An Experimental Investigation on the Kinetics of Integrated Methane Recovery and CO ₂ Sequestration by Injection of Flue Gas into Permafrost Methane Hydrate Reservoirs

Abstract

Large hydrate reservoirs in the Arctic regions could provide great potentials for recovery of methane and geological storage of CO ₂. In this study, injection of flue gas into permafrost gas hydrates reservoirs has been studied in order to evaluate its use in energy recovery and CO ₂ sequestration based on the premise that it could significantly lower costs relative to other technologies available today. We have carried out a series of real-time scale experiments under realistic conditions at temperatures between 261.2 and 284.2 K and at optimum pressures defined in our previous work, in order to characterize the kinetics of the process and evaluate efficiency. Results show that the kinetics of methane release from methane hydrate and CO ₂ extracted from flue gas strongly depend on hydrate reservoir temperatures. The experiment at 261.2 K yielded a capture of 81.9% CO ₂ present in the injected flue gas, and an increase in the CH ₄ concentration in the gas phase up to 60.7 mol%, 93.3 mol%, and 98.2 mol% at optimum pressures, after depressurizing the system to dissociate CH ₄ hydrate and after depressurizing the system to CO ₂ hydrate dissociation point, respectively. This is significantly better than the maximum efficiency reported in the literature for both CO ₂ sequestration and methane recovery using flue gas injection, demonstrating the economic feasibility of direct injection flue gas into hydrate reservoirs in permafrost for methane recovery and geological capture and storage of CO ₂. Finally, the thermal stability of stored CO ₂ was investigated by heating the system and it is concluded that presence of N ₂ in the injection gas provides another safety factor for the stored CO ₂ in case of temperature change.