Study on the Physical Changes of Structure I Methane Hydrate under External Forces

The ocean, continental shelf, and permafrost are abundant in CH
4
hydrates, rendering them highly promising sources of clean energy. The mechanical stability of CH
4
hydrate plays a crucial role in their extraction and storage. Being solid in nature, external forces, such as earthquakes, can induce physical damage to CH
4
hydrates. This study employs the molecular dynamics method to simulate the uniaxial-deformation behavior of structure I (sI type) CH
4
hydrate under stress. Irrespective of the application of either stretch or squeeze force, alterations in the physical parameters were observed, encompassing variations in the count of hydrate cages, order parameters, and the quantity of water molecules in both the liquid and solid phases. It was ascertained that upon complete separation of the hydrate, the stress promptly reverts to a value of about 0 GPa. During the process of squeezing, the stress remains non-zero as a result of continuous contact between the solid and liquid phases. When the hydrate is subjected to stretching, approximately 5% of water molecules undergo a phase transition from solid to liquid, while approximately 8% of CH
4
molecules lose their encapsulation and become free. Conversely, during the compression phase, the larger cages (5
¹²
6
²
) are more susceptible to deformation compared to the smaller cages (5
¹²
). Ultimately, nearly all of the larger cages and 92% of the smaller cages are crushed, leading to the liberation of approximately 97.6% of the CH
4
from the cages. This significant release of CH4 presents a potential security concern.