Experimental Studies on Gas Hydrate-Based CO2 Storage: State-of-the-Art and Future Research Directions

Hydrate-based CO2 storage is considered a potentially effective way of reducing greenhouse gas emissions and slowing down global warming. Herein, the locations in the ocean and permafrost that meet the requirements for hydrate-based CO2 storage are summarized. Furthermore, research progress and shortcomings of hydrate-based CO2 storage are analyzed. The two main methods for hydrate-based CO2 storage are direct CO2 hydrate storage and CO2-CH4 hydrate replacement. Direct CO2 hydrate storage on the seabed and in the subsea (or permafrost) is proposed, and CO2 formation experiments on different scales are conducted. Various porous media are used to simulate the natural sediment and investigate the hydrate formation equilibrium and kinetics. CO2-CH4 replacement is preferred because it combines the benefits of CO2 storage and CH4 production. The hydrate equilibrium of different CO2-CH4 mixture hydrates is measured using different methods. Nuclear magnetic resonance and Raman spectroscopy are commonly used to study the hydrate structure characteristics and mass transfer properties. Macrokinetics are usually conducted in a high-pressure vessel to analyze the effects of the experimental conditions on the replacement results. Nevertheless, the replacement rate and hydrate properties should be investigated further.