Guest-exchange Behaviors of Different Hydrocarbons with CO2 + N2 Occurring in SII Mixed Hydrates
Abstract
The replacement of SII CH4-C2H6-C3H8 hydrates in sandy sediments by CO2/N2 is studied to investigate the gas recovery from SII gas hydrate reservoirs. It was found that CH4 was the easiest one to be replaced in all experiments, and CO2/N2 played different roles during replacement in different CO2 concentrations. Particularly, the addition of N2 in replacement gas can cause the decrease in the replacement efficiency, which was related with the difference in swapping patterns. The increase of the N2 concentration may strengthen the structural stability of SII hydrates and lead to reducing the portion of SII hydrates transformed into SI hydrates.
Keywords: gas hydrate, CO2+N2, structure II, replacement efficiency
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