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About Gas Storage Denmark
Last updated on 31. October 2016
Gas Storage Denmark owns and operates two storage sites. One in Stenlille in the middle of Zealand, and one in Lille Torup in the northern part of Jutland. The two storage facilities are operated as one common storage point.
Stenlille
 
Stenlille Gas Storage Facility is an aquifer storage facility. The gas is stored in water-filled sand beds which lie approximately 1,500 m below the ground surface. Above the sand beds are approx. 300 m of gas-tight clay beds, which have a slightly domed structure forming a basin. The clay layer ensures that the gas does not penetrate to the surface.
 
When gas is pumped into the sand layers via the production wells during the summer, the water is forced downwards and outwards to the sides. The gas, which always is in the gaseous state, lies at the top of the sand layer. When the gas is extracted from the gas storage facility during the winter, the water in the aquifer acts as a spring, which also rises up again as the gas bubble becomes smaller. This ensures that the gas can be extracted again without the need for mechanical power.
 
Stenlille Gas Storage Facility consists of a central facility and three well sites. 14 production wells have been installed at the three well sites. These are used to pump the gas down into the subsurface and to extract it again. The well sites are connected to the central facility via large gas pipelines.
 
There are compressors at the central facility, which increase the gas’s pressure before it is sent down into the subsurface. Gas withdrawn from the subsurface is also cleaned of water particles etc., before the gas pressure is reduced and it is distributed via the transmission network.


Lille Torup
 
The Lille Torup gas storage facility has seven gigantic cavaties called caverns at a depth of 1.2 and 1.5 km in a large subterranean salt dome. The height and diameter of the salt dome is 5 km, and the top is 300 m below the ground surface. The process facility and the control room are located above ground, and technicians and storage personnel control that operations are safe and stable.
 
In the salt dome, the seven 200-300 m high and 50-65 m wide caverns have been flushed with water from Hjarbæk Fiord. The size of the caverns corresponds to three and a half football fields end to end. The inside of the caverns is not of uniform round and smooth shape, but the structure is rough and uneven. The salt from the seven caverns has been discharged into the Liim Fiord at Lovns Bredning so diluted that it has not posed a threat to the environment. It takes 2-3 years to flush a cavern, and a total of some 8 million tonnes of pure salt have been discharged at Lille Torup.
 
The caverns have subsequently been pumped up with natural gas. In principle this corresponds to seven enormous gas cylinders. The salt in the dome is plastic, and this ensures that the gas remains in the caverns and that it only gets out through the pipes to the storage facility. The maximum pressure is 150-200 bar when the caverns are full. Together the caverns hold gas for approximately two months’ consumption. The caverns can be ‘reflushed’ after 10-20 years of storage operation to compensate for the shrinkage that has taken place.
 
The seven caverns have names from the Nordic mythology: Heimdall, Tyr, Idun, Frey, Freya, Brage and Balder

Contact

Mads Vejlby Boesen+4530674727Send mail
Mads Vejlby Boesen

Facts

Different types of facilities
Today it is possible to store natural gas in four types of subterranean storage facilities:
  • Cavities blasted in rock
 
  • Empty oil and gas fields
 
  • Cavities flushed in salt layers (such as the Lille Torup gas storage facility)
 
  • Waterlogged layers of sandstone (Stenlille natural gas storage facility)
 
Other international facilities
There are about 100 cavernous gas storage facilities around the world today.