Hydrate formation is an inhomogeneous process, which results in permeability anisotropy, i.e., permeability differs in different directions. Permeability anisotropy of hydrate-bearing sands is analyzed based on CT (computed tomography) scanning and pore network modeling in this study. A digital sample is divided into eight different parts based on hydrate distribution. Eight equivalent micropore structures are extracted by the maximum ball method. The absolute and relative permeabilities of each part in three different directions (x, y, and z) are calculated by a permeability simulator. Before hydrate formation, the sand pack permeability in the different directions is nearly the same. After hydrate formation, the sample pore structures become more complex. Both the absolute and relative permeabilities vary in the different directions. When hydrate saturation exceeds a threshold, the degree of permeability anisotropy is weakened. Hydrate formation induces a more significant relative gas permeability anisotropy compared to relative water permeability anisotropy. The degree of relative water permeability anisotropy increases at high water saturations.

中文翻译：

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非均质水合物形成对多孔介质渗透率各向异性的影响

水合物形成是一个非均质过程，导致渗透率各向异性，即不同方向渗透率不同。本研究基于CT（计算机断层扫描）扫描和孔隙网络建模分析了含水合物砂岩的渗透率各向异性。数字样本根据水合物分布分为八个不同的部分。通过最大球法提取了八个等效微孔结构。每个部分在三个不同方向（x、y 和 z）的绝对和相对渗透率由渗透率模拟器计算。在水合物形成之前，不同方向的砂包渗透率几乎相同。水合物形成后，样品孔隙结构变得更加复杂。绝对渗透率和相对渗透率在不同方向上都不同。当水合物饱和度超过阈值时，渗透率各向异性程度减弱。与相对水渗透率各向异性相比，水合物形成引起更显着的相对气体渗透率各向异性。相对水渗透率各向异性的程度在高水饱和度时增加。