CAJ | 학술논문

We modeled and studied the permeability of methane hydrate bearing formations as a function of methane hydrate concentration by artificially varying the T2 distribution as well as using a tube-sphere model. We varied the proportion of irreducible and movable water as well as the total porosity associated with the T2 distribution and found the normalized permeability as a function of methane hydrate concentration is dependent of these variations. Using a tube-sphere model, we increased the methane hydrate concentration by randomly placing methane hydrate crystals in the pore spaces and computed the permeability using either the Schlumberger T2 relaxation time formula or a direct calculation based on Darcy's law assuming Poiseuille flow. Earlier experimental measurements reported in the literature show there is a methane hydrate concentration range where the permeability remains relatively constant. We found that when the Schlumberger T2 relaxation time formulais used the simulation results show a curve of normalized permeability versus methane hydrate concentration quite close to that predicted by the Masuda model with N = 15. When the permeability was directly calculated based on Darcy's law, the simulation results show a much higher normalized permeability and only show a trend consistent with the experimental results, i.e., with a permeability plateau, when the methane hydrate crystals are preferentially placed in the tubes, and the higher the preferential probability, the larger the range where the permeability has a plateau.