The current study utilizes Grand Canonical Monte Carlo simulations in order to calculate the amount of methane gas that can be stored inside hydrate structures sII and sH. The temperature and pressure conditions examined include those of interest to the industrial methane transportation, and the storage of methane in industrial settings or naturally-occurring hydrate deposits. To this purpose, the amount of methane stored in the different type of cages that form the hydrate structures is presented as Langmuir-type "absorption isotherms", which are functions of pressure, temperature and hydrate structure. The obtained expressions are subsequently used in order to identify conditions (i.e., pressure temperature, hydrate promoter molecular weight, and cage fraction occupied by the hydrate promoter) where the considered hydrate structures can have storage capacities that are higher than the storage capacity of the more common sI methane hydrate. The results are also discussed in the context of storage capacities of natural hydrates that are under conditions of existing hydrate-bearing sediments. (C) 2017 Elsevier Ltd.