Gas hydrates are fascinating ice-like compounds made of water cages that retain various types of guest molecules. Natural gas hydrates on Earth form below the seafloor and permafrost and contain mainly methane (CH4). Methane from hydrate deposits could be considered as an energy resource. One possible production scenario of CH4 from hydrates is the injection of carbon dioxide (CO2) or carbon dioxide-nitrogen(CO2-N2) mixed gas into the reservoir. Depending on the thermodynamic constraints, the composition of the gas hydrate guest molecules changes: the energy source CH4 is released and the greenhouse gas CO2 is trapped. The aim of the present work is to study the mixed gas hydrates that form in gas hydrate reservoirs after injection of CO2 or CO2-N2 gas mixtures, using laboratory experiments and modeling.