Reservoir Modeling of Production of CH4 from Natural Gas Hydrates by Injection of a CO2+N2 Gas Mixture

Natural gas hydrates are non-stoichiometric crystalline inclusion compounds are likely to contain more carbon than in all other fossil fuel reserves combined. Different techniques that are currently being proposed for production of CH4 from the gas hydrates include depressurization, thermal stimulation and injection of inhibitors (Sloan and Koh, 2007). These methods involve dissociation of gas hydrate and the release of a significant amount of water that may cause geomechanical stresses on the reservoir that could lead to subsidence. A newly proposed method is to replace CH4 in the hydrate by the injection of pure CO2 or CO2+N2 mixtures, which serves dual purpose of long-term storage of a greenhouse gas (CO2) and the production of natural gas, while maintaining the hydrate structure in situ (Ohgaki et al., 1996), thus making the operation carbon neutral.