| Groningen | |
|---|---|
| Country | Netherlands |
| Region | Groningen |
| Location | Slochteren |
| Offshore/onshore | onshore |
| Operator(s) | Nederlandse Aardolie Maatschappij BV |
| Field history | |
| Discovery | 1959 |
| Start of development | 1959 |
| Start of production | 1963 |
| Production | |
| Current production of gas | 3,300 million cubic feet per day (93×106 m3/d) |
| Current production of gas (million cubic meters per day) | 93 |
| Estimated gas in place | 100,000 billion cubic feet (2,800×109 m3) |
| Estimated gas in place (billion cubic meters) | 2800 |
The Groningen gas field is a giant natural gas field located near Slochteren in Groningen province in the northeastern part of the Netherlands. Discovered in 1959, it is the largest natural gas field in Europe and the tenth largest in the world.[1]
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After two previous unsuccessful wells were commissioned to search for oil and gas, on July 22, 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.[2] 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.[1][2] As of 2009[update] the Groningen gas field has produced around 1,700 billion cubic meters (60.7 trillion cubic feet) which represents 60% of the total reserves of the field but the remaining 1,100 billion cubic meters (39.3 trillion cubic feet) are expected to last for another 50 years.[3]
The Groningen gas field is operated by the Nederlandse Aardolie Maatschappij BV (NAM), a joint venture between Royal Dutch Shell and ExxonMobil with each company owning a 50% share.[3] The field accounts for 50% of the natural gas production in the Netherlands, the other 50% being supplied by around 300 smaller gas fields, most of them located offshore in the North Sea.[4]
The Groningen field lies within the Southern Permian Basin, which extends from the eastern coast of England to Poland. Within this area large volumes of gas have been discovered, mainly reservoired in the Rotliegend sandstone, with producing fields in England, the Netherlands, Germany, Denmark and Poland. [1]
The main reservoir in the Groningen field is the Cisuralian (Lower Permian), Rotliegend Slochteren sandstone. The Rotliegend reservoir at Groningen is mainly an aeolian sand with local development of fluvial wadi sands.[1]
Porosities lie generally in the range 15–20% with permeabilities in the range 0.1–3000 mD.[1]
The main source rock for the gas at Groningen are coals and carbonaceous shales within the Westphalian coal measures sequence that lies unconformably beneath the Rotliegend.[1] These sources are dominated by type III kerogen.[5]
The Groningen structure is a NNW-SSE trending intrabasinal high formed by normal faulting during the Mesozoic, particularly during the Late Jurassic to early Cretaceous.[1] It has an overall horst geometry, lying between the Ems Graben to the east and the Lauwerszee Trough to the west.[6]
The Rotliegend is covered by the Late Permian Zechstein evaporite sequence, consisting of carbonate, anhydrite and halite, which provides an effective seal to the gas accumulations within the underlying sandstone.[1]