Dissociation characteristic of methane hydrate in clayey silt below the ice point

As an important clean energy resource, natural gas hydrates (NGHs) have attracted considerable research interest. Gas recovery efficiency is an important factor affecting the commercial development of NGHs. Owing to the endothermic reaction of NGH dissociation, the temperature of the local hydrate reservoir may be greatly reduced. The dissociation characteristics of NGHs at low temperature may significantly affect the gas production efficiency. More than 90% of the world's NGHs exist in low-permeability fine-grained sediments, and the dissociation behaviors of NGHs in these media below the ice point are not fully understood. In this study, the dissociation characteristics of the hydrate in clayey-silt were tested at negative temperatures. Clayey-silt samples were prepared according to the characteristics of cores recovered in the South China Sea. After methane hydrate formed in the samples, its dissociation rate was tested under different negative temperatures. The results show that the methane hydrate had a low dissociation rate between 243 K and 253 K in the clayey-silt samples. More than 90% of the methane hydrate was preserved within 24 h. The stability of methane hydrate is related not only to dissociation pressure but also to a metastable state. Methane hydrate in clayey-silt has high stability in metastable region. The stability of gas hydrate under negative temperatures has great potential application value in the field of gas storage.