The abundance and locations of the natural gas hydrate reserves covers all continents. The source of the methane can be either the microbial degradation of organic matter in shallower sediments or deeper-seated thermogenic methane accumulations. Thermodynamic stability of the hydrate is sensitive to local temperature and pressure but all components in the hydrate have to be in equilibrium with the surroundings if the hydrate is to be thermodynamically stable. Natural gas hydrate accumulations are therefore rarely in a state of complete stability in a strict thermodynamic sense.