Experimental study on the stability of CO2 hydrate in submarine sediments environment

Hydrate-based CO 2 storage represents a compelling strategy for CO 2 oceanic storage. The long-term stability of CO 2 hydrates is the pivotal indicator for assessing the technical viability of this strategy. Investigation on CO 2 hydrate stability can not only quantify the risk of CO 2 leakage to the environment, but also provide the mechanistic basis for optimizing long-term, secure storage. The hydrate dissolution rate serves as the quantitative proxy for hydrate stability. Accurate quantification of CO 2 hydrates dissolution rates in marine settings is therefore imperative. This study presents a comprehensive, 200-hour experimental program to quantify the dissolution rate of CO 2 hydrate under submarine sediments environment. The porosity and true density of the reconstructed sediment used were 45% and 2.8 g/cm 3 , respectively. Factors such as temperature, pressure, and sediment cap thickness were investigated to determine the dissolution rate of CO 2 hydrates under different conditions. The dissolution rate of CO 2 hydrates increases modestly with rising temperature and pressure, yet declines precipitously as sediment cap thickens. Across the investigated parameter space, the dissolution rate spans 4.87–134.73 cm/year. In diffusion-controlled hydrate dissolution, the sediment cap dramatically suppresses the CO 2 molecular diffusion flux by simultaneously lowering porosity and increasing tortuosity. Over long-term evolution, once the local temperature and pressure conditions are established, the sediment cap thickness emerges as the predominant factor controlling the hydrate dissolution rate. These findings provide a mechanistic basis for assessing the long-term stability of CO 2 hydrates during storage and offer critical guidance for the design of enduring CO 2 hydrate storage strategies.