Formation Behaviors of CO2 Hydrate in Kaoline and Bentonite Clays with Partially Water Saturated

Abstract

CO2 hydrates can be used for long term storage of CO2 in the deep ocean. Clay minerals are the most important components of the marine sediments. In this study, the formation behaviors of carbon dioxide hydrate in kaoline clay and bentonite clay with partially water saturated were studied in a closed system. The mass ratio of water to Kaoline and Bentonite clays is 20%. The experiments were carried out at the temperature of 279.15 K and the initial formation pressure range of 4.8-3.4 MPa. The liquefaction of the carbon dioxide was observed in the cooling process by setting the temperature of the water bath to the valued experimental temperature. The temperature in the crystallizer begins to rise quickly when the hydrate starts to form and then decreases gradually after reaching the highest value. For the experiments in kaoline clay, the temperature decreases gradually along with the equilibrium hydrate formation temperature, and the hydrate formation rate is controlled by the heat transfer process. The final conversion of the water to hydrate increases with the increase of the initial formation pressure and restrained by the equilibrium hydrate formation pressure. For the experiments in bentonite clay, the temperature during the hydrate formation is much higher than the equilibrium temperature for CO2 hydrate formation. The final pressure is much higher than the equilibrium pressure of CO2 hydrate, and increases with the increase of the initial formation pressure, indicating that the equilibrium pressure CO2 hydrate in bentonite clay is higher than the bulk CO2 hydrate.