Experimental study on the formation characteristics of CO2 hydrate in porous media below the freezing point: Influence of particle size and temperature on the formation process and storage capacity

Abstract

AbstractCO2 storage in form of hydrate in stratigraphic sediment has been considered to be one of the effective strategies against global warming and mitigating CO2 emission, which has attracted extensive research interest in the field of greenhouse gas (GHG) reduction and natural gas hydrate exploitation in permafrost regions. How the formation characteristics of CO2 hydrate influences the storage process is a fundamental issue related to the hydrate‐based technology of CO2 sequestration and storage in the permafrost regions. In this study, the formation experiments of CO2 hydrate were carried out in porous media below freezing point under the condition of different particle sizes and temperatures. The influence of different factors on the formation rate, conversion rate, and gas storage capacity of CO2 hydrate were studied through experiments. It was indicated that temperature and ice particle size had a significant effect on the formation characteristics of CO2 hydrate in porous media below the freezing point. However, it did not mean that the greater the degree of supercooling was the better the hydrate formation would be. The formation rate and conversion rate of hydrate were relatively higher when the temperature approached to the freezing point. In contrast, the gas storage capacity of CO2 hydrate was higher than that above the freezing point. The average formation rate, conversion rate, and gas storage capacity of CO2 hydrate were obtained under the temperature of 270.15 K, which was 3.68 × 10−4 mol h−1, 40.47%, and 75.09 L/L, respectively. When the ice particle size was 700 µm under the same particle size of quartz sand, the conversion rate and gas storage capacity of CO2 hydrate was the maximum, reached to 49.69% and 92.19 L/L, respectively. These results provide greater insights into the hydrate‐based technology of CO2 sequestration and storage in sediments.