January 03, 2021

In 1959, a large gas field was discovered in Slochteren, a village in the province of Groningen located in the northern Netherlands. The gas field was discovered by the Dutch oil company Nederlandse Aardolie Maatschappij (NAM) when searching for oil.
When, in 1952, one of the first wells drilled in the northern part of the Netherlands, Harkstede, found traces of gas in Lower Permian sands, there was little rejoicing. The target had been the Upper Permian Zechstein formation and the drillers were looking for oil. The next well, TBR-1, drilled in 1955, also failed to find oil in the Zechstein, and bottomed out before reaching the Lower Permian.
So when on July 22nd, 1959, Slochteren 1 discovered large quantities of gas in the Lower Permian Rotliegend formation, there was simply satisfaction that there appeared to be enough gas to be commercial. Similar emotions were felt when Slochteren 2, 30km to the SE, also found gas in the Rotliegend.
Only when a further well, drilled 20 km north-east of Slochteren near Delfzijl, the significance of these discoveries was realised. Eventually, the field would prove to cover an area of 900 km2 and hold a massive 99 Tcf (2,800 Bm3) of recoverable gas.
The production of gas from this field started in 1963. Since its discovery the estimations of its size have been adjusted upwards frequently. In 1959 the size was estimated at about 60 billion m3, in 1962 it was estimated at 470 billion m3 rising to 2000 billion m3 in 1967 to end up at an astonishing estimated total size of 2800 billion m3.
The discovery of natural gas was the start of a revolution in the European heating market. However, the size of Groningen is not its primary significance. More important is the significance of the discovery to the oil industry and to Europe at the time, and the lessons which have been learnt from it, both through efficiently extracting the gas and exploiting the resource over time.
The Southern Permian Basin, also known as the Central European Basin, is Europe’s largest sedimentary basin. The basin stretches across the southern part of the North Sea. It is connected to the Northern Permian basin by the Central Graben, midway between the British and Norwegian Coasts. The Southern Permian Basin evolved from Late Carboniferous to Recent times, and extends from eastern England to the Belarussian-Polish border and from Denmark to Southern Germany.
Up until 1959, the North Sea had been written off as a possible site for major hydrocarbon discoveries. In fact, when the eminent geologist George Lees had presented a paper to the Geological Society of London in 1936, suggesting oil could be found in Britain, he was virtually laughed out of the room, and there had been relatively little interest in the idea since then. But Groningen changed all that, as the existence of such a vast resource on the edge of continental Europe obviously begged the question: could the play extend into the North Sea?
Ultimately, the discovery opened up the whole of the North-West Europe to the hydrocarbon industry, both on and offshore. Many countries were not prepared for this, and legislation had to be rushed in, including methods of demarcating the offshore boundaries between nations, while systems for leasing acreage for exploration had to be defined. Nevertheless, a mere ten years after the discovery of Groningen virtually the whole of the southern North Sea below 58°N had been opened for hydrocarbon exploration.
In 1964, five years after the Groningen gas field discovery, the jackup Mr Louie drilled the first well in the North Sea. In December 1965 the Sea Gem discovered the first North Sea gas off the mouth of the River Humber.
The West Sole gas field was discovered BP in 1965. The field located at 43 miles off the coast of Yorkshire, was the first to be developed in the North Sea. West Sole produced its first gas in 1967.
The Leman gas field located 30 miles north-east of Great Yarmouth was discovered in August 1966.
Despite the many discoveries made since 1959, Groningen remains the biggest field in Europe and about the tenth largest in the world. In comparison Troll, the largest offshore gas field in the North Sea, discovered in 1979, had original reserves of 1,325 Bm3.
The effect of Groningen gas on the economy of the Netherlands was rapid and immense. Within a few years, a network of pipes had spread across the country and the majority of houses had been converted to natural gas as their main energy source.
The Groningen gas contains a relatively high part of Nitrogen (14%) and a lower amount of energy per m3 than most other gas. This is why it’s called low calorific gas.
More than 75% of the gas has already been produced since 1963 and has played a large role in the Dutch economy and welfare since then. Not only around 93% of the Dutch population utilized this gas for their stoves and boilers, but also large parts of the German, Belgian and Northern-France population
After protests in Groningen because of the increase in induced earthquakes, whose event count shows an exponential growth in time, the Dutch government decided on 17 January 2014 to cut output from the gas field and pay those affected by the earthquake a compensation worth 1.2 billion Euro, spread over a period of 5 years. The ministry said production would be cut in 2014 and 2015 to 42.5 bcm (billion cubic metres) and in 2016 to 40 bcm.
On March 29, 2018 the Dutch government announced it would shut down the gas extraction entirely by 2030 for safety reasons.
In September 2019 a further acceleration of the decommissioning of the field, stopping all regular production in 2022
(Source: E&C Consultants/Geoexpro/Wikipedia/AAPG/Bekaert – Image: Drilling rig near Slochteren in 1959/GeoExpro)