Subsurface CO2 storage through clathrate hydrate formation

Rising atmospheric emissions as a result of fossil fuel consumption is a major concern for the developed and developing countries, considering the role it plays in the greenhouse effect and hence global climate change. Various schemes for underground CO2 storage (viz. geologic disposal into coal seams, depleted oil/gas reservoirs, salt caverns, and deep oceans) have already been reported in the literature. Subsurface CO2 storage through clathrate hydrate formation is a novel option for the reduction of atmospheric carbon content and permanent underground CO2 disposal over geological periods. Depths of CO2 injection, respective pressure-temperature conditions, water salinity etc. are all important factors for successful CO2 sequestration. Furthermore if CO2 is injected/stored in methane hydrate reservoirs it could be possible to produce low-carbon methane energy, thereby offsetting the cost of CO2 transportation and disposal. In this communication, we present the results of experiments carried out to understand the mechanisms of CH4 displacement in hydrate structure by injected CO2 and the formation of simple CO2 or mixed CH4-CO2 hydrates, thereby simulating the conditions of CO2 injection into CH4 hydrate reservoirs. We used two sets of experimental rigs specifically designed for studying gas hydrates in porous media. They are the Medium Pressure Glass Micromodel (80 bar) for visual observation of gas hydrate formation / dissociation and distribution in porous media, and the Ultrasonic Rig (400 bar) for studying CO2 sequestration in CH4 hydrates in synthetic porous media.