Characterization of permeability and thermal conductivity of methane hydrate sediments using microfocous X-ray computed tomography technique

Abstract

Permeability and thermal conductivity of natural gas hydrate sediments were characterized using a microfocus X-ray computed tomography (CT) technique. The free-gas spaces, sand particles, and hydrates or ices were identified from the obtained three-dimensional X-ray CT images, from which continuous pore networks were identified. The absolute permeability of the sediment correlated well increased with the ratio of parallel to vertical directions of continuous pore numbers. This fact indicates that the pore network in sediment can be useful for assessment of permeability. In order to characterize the thermal conductivity of methane hydrate sediments, a homogenization method was applied to microfocus X-ray CT images. The thermal conductivity calculated from three dimensional X-ray CT images was good agreement to those measured by the hot disk method, when the thermal conductivity of sand particles is 0.5 W/mK. These results demonstrated that the microfocus X-ray CT imaging can be effective for studying material flow and thermo-mechanical properties of natural gas hydrate sediments.