Formation Conditions of Natural Gas Hydrates
Natural gas hydrates, also known as methane hydrates, are a type of solid fuel source found all over the world, but especially in permafrost, deep-ocean sediment, and in some kinds of producing reservoirs for oil and gas wells. This type of gas hydrate forms when methane gas molecules become trapped within a lattice structure composed of crystalline ice. In order for any gas hydrate to form, three main environmental factors must exist: pressure, temperature and the availability of methane.
Pressure
One of the most critical factors in natural gas hydrate formation is pressure. Natural gas hydrates typically form at pressures which are greater than the hydrostatic pressure. The higher the pressure, the higher the temperature at which natural gas hydrates are able to form. While all hydrate-forming gases require higher pressures for formation than the hydrostatic pressure, the exact pressure required for any particular gas is dependent on its form. For methane, the minimum pressure to form hydrate is typically between 20-30MPa. High pressure environments such as the deep ocean and within the Earth’s interior above active tectonic-plates are more likely to have natural gas hydrate formation.
Temperature
The temperature of the environment also plays an important role in the formation of natural gas hydrates. For methane, the temperature should generally be between 0-30°C. This relatively low temperature range is beneficial, since it means that the methane is more likely to remain in its ice-like form until it is either burned or destabilized by an external force.
Methane Availability
As with any type of gas, the availability of methane is an important factor in the formation of natural gas hydrates. If there is not enough methane in the environment, or if it is not evenly distributed throughout the area, then it will be harder for hydrate formation to take place. For this reasons, methane-rich environments such as planetary depths and natural gas reserves are optimal for natural gas hydrate formation.
Overall, natural gas hydrates can form in a variety of environments, provided that three main environmental factors are in place: pressure, temperature and methane availability. The deeper the environment, the higher the pressure and the lower the temperature, the more likely natural gas hydrates will form. This makes the deep ocean and areas with large natural gas reserves ideal for hydrate formation.
