Abstract The properties of gas hydrate bearing sediments (GHBS) depend on their changing morphology and wettability characteristics, which are in turn important for efficiency and safety issues during production. We present the results of xenon hydrate formation experiments using quartz sand packs at different salinities. Direct 3D visualization of hydrate distribution in the pore space was obtained with the help of high-resolution micro-computed tomography (CT). Four phases, xenon hydrate, xenon gas, brine and quartz sands were segmented and labelled in the raw micro-CT scanned images. A 3D reconstruction reveals typical pore-scale patterns of hydrate occurrence (pore-filling, grain-coating) and shows that hydrate preferentially aggregates at the gas-water interface, reflecting greater local access to xenon gas molecules. The hydrate cluster shape factor ranges from 2 to 10, indicating that xenon hydrate forms with a complex and irregular microstructure, consistent with random growth nature of hydrate. The hydrate saturation is found to decrease with salinity under excess-gas condition, which we interpret in terms of the hydrate formation kinetics to indicate that gas hydrate prefers to grow into the gas phase at the gas-water interface. A total of 270 local contact angles of water at the gas and hydrate interfaces in pores were measured with a micro-CT image analysis method to obtain information on the wettability variation of hydrate surfaces. The average was calculated to be 47.6°, indicating that xenon hydrate surface is hydrophilic. Our analysis of the xenon hydrate morphology provides a new method for revealing hydrate growth behavior at pore-scale. The wettability characterization offers key parameters for accurate numerical simulation of multiphase flow prediction and seepage behavior in GHBS.

中文翻译：

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砂基质中氙水合物的孔隙尺度形态和润湿性特征——微CT实验室可视化

摘要 含天然气水合物沉积物（GHBS）的性质取决于其不断变化的形态和润湿性特征，而这反过来又对生产过程中的效率和安全问题很重要。我们展示了在不同盐度下使用石英砂堆形成氙水合物的实验结果。在高分辨率显微计算机断层扫描 (CT) 的帮助下，获得了孔隙空间中水合物分布的直接 3D 可视化。在原始显微 CT 扫描图像中分割并标记了四相，氙水合物、氙气、盐水和石英砂。3D 重建揭示了水合物生成的典型孔隙尺度模式（孔隙填充、颗粒涂层），并表明水合物优先聚集在气水界面，这反映了氙气分子的局部通路。水合物簇形状因子的范围为 2 到 10，表明氙水合物形成具有复杂且不规则的微观结构，与水合物的随机生长性质一致。发现在过量气体条件下水合物饱和度随盐度降低，我们根据水合物形成动力学解释这表明气体水合物更喜欢在气水界面处生长成气相。使用显微CT图像分析方法测量了孔隙中气体和水合物界面处水的总共270个局部接触角，以获得有关水合物表面润湿性变化的信息。经计算得出的平均值为 47.6°，表明氙水合物表面是亲水的。我们对氙水合物形态的分析提供了一种在孔隙尺度上揭示水合物生长行为的新方法。