North Sea oil

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North Sea Oil Platforms
North Sea Oil Platforms

North Sea oil refers to oil and natural gas ( hydrocarbons) produced from oil reservoirs beneath the North Sea.


North Sea oil was discovered in the early 1960s, with the first North Sea oil coming on line in 1971 and being piped ashore at Teesside, England, from 1975, but the fields were not intensively exploited until rising oil prices in the 1980s made exploitation economically feasible. Inaccessibility and dangerous conditions offshore require complex and expensive production methods.

In reality, oil seeps had been known from coal beds on either side of the North Sea, but only a limited amount of development had occurred ( Eakring oil field, Nottinghamshire, England; Edinburgh Oil Shales (which seem unrelated to later discoveries); and small discoveries in the Netherlands and Northern Germany). A "demonstration well" was sunk in 1938 in association with the "World Petroleum Congress" at The Hague. After the Second World War a small number of onshore gas and oil fields were found in In 1959, an academic well drilled at Ten Boer near Groningen, Netherlands was deepened and discovered a significant gas deposit. Appraisal and development wells over the next few years brought the realisation in 1963 that the Groningen field was not just "economic", nor even "big", or "large", or "giant", but was an "elephant" field of huge potential. Given that, extending exploration into adjacent areas was a "no-brain" decision.

The exploration of the North Sea has been a story of continually pushing the edges of the technology of exploitation (in terms of what can be produced) and later the technologies of discovery and evaluation ( 2-D seismic, followed by 3-D and 4-D seismic; sub-salt seismic; immersive display and analysis suites and supercomputing to handle the flood of computation required).


There are five countries with North Sea Production. All operate a tax and Royalty licencing regime. The respective sectors are divided by median lines agreed in the late 1960s:

  • United Kingdom - licences are administered by the DTI ( Department of Trade and Industry- Website). The UKCS is divided into quadrants of 1 degree latitude and one degree longitude. Each quadrant is divided into 30 blocks measuring 10 minutes of latitude and 12 minutes of longitude. Some blocks are divided further into part blocks where some areas are relinquished by previous licensees. For example block 13/24a is located in quad 13 and is the 24th block and is the a part block of this block. The UK government has traditionally issued licences via periodic (now annual) licensing rounds. Blocks are awarded on the basis of the work programme bid by the participants. The UK DTI has been very active in attracting new entrants to the UKCS via Promote licencing rounds (less demanding terms) and the fallow acarage initiative where non-active licences have had to be relinquished.
  • Norway - licences are administered by the NPD (Norwegian Petroleum Directorate Website in English ). The NCS is also divided into quads of 1 degree by 1 degree. Norwegian licence blocks are larger than British blocks, being 15 minutes of latitude by 20 minutes of longitude (12 blocks in a quad). Like Britain there are numerous part blocks formed by relicensing relinquished acreage.
  • Denmark - The Danish sector is administered by the Danish Energy Authority ( website in English). The Danes also divide their sector of the North Sea into 1 degree by 1 degree quadrants, their blocks however are 10 minutes latitude by 15 minutes longitude. Part blocks exist where partial relinquishments have taken place.
  • Germany - Germany and the Netherlands share a quadrant and block grid - quadrants are given letters rather than numbers. The blocks are 10 minutes latitude by 20 minutes longitude. Germany has the smallest sector in the North Sea.
  • Netherlands - The Dutch sector is located in the Southern Gas Basin and shares a grid pattern with Germany.

Reserves and production

The North Sea contains the majority of Europe's oil reserves and is one of the largest non- OPEC producing regions in the world. While most reserves lie beneath waters belonging to the United Kingdom and Norway, some fields belong to Denmark, the Netherlands, and Germany.

Most oil companies have investments in the North Sea. Peaking in 1999, production of North Sea oil was nearly 6 million barrels (950,000 m³) per day. Natural gas production was nearly 10 trillion cubic feet (280,000,000 m³) in 2001 and continues to increase.

Brent crude (one of the earliest crude oils produced in the North Sea) is still used today as a standard reference for pricing oil.

North Sea oil production fell ten percent (230,000 barrels) in 2004, and fell an additional 12.8% in 2005. This was the largest decrease of any other oil exporting nation in the world, and has led to Britain becoming a net importer of crude for the first time in decades, as recognized by the energy policy of the United Kingdom. . The production is expected to fall to one-third of its peak by 2020.

