Technical description of the storage
Stenlille Gas Storage Facility is an aquifer storage facility. The gas is stored in water filled sand beds which lie approximately 1,500 metres below the ground surface. Over the sand beds there are approximately 300 metres of gas tight clay beds, which have a slightly domed structure forming a basin. The clay layer ensures that the gas does not penetrate up to the surface.
When gas is pumped into the sand layers via the production wells in the hot part of the year, 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 drawn up from the gas storage facility in the cold part of the year, 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 drawn up again without mechanical power being required.
Stenlille Gas Storage Facility consists of a central facility and three well sites. Fourteen production wells have been installed at the three well sites. These are used to pump the gas down into the subsurface and to draw it up 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 Gas withdrawn from the subsurface is also cleaned of water particles etc, before the gas pressure is reduced and it is distributed via the transmission network.