Thermal properties of highly saturated methane hydrate-bearing sediments recovered from the Krishna–Godavari Basin

Abstract

Abstract We measured the thermal constants (including conductivity, specific heat, and thermal diffusivity) of methane hydrate (MH)–bearing sediment samples recovered in 2015 from the Krishna–Godavari Basin, in India. These samples were recovered through the National Gas Hydrate Program Expedition 02 (NGHP-02). The measurements were performed using the single-sided Transient Plane Source (TPS) method. To investigate the influence of the sediment composition on the thermal properties of MH-bearing sediments, the thermal constants of MH-bearing sediments were measured at 5\u202f°C and 10\u202fMPa over a porosity (ϕ) range of 41%\u202f≤\u202fϕ\u202f≤\u202f51% and MH saturation (Sh) range of 17%\u202f≤\u202fSh\u202f≤\u202f74%. In addition, density and mineral compositional measurements of the dry sediment grain samples were conducted. The measured thermal conductivity slightly decreases with increasing ϕ and is independent of Sh. The measured specific heat increased with increasing ϕ, whereas it decreased with increasing Sh. The measured thermal diffusivity decreased with increasing ϕ, whereas it increased with increasing Sh. Various models were used to estimate the thermal constants to examine the applicability of these models to natural MH-bearing sediments. The distribution model (using a geometric mean model) is valid from the low to high MH saturations; however, the thermal properties of clay-rich layers are not likely reproducible by the distribution model from the mineral compositions. This indicates that the low value of the observed thermal conductivity in the clay-rich samples is likely a product of the sediment s small grain size.