The effect of grainsize of sediments in the CO2/CH4 replacement process within a hydrate lattice: An experimental report

The effects of natural parameters and their related properties, on the formation and dissociation of gas hydrates, have been widely investigated and satisfying information can be found elsewhere in literature. Conversely, there is a substantial lack of similar studies related to CO2/CH4 replacement processes. This research aims to contribute in this sense and shows replacement tests in presence of two pure silica porous media, whose only difference stays in the size of grains. The results confirmed what asserted in literature for the simple formation of hydrates and provided new insights about the replacement process. It was found that the lower size of grains favoured the formation of hydrates and their stability. Precisely for this reason, the fine sediment hindered the replacement, because the higher stability of methane hydrates reduced the capability of CO2 molecules to penetrate within the sediment and take the place of methane molecules. This study proved once again that, natural elements capable to act as promoter for the formation of hydrates, often have an inhibiting effect on the replacement processes.