The self-preservation effect is crucial for hydrate storage, however, may also hinder the decomposition and even results in severe plug of production well for hydrates exploitation below freezing point. In this study, a high pressure micro-differential scanning calorimeter (HP μ-DSC) was used to study the effect of sediment particle size and type on the self-preservation of CH4 hydrate with low saturation. It was found that there is still a strong self-preservation effect, and the stability of CH4 hydrate degrades with the reduced sediment particle size as a whole. The CH4 hydrates, in different sediments, have significant differences of self-preservation phenomena. CCD camera and in-situ raman spectroscopy was used to further investigate the influence mechanism. The experimental results indicate that the ice and bentonite synergistically enhanced the self-preservation effect of CH4 hydrate, which should be paid great attention to the gas production process of hydrate below freezing point in the future. This is the first investigation on the sediment influence on self-preservation effect of methane hydrate. Our findings are of significance for both risk prevention of hydrate exploitation and a better understanding of self-preservation effect.
Keywords CH4 hydrate, self-preservation effect, sediment type, sediment particle size, dissociation