SUBSURFACE CARBON DIOXIDE STORAGE THROUGH CLATHRATE HYDRATE FORMATION

摘要

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 CO_2 storage (viz. geologic disposal into coal seams, depleted oil/gas reservoirs, salt caverns, and deep oceans) have already been reported in the literature. Subsurface CO_2 storage through clathrate hydrate formation is a novel option for the reduction of atmospheric carbon content and permanent underground CO_2 disposal over geological periods. Depths of CO_2 injection, respective pressure-temperature conditions, water salinity etc. are all important factors for successful CO_2 sequestration. Furthermore if CO_2 is injected/stored in methane hydrate reservoirs it could be possible to produce low-carbon methane energy, thereby offsetting the cost of CO_2 transportation and disposal. In this communication, we present the results of experiments carried out to understand the mechanisms of CH_4 displacement in hydrate structure by injected CO_2 and the formation of simple CO_2 or mixed CH_4-CO_2 hydrates, thereby simulating the conditions of CO_2 injection into CH_4 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 CO_2 sequestration in CH_4 hydrates in synthetic porous media.