Mechanical properties of remolded hydrate-bearing clayey-silty sediments

The vast majority of global gas hydrate resources exist in clay and silty fine-grained reservoirs, so fully grasping the mechanical properties of fine-grained hydrate is the key to realize the commercialization of hydrate resources. To date, the research on mechanical properties of hydrates has focused on sandy sediments, while research on the fine-grained hydrate has been relatively less common. In this paper, clay collected from the South China Sea and quartz sand were used to remold hydrate-bearing clayey-silty sediments (HBCSS). A series of triaxial shear tests were then carried out to explore the effects of hydrate saturation, effective confining pressure and clay content on the mechanical properties of HBCSS. This study not only reveals the influence of different factors on the mechanical properties of HBCSS, but also explains the action mechanism of clay. The results show that a higher hydrate saturation could cause strain softening due to spalling and crushing of hydrate particles, and this strain softening effect will also be affected by confining pressure. The failure strength of HBCSS increases with the increase of hydrate saturation and effective confining pressure, but decreases with the increase of clay content. The action mechanism of clay is the effect of lubrication, which can change the particle relationship from crushing to rotating or sliding. This research could be valuable for the safe and efficient exploitation of claybearing fine-grained hydrate.

Automated summary

The majority of global gas hydrate resources are located in clay and silty fine-grained reservoirs. Understanding the mechanical properties of fine-grained hydrate is crucial for its commercialization. However, research on the mechanical properties of fine-grained hydrate has been relatively limited. In this study, experiments were conducted using clay from the South China Sea and quartz sand to investigate the effects of hydrate saturation, effective confining pressure, and clay content on the mechanical properties of hydrate-bearing clayey-silty sediments. The results show that higher hydrate saturation can cause strain softening, and the clay acts as a lubricant, changing the particle relationship from crushing to rotating or sliding.