the thermal diffusivity, which was estimated by dividing the thermal conductivity obtained from the distribution model by the specific heat taken from the arithmetic mean. Finally, our estimate of the thermal conductivity of silt soil was much lower than that for sand soil in hydrate-bearing sediment, which suggests that the small grains influence thermal conductivity.

We study the formation of tetrahydrofuran (THF) clathrate hydrate from polyvinylpyrrolidone (PVP) aqueous solution as a function of growth rate V and adsorbed PVP concentration c using the unidirectional growth technique.

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Understanding the thermal properties of methane hydrate (MH)-bearing sediments is important to develop future energy resources. Thus, in this study, we measured the thermal properties of synthetic hydrate-bearing sediment samples comprising sand, water, methane, and MH using the hot-disk transient plane source technique. The melting heat of MH possibly affects the measurements; thus, the experiments were performed at supercooled conditions during MH formation in the sediment pores. The results show that thermal conductivity and diffusivity of the samples slightly increased as hydrate saturation increased from 0 to 0.3. We also performed thermal conductivity calculations using simple thermophysical models. The distribution model (geometric mean model) shows a relatively good agreement with the experimental data; however, it underestimates the thermal conductivity of the four-component sample. Thus, better prediction models are required to accurately determine the thermal properties of four-component systems.

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