Guest-exchange Behaviors of Different Hydrocarbons with CO2 + N2 Occurring in SII Mixed Hydrates

Abstract

The replacement of SII CH 4 -C 2 H 6 -C 3 H 8 hydrates in sandy sediments by CO 2 /N 2 is studied to investigate the gas recovery from SII gas hydrate reservoirs. It was found that CH 4 was the easiest one to be replaced in all experiments, and CO 2 /N 2 played different roles during replacement in different CO 2 concentrations. Particularly, the addition of N 2 in replacement gas can cause the decrease in the replacement efficiency, which was related with the difference in swapping patterns. The increase of the N 2 concentration may strengthen the structural stability of SII hydrates and lead to reducing the portion of SII hydrates transformed into SI hydrates.