Particle size effect on the saturation of methane hydrate in sediments – Constrained from experimental results

Except for those occurring at seafloor, most of natural gas hydrate form in sediments and are subject to the influence of sediment. Among these factors, the particle size effect on hydrate saturation level in sediment have been studied with a series of silica sands with various sizes, and the results obtained clearly indicate that particle size does play an important role in affecting the saturation level of hydrate in sediments. The proton relaxation times of water confined in the same series of silica sands, which were determined with NMR measurement, show logarithmic relationship with particle size. By comprehensive consideration of the results of hydrate saturation and water proton relaxation times, the particle size effect observed is tentatively explained by the water availability for hydrate formation in sediments. ► The particle-size effect on the saturation of gas hydrate in sediments has been confirmed by experimental results with a series of silica sands with various sizes. ► The proton relaxation times of water in silica sands, which were determined with NMR measurement, show logarithmic relationship with particle size. ► The comprehensive analysis of the hydrate stability and saturation data in silica sands revealed that gas hydrate was only formed in the bulk water in sediment pore. ► The mechanism of particle-size effect on hydrate saturation can be tentatively explained by the water availability in sediments.