Molecular Dynamics Study for the Enhancement of Carbon Dioxide Exchange in Methane Hydrates.

Decline in the fossil energy reserves and increase in the pollution of the environment due to the greenhouse gases like CO₂ could be solved simultaneously if CO₂ is sequestered in methane hydrate reservoirs to release the trapped methane. This process may be optimized to enhance methane gas recovery. This approach is thermodynamically feasible due to a higher stability of carbon dioxide hydrates as compared to that of methane hydrates. However, exchange of methane with CO₂ is limited by replacement kinetics and it has been verified experimentally. This study looks into the replacement mechanism at molecular level. One of the objectives is to identify ways by which the replacement kinetics could be enhanced. Further, it also checks the possibility to extract more methane out of the same hydrate field if a suitable additive is used along with CO₂. Properties like host lattice relaxation, guest-guest interactions, defects caused in the structure when a tertiary molecule and a water soluble additive is added to enhance the process, is studied. It is observed that this water soluble additive potentially introduces defects in the hydrate crystal and thus enhances the methane recovery when exposed with another hydrate former like CO₂.