Investigation of the formation behaviors of CO₂ hydrate in porous media below the freezing point

Abstract

The formation process of gas hydrate is a stochastic phenomenon considered to be significant for its application in the areas such as hydrate-based technology and natural gas hydrate exploitation. The formation behaviors of CO 2 hydrate were studied in porous media below the freezing point. In addition, the formation experiments were conducted in the high-pressure vessel under different temperature and pressure conditions. The formation process of CO 2 hydrate showed different formation behaviors in the porous media under different experimental conditions. The results showed that the formation rate was higher in earlier stage and the largest formation rate attained 7.18 Â 10 À4 mol h À1 . The influence of initial pressure on the formation rate was indistinctive in porous media below the freezing point. Particle size of the porous media played an important role in affecting the formation characteristic of CO 2 hydrate below the freezing point. The results indicated that, the smaller the particle size of porous media was, the larger the formation rate and the conversion rate of CO 2 hydrate. The maximum conversion rate was attained 90.61%. The results also indicated that CO 2 hydrate had a good gas storage capacity in porous media below the freezing point. The gas storage capacity was close to 160 L/L in frozen quartz sand with the particle size of 250 μm in the experiments. The relative results will provide some insight for sequestration and storage process of CO 2 gas in the form of hydrates into sediments.