Abstract The formation sands of natural gas hydrate (NGH) reservoirs in the South China Sea are fine silty sands with a high content of clay, and it is difficult to be controlled effectively. We carried out a series of experiments to investigate the microcosmic retaining and plugging behavior of screen media with highly argillaceous fine sand samples, with median size of 10.13 μm. The screen sand-retention media and joint involved four types with slot width or accuracy of 20–60 μm. The screen media/joint sample was placed in the linear/radial flowing apparatus, and then the mixture of gas, water and sand were displaced flowing into the media to simulate the sand retaining process. The Microscopic imaging system was used to visually observe the dynamics of sand particle deposition and plugging inside the media as well as on its surface. The plugging permeability and the amount of the passed sand were also analyzed. According to the result, three microcosmic mechanisms of sand retaining and plugging were proposed, concerning fine sand invading and coarse sand bridge, partial sand block, and integrated sand bridge. The plugging permeability performance of screen media generally shows three stages of slow decreasing, rapid increasing and balance. At the balance stage of displacement, the plugging permeability of media sample mostly decreases more than 90%. During the whole test, the sand passing rate tends to slow down gradually, and the final retained sand ratio were more than 85%. Different configurations of sand retraining test show a little difference in plugging performance, depending on the factors of medium type, accuracy, sand characteristics, and flow conditions. Based on the effect of sand retaining and final flow ability observed in these experiments, the sand control in NGH reservoirs with highly argillaceous fine sands is practicable.

中文翻译：

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天然气水合物储层高泥质细砂筛网介质的微观截留机理与行为

摘要 南海天然气水合物（NGH）储层地层砂为细粉砂，粘土含量高，难以有效控制。我们进行了一系列实验，研究了筛网介质对高泥质细砂样品的微观截留和堵塞行为，中值粒径为 10.13 μm。筛网滞砂介质和接缝涉及四种类型，槽宽或精度为20-60μm。将筛网介质/接头试样置于线性/径向流动装置中，然后将气体、水和砂的混合物置换流入介质中以模拟挡砂过程。显微成像系统用于直观地观察砂粒沉积和堵塞介质内部及其表面的动力学。还分析了堵塞渗透率和通过的砂量。据此，提出了细砂侵入粗砂桥、局部砂块和整体砂桥三种挡砂堵堵的微观机制。筛管介质的堵漏性能一般表现为缓降、急升和平衡三个阶段。在驱替平衡阶段，介质样品的封堵渗透率大多下降90%以上。整个试验过程中，过砂率逐渐降低，最终留砂率在85%以上。不同配置的补砂试验，其堵漏性能略有不同，这取决于介质类型、精度、砂体特性和流动条件等因素。