The Groningen field is Europe's biggest gasfield. Supplying low caloric gas to households, buildings and greenhouses for heating in the Netherlands, and parts of Germany, Belgium and France. It is operated by Shell, in a joint venture with Exxon Mobile and Dutch State company EBN.
On 22 July 1959, the Slochteren 1 well, drilling to a depth of 3,000 metres (9,800 ft), discovered the huge 2.8 trillion cubic meters (100 trillion cubic feet) gas field in the porous Rotliegend sandstone formation, which is 130 metres (430 ft) to 140 metres (460 ft) thick and 45 kilometres (28 mi) long from north to south by 25 kilometres (16 mi) long from east to west. The field started production in 1963 and produced around 100 billion cubic meters (3.57 trillion cubic feet) per year in the first decade of production but gradually the annual production fell to around 35 billion cubic meters (1.25 trillion cubic feet) per year. Since 1986 earthquakes are felt in Groningen. At first Shell denied any link with the gasfield, but after a few years they acknowledged that the depletion of the gasfield might cause 'minor tremors' In 2012 a 3.6M earthquake occurred. The Dutch Mining Authority ordered that gas production should be shut in 'as much as possible and as quickly as possible' . The year after production was ramped up to 54 BCM. In succeeding years political pressure, court cases and actions managed to cap in production at 24BCM (2017). Experts suggest 12BCM would be a safe upper limit, but several groups are campaigning to shut down the gas field completely. The earthquakes are caused by the depletion of the field. The field pressure has dropped so much that the formation is shrinking. Causing a lowering on surface level of about 1 meter over the long run, and over a 1000 small earthquakes. Although at a low level on the Richter scale they cause a huge amount of damage. They come from a low depth (3km) , are frequent and are amplified by the clay surface. The Netherlands is still the EU's biggest gas producer. Next to the Groningen gas field there are 250 smaller gas fields, mainly supplying high caloric natural gas.