Sand production greatly influences reservoir stability and safety during gas hydrate exploitation in hydrate-bearing sediments (HBS). Gravel packing is an effective method for sand control. Median grain size ratio (D₅₀/d₅₀) values and sand migration of gravel pack are important factors in sand control during gas hydrate exploitation. This paper focuses on sand migration in samples with an optimal (D₅₀/d₅₀) value during the hydrate dissociation process. Four samples with different D₅₀/d₅₀ values were tested to obtain the optimal D₅₀/d₅₀ for gas hydrate exploitation. Then, a sand migration experiment was conducted on the sand sample with the optimal D₅₀/d₅₀ with X-ray computed tomography (CT) to obtain the sand migration during the hydrate dissociation process. The results showed that 6.5 was the optimal D₅₀/d₅₀ value for the selection of the gravel median grain size. The occurrence of sand-bridge structures in the pore space of the sample (D₅₀/d₅₀ = 6.5) was a significant phenomenon during hydrate dissociation and were beneficial to both gas production and sand control. Free sand migrated in the pore space of the mixed sample (D₅₀/d₅₀ = 6.5) and formed sand-bridge structures due to hydrate dissociation. The formation and destruction of trapped gas structures were mainly influenced by sand-bridge structures caused by sand migration. The results in this paper could provide useful insight into sand production behaviors induced by sustainable gas production in HBS.

在含水合物沉积物（HBS）中开采天然气水合物期间，出砂会极大地影响储层的稳定性和安全性。碎石填充是防砂的有效方法。中值粒径比（D ₅₀ / d ₅₀）值和砾石充填的砂迁移是控制天然气水合物开采过程中防砂的重要因素。本文关注水合物分解过程中具有最佳（D ₅₀ / d ₅₀）值的样品中的砂迁移。测试了四个具有不同D ₅₀ / d ₅₀值的样品，以获得最佳D ₅₀ / d ₅₀用于天然气水合物的开采。然后，用X射线计算机断层扫描（CT）对具有最佳D ₅₀ / d ₅₀的砂样品进行了砂迁移实验，以获得在水合物分解过程中的砂迁移。结果表明，选择砾石中值粒径的最佳D ₅₀ / d ₅₀值为6.5 。样品孔隙空间中砂桥结构的出现（D ₅₀ / d ₅₀  = 6.5）是水合物分解过程中的重要现象，有利于产气和防砂。游离砂在混合样品的孔隙中迁移（D ₅₀ / d ₅₀ = 6.5）并由于水合物分解而形成砂桥结构。夹杂气结构的形成和破坏主要受砂运移引起的砂桥结构的影响。本文的结果可以为HBS可持续天然气生产引起的出砂行为提供有用的见解。