List of areas ("plays")

A play is a collection of fields or structures with common features of source rock, thermal history, trap style and structure that make lessons from the discovery and development of one field on a play closely applicable to other similar structures. In stratigraphic order:


  • Devonian Old Red Sandstone - see Buchan oil field

Carboniferous and Permian

  • Sub-Zechstein Gas - Gas fields sourced from the Carboniferous Coal Measures and reservoired in the Permian Rotliegend sandstone or Carboniferous sandstones in the Northern part of the Southern Gas basin. Zechstein dolomite reservoirs alos exist (e.g. Auk oilfield) . Seals are from Zechstein (also of Permian age) halite beds. Structures are mostly due to rifting in the pre-salt section. Example field - the discovery for the entire province at Groningen, Netherlands.


The Triassic play is located in the Central North Sea. The reservoir is composed of fluvial and lacustrine sandstones of the Skaggerak formation. Fields with Triassic reservoirs include J-Block (Judy, Jade, Joshephine) and Marnock

Triassic reservoirs are also important in the East Irish Sea (Morecambe gas field, Sherwood Sandtsone) and Southern North Sea (Hewett gasfield complex - Bunter sandstone)

Middle Jurassic

Northern North Sea tilted fault blocks; Brent Series deltaic sands of Bathonian age. In 1971 the Shell/ Esso joint venture drilled a poorly resolved structure in block 211 and found a classical prograding delta sand sequence (the Brent Sands overlain by a good source rock (the Kimmeridge Clay Formation, broke up into tilted fault blocks due to crustal extension, and the whole sealed by the lateral equivalent of the Chalk, the muddy Shetland Group. Several billion barrels of oil later, the Brent Field is being depressurised in the mid 2000s with shutdown looming on the horizon. Economically, this is the major play in the North Sea.

Upper Jurassic

  • Upper Jurassic Central North Sea, Fulmar Play - The Oxfordian Age Fulmar sandstone is a shallow marine unit present in the southern part of the Central Graben. It is also present in the Norwegian sector where it is called the Ula formation. This reservoir is very good quality with high porosities which can be preserved under deep (6000m) burial in high pressure high temperature (HPHT) fields such as Elgin, Franklin and Shearwater.
  • Upper Jurassic Turbidites - These Kimmeridgian/Volgian sandstone reservoirs are found in the Outer Moray Firth. The Buzzard Field, the largest discovery in recent years has an Ettrick formation turbidite reservoir.
  • Fanglomerates against faults. In the late 1980s seismic along some of the major "bounding faults" of the main basins of the North Sea revealed wedges of sediment which evidently piled up while the faults were still moving ( syndepositional faulting). Magnus, Tiffany, Toni and Thelma follow this play, with many smaller developments being developed along-strike since as sub-sea tie-back technology develops

Lower Cretaceous

The Lower Cretacous play developed in the 1980s and 1990s. The reservoir rocks are Aptian / Albian turbidites. Most discoveries are stratigraphic traps . Examples include the Britania gas field and the Blake oil field

Upper Cretaceous

Chalk oil - The first major oil discovery was in 1969 by Phillips in the Ekofisk field of the Central North Sea (56°30'N 3°10'E). Source is Kimmeridge Clay Formation. Oil and gas generated early after deposition invaded the Cretaceous Chalk sediments and displaced the water necessary for compactional diagenesis (with later consequences). Structures are broad anticlines cored either by salt diapirs or Pre-Cretaceous Horsts.


Central North Sea Tertiary turbidite sand fans - the Forties field (57°45'N 01°E) targeted a series of sand fans in mudstone surrounds and capped by Palaeocene Basalts. Source was Kimmeridge Clay Formation again. The Forties was discovered the year after Ekofisk, following several years of frustration in failing to adequately resolve these structures and find a major field.

  • Over-salt Sands. In the Central North Sea a large number of salt domes could early be seen to penetrate from the Zechstein up into the Tertiary cover rocks, but without adequate seismic they weren't considered good targets for development. Better seismic allows the development of numerous small fields around or above these structures. Individual fields are mostly small, but can be accommodated by tie-ing the fields back to existing facilities. Tie-in pipelines and control umbilicals of over 10 km are not unknown, despite serious technical difficulties (such as plugging of lines with methane hydrates or the rock stresses associated with piercement diapirs.)

