PRODUCTION OF sI AND sII HYDRATES WITH BINARY MIXTURES CONTAINING CH4 AND LOWER CONCENTRATIONS OF C2H6/C3H8: POSSIBLE CONSEQENCES ON REPLACEMENT IN MARINE NATURAL DEPOSITS

The most attractive option to recover methane trapped within natural gas hydrate reservoirs, consists of the so-called �replacement process�, mainly based on the contemporary injection of carbon dioxide during the mining process. If appropriately carried out, this process allows to improve the amount of methane recovered, preserve the crystalline hydrate cages and permanently store enough carbon dioxide to make this source definitively carbon neutral. For that reason, this process is widely studied worldwide. However, most of lab-scale experiments do not consider the presence of further small-chain hydrocarbons within the natural gas mixtures. These species may be crucial in determining key properties of the system, as type of crystalline structure, overall stability, phase boundary equilibrium conditions and others. Therefore, experimentally defining how methane behaves, in terms of hydrates formation, when mixed with ethane and/or propane, is crucial to correctly calculate the CO2/CH4 replacement efficiency.