Simultaneous measurement of water permeability and methane hydrate pore habit using a two-dimensional glass micromodel

In this study, we developed an in situ chamber to measure water permeability as a function of the methane hydrate (MH) habit in pore space using a two-dimensional glass micromodel by adding a methane-dissolved water source unit to prevent MH dissociation. This unit enabled us to adjust the amount of methane dissolved in the water by controlling the pressure and temperature. We simultaneously observed MH crystallization behavior and measured the water permeability of the porous media. The growth rate of MH and the pore habit formation changed with subcooling, Delta T. As Delta T increased, the shape of the pattern transformed from a hexagonal plate to a dendrite and hexagonal plate, and finally, to a dendrite. The glass pillar played a role in inhibiting the growth of dendritic patterns. The plugging process of the porous media following MH formation was also observed. We compared our results with various water permeability models of MH sediments and found that the nonempirical relative permeability (NRP) models showed relatively good agreement. This was likely because the NRP models enhanced the effect of the gas phase. However, a gap remains between the NRP model predictions and our experimental results. On the other hand, there was no possibility of agreement other than the NRP models because the gas phase was not included in the equation.