List of fields

South to north.


    • Onshore
      • Rijswijk oil field - An Oilfield with a Lower Cretaceous reservoir
      • Schoonebeek - largest onshore oilfield in Western Europe
      • Groningen gas field - huge gas discovery
    • Offshore (serviced from The Hague
      • Zuidwal
      • Ameland - (whether this will be developed onshore of offshore is an open question)
      • Many fields in Quadrantrs P, Q, K, L, some in blocks E, F

United Kingdom

Reference DTI Brown book

    • Onshore
      • Wytch Farm - BP's largest onshore development
      • Singleton, West Sussex - beautifully situated across the valley from Goodwood Racecourse
      • (several other prospects along strike on the South Downs)
      • East Midlands oilfield, centred on Eakring, Nottinghamshire, and extending up to Eskdale, North Yorkshire and the Pickering / Kirkby Misperton structure under Ryedale.
    • Offshore (Southern North Sea) (serviced from Lowestoft, Monkey Town, Yarmouth and near Skegness)
      • Hewett - Triassic, operated by Tullow oil
      • Dotty - Triassic
      • Leman - Rotliegend
      • Vulcan - Rotliegend, operated by ConocoPhillips
      • Indefatigable - Rotliegend
      • Viking - Rotliegend - operated by ConocoPhillips
      • Audrey - Rotliegend - operated by ConocoPhillips
      • Ann - Rotliegend - operated by ConocoPhillips
      • Amethyst -Rotliegend -operated by BP
      • West Sole gasfield -Rotliegend
      • Rough gasfield - used for Natural gas storage
      • Cleeton gasfield - Rotliegend
      • Ravenspurn gasfield - Rotliegend
      • Caister gasfield - Carboniferous sandstone, - operated by ConocoPhillips
      • Murdoch gasfield- Carboniferous sandstone, - operated by ConocoPhillips
      • Gordon gasfield - Triassic
      • Forbes gasfield - Triassic
      • Esmond gasfield - Triassic
    • Offshore Irish Sea Serviced from Liverpool, Blackpool and Morecambe
      • Douglas gas field - Triassic, operated by BHP
      • Lennox gas field - Triassic, operated by BHP
      • Hamilton gas field - Triassic, operated by BHP
      • Morecambe gas field - Triassic, Operated by Centrica
      • Millom gasfield - Triassic, operated by Burlington Resources
    • Offshore (Central North Sea) (serviced from Aberdeen
      • Argyll oilfield - Rotliegend / Zechstein
      • Auk oilfield - Rotliegend / Zechstein, Operated by Shell Oil
      • Clyde oilfield - Fulmar sandstone operated by Talisman Energy
      • Fulmar oilfield - Fulmar sandstone, Operated by Shell Oil
      • J-Block gasfield - Triassic, Chalk and Palaeocene, operated by ConocoPhillips
      • Elgin and Franklin gasfields - Fulmar sandtone and Middle Jurassic, operated by Total S.A.
      • Shearwater Gasfield - Fulmar - operated by Shell oil
      • Erskine gasfield -Middle Jurassic sandstone - operated by Chevron
      • Gannet oilfield (A, B, C, D, E, and F) - Paleocene and Jurassic - operated by Shell
      • Scoter oilfield -operated by Shell
      • Pierce oilfield - Paleocene (non-horizontal Oil-Water Contact), Operated by Shell Oil
      • ETAP gas field comaplex includes Marnock, Machar, Monan and Mirren fields, Operated by BP
      • Arbroath oilfield - Plaeocene, Forties Sandstone, operated by Talisman Energy
      • Blane oil field - Paleocene, Forties Sandstone, operated by Talisman Energy
      • Montrose oilfield - Paleocene, Forties Sandstone, operated by Talisman Energy
      • Lomond gasfield - Palaeocene, Forties Sandstone operated by BP
      • Everest gasfield - Palaeocene, Forties Sandstone operated by BP
      • Armada gasfields - Palaeocene and Jurassic Fulmar, operated by BG Group
      • Kittiwake oilfield -operated by Shell
