Favorable geological conditions in Germany make it possible to store gas on a large scale and with the least possible intervention in nature and landscape – at the same time economically and environmentally compatible. Storage in subterranean naturally created or artificially created cavities is a long established technology. Different types of gas storage can be distinguished here.
Natural gas storage facilities can initially be divided into two types: aboveground and underground storage. With their small storage capacity, the smaller aboveground plants hardly contribute and are merely used to balance short-term demands.
To compensate the fluctuating gas consumption on a larger scale larger underground storage is required. They are used to compensate for seasonal fluctuations in consumption and for large peak loads. Two types of underground storage exist: on the one hand artificial cavities in salt mines, so-called cavern storage, on the other hand naturally occurring porous spaces such as water-bearing aquifers or former gas and oil reservoirs in permeable rock formations. They are called pore storage. The two storage types differ with respect to the storage rock and the storage mechanisms. They can be situated in depths of a few hundred up to two thousand meters.
Cavern storage facilities consist of large caverns created by the targeted solution mining of salt formations. This process gives the caverns a cylindrical shape. They may have diameters of up to 100 metres, with heights ranging from 50 to 500 metres and geometric volumes of up to 800,000 cubic metres. The petrochemical properties of the salt ensure that the gas is sealed in naturally; there is therefore no need for an additional lining. At depths between 800 and 1,500 metres, gas can be stored at pressures of up to 200 bar.
The properties of cavern storage facilities not only allow the storage of large quantities of gas but also mean that gas can be rapidly injected and withdrawn from storage. These storage facilities are therefore especially well-suited for compensating for severe short-term demand fluctuations.
In porous rock storage facilities, the natural gas is stored at high pressure in an underground storage formation. These storage facilities are mainly developed in aquifers, water-bearing sandstone formations with appropriate geophysical properties such as high permeability. Apart from these water-bearing formations, depleted oil and natural gas fields may also be used for storage. In this case, the suitability of the formation for gas storage has already been demonstrated by nature. These facilities feature gas-impermeable caprock and ensure naturally gas-tight storage.
Porous rock storage facilities are used for storing large quantities of gas but, as a result of their geophysical properties, the maximum injection and withdrawal rates are relatively low. Natural gas stored in facilities of this type is therefore used mainly to compensate for seasonal fluctuations in gas demand.
Further technical and commercial information on gas storage in Germany can be found on the websites of our member companies.