This work presents details on the experimental procedure to measure the composition of the hydrate that crystallizes from a hydrocarbon gas mixture. We show that the results are time dependent and tend to thermodynamic equilibrium as time tends to infinity. An immediate consequence concerns two major domains of applications, CO₂ capture from power plants, as well as flow assurance in the oil and gas industry. In fact, in both the cases, the crystallization is under non equilibrium conditions, and we conclude here that it necessarily leads to the formation of hydrates with a composition which is not predicted by classical modeling.Conclusion:Hydrate equilibria are given (T, P, gas and hydrate compositions) following two procedures.The two procedures used (high and low crystallization rates) highlight the kinetic effect on hydrate formation.In the end this work, there is a questioning about the validity of measurements: Are they thermodynamic of kinetic measurements? This is why the present data were analyzed using a thermodynamic model in an in-house software to discuss the possibility to crystallize gas hydrate at thermodynamic equilibrium at a low and high crystallization rate [Herri et al., 2014]