      • Nelson oilfield - Palaeocene, Forties Sandstone, Operated by Shell Oil
      • Forties oilfield - Palaeocene, Forties Sandstone operated by Apache Corp.
      • Brittania gasfield - Lower Cretaceous, Operated by ConocoPhillips and Chevron
      • Alba oilfield - Eocene operated by Chevron
      • Buchan oil field - Devonian Sandstone - Operated by Talisman Energy
      • Ettrick oilfield - Upper Jurassic
      • Buzzard oilfield - Upper Jurassic operated by Encana, largest discovery in last 10 years
      • Andrew oilfield - Palaeocene
      • Moira oilfield - Palaeocene
      • Maureen oilfield - Palaeocene (abandoned, platform removed was operated by Phillips Petroleum)
      • Cyrus oilfield - Palaeocene
      • Balmoral oilfield - Palaeocene
      • Gryphon oilfield- Eocene Operated by Maersk
      • Harding oilfield - Eocene Operated by BP
      • Tiffany oilfield - Upper Jurassic
      • Toni oilfield - Upper Jurassic (subsea tie back to Tiffany)
      • Thelma oilfield - Upper Jurassic (subsea tie back to Tiffany)
      • Sycamore oilfield - Upper Jurassic (subsea tie back to Tiffany and Brae)
      • Brae oilfield Upper Jurassic (several satellite accumulations) operated by Marathon Oil
      • Miller oilfield
    • Offshore (Moray Firth) (Serviced from Aberdeen)
      • Beatrice oilfield- Upper Jurassic operated by Talisman Energy
      • Unnamed, yet, Senergy
      • Claymore oilfield - Upper Jurassic operated by Talisman Energy
      • Piper oilfield - Upper Jurassic operated by Talisman Energy(produced from Piper Bravo platform after loss of Piper Alpha
      • Tartan oilfield - Upper Jurassic operated by Talisman Energy
      • Scott oilfield - Upper Jurassic operated by Talisman Energy
      • Ross oilfield - Upper Jurassic (small development by Talisman Energy; within sight of Peterhead)
      • Blake oilfield -Lower Cretaceous, operated by BG Group
    • Offshore (Northern North Sea) (serviced from Aberdeen)
      • Beryl oilfield upper Jurassic operated by ExxonMobil (with offshoots to Linhe, Ness...)
      • Bressay oilfield
      • Emerald oilfield
      • Strathspey oilfield (decommissioned? subsea tie-back to Ninian Central)
      • Columba oilfield (extended-reach drilling from Ninian platforms)
      • Ninian oilfield (3 platforms, including the dreaded "one legged, fire-breathing giant from Nigg", if you believe in Scotland's answer to Nostradamus, the Seer of Brathan)
      • Lyell oilfield
      • Heather oilfield Middle Jurassic operated by DNO
      • Brent oilfield Middle Jurassic operated by Shell (4 main platforms, plus the Brent Spar fiasco.)
      • Dunlin oilfield Middle Jurassic operated by Shell
      • Hutton oilfield (produced from the innovative Tension-leg platform; decommissioned 2001 was operated by Conoco)
      • Cormorant oilfield Middle Jurassic operated by Shell, (production started sweet, but has turned slightly sour over the decades. which is very interesting. And worrying.)
      • Tern oilfield Operated by Shell Oil (The 'Black Pig' to its friends. Captain Pugwash reference.)
      • Eider oilfield Middle Jurassic operated by Shell
      • Murchison oilfield Straddles the Norwegian median line.
      • Don oilfield
      • Magnus oilfield Big BP rust bucket. Crane is good at dropping logging units.
    • Offshore (West of Shetland) (Serviced from Aberdeen)
      • Clair oilfield A large, but high viscosity field.
      • Schiehallion oilfield
      • Foinaven oilfield


    • Onshore
      • Wietze "near Hanover", discovered in 1859!
      • The Schoenebeek field of the Netherlands extends across the border.
    • No commercial developments offshore


