Ekofisk

from Wikipedia, the free encyclopedia
Ekofisk (North Sea)
Ekofisk
Ekofisk
Platforms on the Ekofisk complex

Ekofisk is an oil and gas field on Norway's continental shelf in the central North Sea . With estimated reserves of 3.8 billion barrels, it is the largest oil field in the North Sea after Statfjord . The discovery of the Ekofisk field in 1969 triggered the oil boom in the North Sea. The current operator is ConocoPhillips Skandinavia AS , other members of the Ekofisk consortium are Total , Norsk Agip , Norsk Hydro and Statoil . The field is located about 270 kilometers from the mainland coast in the Central Graben and just north of the border between the Norwegian and Danish sectors of the North Sea.

geology

The North Sea floor above the Ekofiskfeld is 70 to 74 meters deep, is comparatively flat and consists of fine sand. The Ekofisk plants extract the oil primarily from the Ekofisk layer, a rock layer at a depth of around 3000 to 3500 meters. It is made of secondary chalk . The coccolith deposits from the late Cretaceous period were eroded in the Cenozoic and then settled in today's Ekofisk area. Impermeable claystone was deposited over the layer of chalk, which prevented the water bound in the chalk and later the oil from moving upwards. The pressure in the rock pores is 1.4 times the normal pressure at this depth, and the reservoir temperature is around 130 degrees Celsius.

The pressure made sure that the pores remain open. Today the porosity is almost 50 percent, i.e. half of the chalk layer consists of pores . Similar rocks have a porosity of 3 to 40 percent, with 10 to 20 percent being the norm and 40 percent being a rare exception. The chalk developed a high level of permeability through a salt dome below the stuck chalk . The salt dome stretched over time from , pressed the chalk upwards, set off numerous pores in this movement and were associated with each other. This exceptionally high permeability allows good permeability to the crude oil, which contributed to the suitability of the Ekofisk formation as an oil reservoir.

Since 1985, the soil in the Ekofisk field has been sinking about half a meter per year due to oil production. The micropores created by the overpressure close after the oil has been pumped out. This decrease is the most pronounced in the North Sea development area and was not foreseen. In order to continue to guarantee the safety of the drilling rigs before a wave of the century , the central drilling rig had to be subsequently increased in a complex and costly manner. As the subsidence continued, new platforms were built.

As hydrocarbons were produced and replaced with water, the chalk began to dissolve due to microscopic high pressure intergranular compounds and reformed into a more compact, less porous structure. A movement of several meters was detected. Calculations by Phillips Petroleum showed that at the end of the compression phase a subsidence of almost 6 meters had to be expected. The Norwegian government urged Phillips to take action. The French consultant TECHNIP was commissioned to find a solution.

Since 5 of 7 platforms were connected to each other, they had to be raised about 6 meters at the same time. The solution was to extend the tubular steel legs of the platforms. After the load of the 5 platforms had been shifted to the lifting devices, about one meter was separated from the legs and a flange was welded to the upper and lower end. In this way, the 5 platforms could be raised about 6 meters at the same time in a large-scale operation and then extension tubes could be inserted. After screwing the flanges together, the platforms were safe and stable again.

The 4-day campaign was completed on August 17, 1987 at 11:30 am thanks to 108 hydraulic cylinders synchronized with a network of 14 NUM-760 CNC controls. The position tolerance between the cylinders (3 millimeters for the 6 meter lift per platform and a maximum of 100 millimeters between the platforms) had to be maintained for 38 hours. A few days earlier, the hotel platform, which was not connected to the other platforms, was raised. The total load capacity of all cylinders was approximately 40,000 tons and was published in the Guinness Book of Records as the greatest salvage work.

history

Production rates of Norwegian oil fields 1971 to 2003. Ekofisk is symbolized by light blue.

The Phillips Petroleum Company discovered the field on December 23, 1969, making the first successful exploratory well in the North Sea. After the development, production began in 1971. Ekofisk is currently Norway's most important oil deposit and, after the Statfjord field, the largest oil deposit in Norway. It was declared a national cultural monument in 2001. The Ekofiskfeld was part of the first licensing round in Norwegian waters. This was one of the two rounds that took place without direct state influence and the only one that was run entirely by private companies.

With the construction of the Ekofisktank in 1971, a new generation of drilling rigs began. It was an oil silo, constructed similar to a grain silo , which was divided into nine areas and reached a height of 90 meters on a floor area of ​​50 meters × 50 meters. It was surrounded by a breakwater 95 meters in diameter. The cement construction was made in the deep but protected water of a fjord from prefabricated sections that were placed on the floating foundation.

