MODELING AND SIMULATION OF CARBON DIOXIDE REPLACEMENT IN METHANE HYDRATE IN PURPOSE OF METHANE RECOVERY

Large amount of natural gas exists in the form of gas hydrate in subsea sediment and permafrost regions. There are some traditional methods for the dissociation of hydrate and recovery of methane, include depressurization, thermal stimulation and chemicals injection. An alternative approach proposed in the past decade is replacement of carbon dioxide in methane hydrate. It has advantages of recovering methane gas as an important energy resource and mitigating greenhouse gas of carbon dioxide in the atmosphere. In this article, kinetic model is proposed for replacement process and effects of operating parameters suchas system total pressure, diffusion coefficient of CH4 in the hydrate layer and initial mole fraction of CO2in gas phase on the replacement efficiency are simulated. It concluded that replacement rate and the mole fraction of CH4 in gas phase increases with increasing initial CO2 mole fraction and diffusion coefficient while decreasing with system total pressure. We have also proposed a Distributed model for predicting thediffusion of gases CO2 in the CH4 hydrate layer and solved with COMSOL Multiphysics software. Theresults showed that gases CO2 can diffuses into CH4 hydrate layer only about 53% of reactor volume and about 87% of reactor volume is affected by temperature variation along the reactor due to replacement process.

Keywords:

Hydrate , Methane , Carbon dioxide , Replacement , Kinetic