    • Nothing onshore
    • Offshore developments abundant. (There is a strange kink in the German-Danish median line that begs for explanation.) Serviced from Esbjerg, most fields are operated by DONG Energy
      • Nils oilfiled
      • Skjold oilfield
      • Gorm oil and gasfield - Chalk reservoir
      • Roar oilfield - Chalk reservoir
      • Harald oilfield - Chalk reservoir
      • Dan oil and gas field - Chalk reservoir
      • Kraka oilfield - Chalk reservoir
      • Halfdan oil and gas field - Chalk reservoir
      • Tyra oil and gas field - Chalk reservoir
      • Tyra Southeast oil field
      • Svend oil field
      • Valdemar oilfield
      • Lulita gas field
      • Regnar oil field
      • Rolf oil field
      • Dagmar oil field
      • Siri oil field
      • Nini oil field
      • Cecilie oil field
      • South Arne oil and gas field


Reference - Norwegian Petroleum Directorate fact pages on oil fields

    • Onshore developments -none ( Oslo Graben oil seeps??).
    • Offshore developments. Serviced from Bergen, Stavanger, Kristiansund
    • Central North Sea
      • Hod oilfield - Chalk reservoir , Operated by BP
      • Valhall oilfield - Chalk reservoir, operated by BP
      • Eldfisk - Chalk reservoir, operated by ConocoPhillips
      • Ekofisk - Chalk reservoir, operated by ConocoPhillips
      • Embla oilfield - Devonian / Permian Reservoir, operated by ConocoPhillips
      • Tor oilfield - Chalk reservoir, operated by ConocoPhillips
      • Albuskjell oilfield - decommissioned
      • Ula oilfield- Jurassic sandstone reservoir, Operated by BP
      • Gyda oilfield - Jurassic sandstone reservoir, Operated by Talisman Energy
      • Cod oilfield- decommissioned
    • Northern North Sea
      • Sleipner oilfield, Jurassic and Palaeocene reservoirs, operated by Statoil
      • Brisling oilfield
      • Bream oilfield
      • Balder oilfield - Palaeocene/Eocene, operated by ExxonMobil
      • Frigg gas field Large Eocene reservoir gas field,
      • Hild gas field
      • Heimdal gasfield - Palaeocene reservoir, Operated by Norsk Hydro
      • Oseberg oilfield Middle Jurassic sandstone reservoir operated by Norsk Hydro (the only oil rig with a log fire in the accommodation ?? Mad Noggins)
      • Brage oil filed, operated by Norsk Hydro
      • Troll Largest gas field in North Sea operated by Statoil.
      • Gullfaks oil field, Middle Jurassic reservoir operated by Statoil
      • Statfjord along strike from Brent, but structurally deeper, partially in UK sector. Operated by Statoil
      • Snorre oilfield, Middle Jurassic reservoir operated by Statoil
      • Murchison oil field (part of; produced through UK) Operated by CNR resources
      • Agat
    • Haltenbank; numerous developments in production, Heidrun gasfied, Draugen oil field, Ormen Lange etc.

Associated, but not strictly North Sea

  • Ireland (includes Northern Ireland)
    • Onshore
      • Larne; tiny prospect under the basalts.
      • Other small prospects, and significant coal-bed methane.
    • Offshore
      • Kinsale Head; gas development off the coast of Cork
      • Corrib Gas Field; about to start production to a controversial onshore processing plant
      • Inishbeg; prospect announced to the NW of Donegal. Due to be drilled August 2006.
  • Faroes
    • Offshore
      • Various blocks licensed for exploration, several discoveries not yet developed.
  • Iceland
    • Offshore
      • Nothing published, but the idea is not inconceivable on the ridges extending towards Iceland from the Faroes and the East Greenland Coast.
  • East Greenland
    • Onshore
      • No prospects reported, though sediments analogous to the Mesozoic and Caenozoic deposits of the North Sea are known, so there is appreciable interest. Development would be formidably difficult, technically, logistically and politically.
    • Offshore
      • A recent conference on hydrocarbon prospects in arctic Russia (Geological Society, London; February 2006) had several speakers mention major gas prospectivity on the East Greenland coast, but they cited no sources. A conference volume is due towards the end of 2006, which may elaborate.
  • Barents Sea
    • Onshore
      • No significant prospects or potential.
    • Offshore
      • Significant exploration, appraisal and development. Major discoveries the Snøhvit gasfield, operated by Statoil in Norwegian sector and the Stokhmanovskoye gasfield planned to be operated by Gazprom in Russian sector.

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