Since the Norwegian state did not allow the flaring of natural gas , Philipp Petroleum signed a contract in 1973 with a consortium made up of Ruhrgas , Gaz de France , Distrigas and Gasunie , who undertook to purchase all natural gas from the field at a price that was directly linked to the price of oil was. A short time later, an identical contract was concluded between the same parties for the neighboring Eldfisk field. The gas pipeline that brings the gas to the continent is the Europipe across the Lower Saxony Wadden Sea to Emden . Since 1980, the field has been connected to the Seal Sands refinery on the north bank of the Tees in northern England with a nearly 350-kilometer pipeline .

At the beginning of the 2000s, the Norwegian Oljedirektoratet investigated whether an enhanced oil recovery would be worthwhile in the Ekofisk and Gullfaks oil fields . However, it came to the conclusion that the technology would only be economical at an oil price between 22 and 33 USD / barrel, while industry estimates at that time predicted an oil price of 27 to 33 USD / barrel for the future. The project was then rejected.

Accidents

The field was the scene of several serious accidents.

On April 22, 1977, one of the largest ever blowouts in an offshore oil field occurred on Ekofisk Bravo . In seven days, 23,000 tons of crude oil flowed into the North Sea and spread over an area of ​​40,000 km². Seabirds were the main victims, while other marine organisms suffered little damage.

A few years later the biggest disaster in offshore oil production up to that point occurred when the platform " Alexander L. Kielland " capsized on March 27, 1980 , killing 123 people.

A monster wave hit the "Two-Four-Delta" platform in its second year of existence. The 30-meter wave cost no lives as the Two-Four-Delta was still under construction, but a larger part of the substructure suffered permanent damage.

Environmental impact

The Ekofisk field was one of the first to study the effects of oil rigs as artificial reefs . Attempts at fishing with lines and nets in the late 1970s showed remarkable concentrations of cod in close proximity to platforms. Their rates halved at distances of 50, 100 and 200 meters from the platforms. The researchers attributed the increased cod stocks to high krill rates, which were likely to accumulate near the platforms due to artificial lighting and changes in current.

See also

Individual evidence

  1. ↑ Joseph Hilyard (Ed.): 2008 International Petroleum Encyclopedia. PennWell Books, 2008, ISBN 978-1-59370-164-2 , p. 339.
  2. ^ John S. Gray, Michael Elliot: Ecology of Marine Sediments: From Science to Management , Oxford University Press US, 2009, ISBN 978-0-19-856902-2 , p. 59.
  3. ^ A b c Ivar B. Ramberg: The making of a land: geology of Norway. Geological Society, 2008, ISBN 978-82-92394-42-7 , p. 430.
  4. ↑ Allain van Cotthem: Eurock 2006: multiphysics coupling and long term behavior in rock mechanics Taylor & Francis, 2006, ISBN 0-415-41001-0 , p. 429.
  5. ^ Ian Lerche: Inverse and risking methods in hydrocarbon exploration: a compendium. multi-science publishing, 2005, ISBN 0-906522-32-3 , p. 67.
  6. ↑ BA Schrefler: Environmental geomechanics. Springer, 2001, ISBN 3-211-83680-2 , p. 238.
  7. ↑ Special Ekofisk. (PDF; 628 kB) (No longer available online.) NUM, October 1, 1987, pp. 1–2 , formerly in the original ; Retrieved January 26, 2011 .  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Dead Link / docs.niaag.net  
  8. ^ Rögnvaldur Hannesson: Investing for sustainability: the management of mineral wealth. Springer, 2001, ISBN 0-7923-7294-8 , p. 80.
  9. ^ A b Energy Charter Secretariat: Putting a Price on Energy. Energy Charter Secretariat, 2007, ISBN 90-5948-046-5 , pp. 159-162.
  10. ^ Mike Chrimes: Historic Concrete: Background to Appraisal. Thomas Telford, 2001, ISBN 0-7277-2875-X , p. 296.
  11. ↑ Michael Stratton, Barrie Stuart Trinder: Twentieth century industrial archeology Taylor & Francis, 2000, ISBN 0-419-24680-0 , p. 86.
  12. ^ Simon Shackley, Clair Gough: Carbon capture and its storage: an integrated assessment Simon Shackley, Clair Gough p. 248.
  13. ↑ Lawrence R. Walker: Elsevier, 1999, ISBN 0-444-82420-0 Ecosystems of disturbed ground p. 68.
  14. ↑ Archive link ( Memento of the original dated December 3, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / home.versatel.nl
  15. ↑ Craig B. Smith: Extreme waves. National Academies Press, 2006, ISBN 0-309-10062-3 , p. 8.
  16. ↑ Antony Jensen et al .: Artificial reefs in European seas Springer, 2000, ISBN 0-7923-6144-X , p. 334.

Web links

Commons : Ekofisk  - collection of images, videos and audio files

Coordinates: 56 ° 32 '9 "  N , 3 ° 11' 55"  E