Methane hydrate is considered as a promising energy resource for the near future. To predict the gas productivity from the methane hydrate in the subsea sand-sediment, it is important to know absolute permeability accurately of the sediment bearing methane hydrate. Hence, the hydrate morphological distribution: namely, what is the shape and morphology of hydrate, in the sediment should be elucidated, because the permeability is strongly affected by the hydrate distribution. In this study, to know where hydrate is formed in the pore of porous media, we proposed a numerical model for estimating the microscopic distribution of methane hydrate in sand sediment, using the classical nucleation theory and the phase-field model. The former theory gave the probabilities of hydrate nucleation positions in the gas-water-sand three-phases and the latter method provided the mobility of the front of the hydrate formation. A necessary hydrate formation rate constant was determined by history-matching with an experiment in the literature. Using the obtained rate constant, we numerically simulated hydrate formations within the microscopic computational domains.

甲烷水合物被认为是在不久的将来很有前途的能源。为了从海底沙沉积物中的甲烷水合物预测气体生产率，重要的是准确知道带有甲烷水合物的沉积物的绝对渗透率。因此，应阐明沉积物中的水合物形态分布，即水合物的形状和形态是什么，因为渗透率受水合物分布的强烈影响。在这项研究中，要了解多孔介质孔隙中水合物的形成位置，我们使用经典的成核理论和相场模型提出了一个数值模型，用于估算砂沉积物中甲烷水合物的微观分布。前者提供了水-气-砂三相中水合物成核位置的可能性，后一种方法提供了水合物形成前沿的迁移率。通过历史匹配和文献中的实验来确定必要的水合物形成速率常数。使用获得的速率常数，我们在微观计算域内对水合物的形成进行了数值模拟。