Oseberg oil field
Oseberg is an offshore oil field
Oil field
An oil field is a region with an abundance of oil wells extracting petroleum from below ground. Because the oil reservoirs typically extend over a large area, possibly several hundred kilometres across, full exploitation entails multiple wells scattered across the area...

 with a gas cap in the North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...

 located 140 km (87 mi) northwest of the city of Bergen
Bergen is the second largest city in Norway with a population of as of , . Bergen is the administrative centre of Hordaland county. Greater Bergen or Bergen Metropolitan Area as defined by Statistics Norway, has a population of as of , ....

 on the southwestern coast of Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

The field, which is 25 km long by 7 km wide, was discovered in 1979 and its development is known to be one of the significant milestones in emergence of Norway's independent oil and gas industry
Petroleum industry
The petroleum industry includes the global processes of exploration, extraction, refining, transporting , and marketing petroleum products. The largest volume products of the industry are fuel oil and gasoline...

. The Oseberg field was named after Oseberg ship
Oseberg ship
The Oseberg ship is a well-preserved Viking ship discovered in a large burial mound at the Oseberg farm near Tønsberg in Vestfold county, Norway.-Burial mound:...

, one of Norway's most significant archeological discoveries. The ancient Viking ship from the early 9th century was discovered in a 1904 historical excavation of a burial mound at the Oseberg Farm, south of Oslo
Oslo is a municipality, as well as the capital and most populous city in Norway. As a municipality , it was established on 1 January 1838. Founded around 1048 by King Harald III of Norway, the city was largely destroyed by fire in 1624. The city was moved under the reign of Denmark–Norway's King...


An extensive subsea pipeline network called Oseberg Transport System
Oseberg Transport System
Oseberg Transport System is a pipeline system in western Norway. It is long and runs from Oseberg, Veslefrikk, Brage, Frøy and Lille-Frigg to Sture terminal, located north of Bergen, Norway. The operation of the pipeline was commenced in 1988...

 (OTS) transports up to 765000 oilbbl/d from the Oseberg area to Sture terminal
Sture terminal
Sture Terminal is an oil terminal at Stura in Øygarden municipality, northwest of Bergen, Norway. It receives oil and condensate from Oseberg, Veslefrikk, Brage, Oseberg Sør, Oseberg Øst, Tune and Huldra fields through Oseberg Transport System and oil from Grane oil field through Grane oil...

 in Norway. The sea depth in the Oseberg area is 100 meters.
The Oseberg Field Centre consists of three platforms
Oil platform
An oil platform, also referred to as an offshore platform or, somewhat incorrectly, oil rig, is a lаrge structure with facilities to drill wells, to extract and process oil and natural gas, and to temporarily store product until it can be brought to shore for refining and marketing...

: Oseberg A, B and D, connected to each other by bridges, in the southern part of the Oseberg field and the Oseberg C platform, which is located 14 kilometers north of the field center. The operator is Statoil
Statoil ASA is a Norwegian petroleum company established in 1972. It merged with Norsk Hydro in 2007 and was known as StatoilHydro until 2009, when the name was changed back to Statoil ASA. The brand Statoil was retained as a chain of fuel stations owned by StatoilHydro...

, in partnership with Petoro
Petoro, a company wholly owned by the state of Norway, manages Norway's portfolio of exploration and production licenses for petroleum and natural gas on the Norwegian continental shelf. This portfolio is collectively called State's Direct Financial Interest . The company also has a control...

, Total
Total S.A.
Total S.A. is a French multinational oil company and one of the six "Supermajor" oil companies in the world.Its businesses cover the entire oil and gas chain, from crude oil and natural gas exploration and production to power generation, transportation, refining, petroleum product marketing, and...

, ExxonMobil
Exxon Mobil Corporation or ExxonMobil, is an American multinational oil and gas corporation. It is a direct descendant of John D. Rockefeller's Standard Oil company, and was formed on November 30, 1999, by the merger of Exxon and Mobil. Its headquarters are in Irving, Texas...

 and ConocoPhillips
ConocoPhillips Company is an American multinational energy corporation with its headquarters located in the Energy Corridor district of Houston, Texas in the United States...

. The field extends into blocks 30/6 and 30/9, parts of Production licenses (PL) 053 and 079.

Exploration history

The first exploration well
Oil well
An oil well is a general term for any boring through the earth's surface that is designed to find and acquire petroleum oil hydrocarbons. Usually some natural gas is produced along with the oil. A well that is designed to produce mainly or only gas may be termed a gas well.-History:The earliest...

 on the PL053 license, 30/6-1, was drilled as a wildcat and spudded on 19 June 1979. The well was plugged and abandoned as a gas discovery on 22 September. Subsequent appraisal wells proved oil in addition to the gas found by the discovery well and Oseberg was produced as an oilfield. The first exploration well on the PL079 license, 30/9-1 was drilled as a wildcat at the end of 1982, but treated as an appraisal after it encountered oil and gas considered to form part of the same accumulation. In 2006, well 30/9-B-19 A proved reserves in the underlying Upper Triassic to Lower Jurassic Statfjord formation. Tests are also being carried out on the overlying Upper Cretaceous Chalk Group reservoir to evaluate the flow characteristics.

The vertical gas column in the Alpha block was 380 m while the underlying oil column was about 215 m before production began.

A total of 31 exploration and appraisal wells have been drilled on the Oseberg structure, although this includes sidetracks and re-entries. Of these wells, only three proved 'dry'.

Development history

Development drilling began in 1985 with a production well drilled from the B template. By the end of 2009 184 development wells had been completed, consisting of a mixture of production wells, observation wells, water injectors
Water injection (oil production)
Water injection refers to the method in oil industry where water is injected back into the reservoir, usually to increase pressure and thereby stimulate production. Water injection wells can be found both on- and offshore, to increase oil recovery from an existing reservoir...

, gas injectors
Gas reinjection
Gas reinjection is the reinjection of natural gas into an underground reservoir, typically one already containing both natural gas and crude oil, in order to increase the pressure within the reservoir and thus induce the flow of crude oil or else sequester gas that cannot be exported...

 and cuttings injectors. Production was from deviated wells until 1992, when the first horizontal well was drilled. By June 1997, 28 horizontal wells had been completed, including three multilaterals. Horizontal drilling close to the oil-water contact
Water contact
Water contact is a term used in the hydrocarbon industry to describe the elevation above which fluids other than water can be found in the pores of a rock....

 was considered key to prolonging the plateau oil production period and achieving high recovery rates.

Seismic data acquisition

The initial discovery well was sited using 2D seismic reflection
Reflection seismology
Reflection seismology is a method of exploration geophysics that uses the principles of seismology to estimate the properties of the Earth's subsurface from reflected seismic waves. The method requires a controlled seismic source of energy, such as dynamite/Tovex, a specialized air gun or a...

 data. In 1982, the first 3D seismic dataset was acquired over Oseberg, to assist with continuing exploration and appraisal drilling. In 1989 and 1991 Statoil acquired two sets of 3D data over the field, using the same parameters, as a feasibility study for a full 4D seismic study. Following the success of the pilot study, additional surveys were shot in 1992, 1999, 2004 and 2007. These surveys are used to actively monitor changes in the gas-oil contact and the water-oil contact as production continues.


Oseberg A is a concrete base platform which includes process equipment and accommodation quarters; Oseberg B sits on top of a steel jacket, and has drilling, production and injection facilities; Oseberg D is a steel platform with gas processing and export equipment which was connected to the Field Centre by a bridge in 1999. Oseberg C is an integrated drilling, accommodation and production platform with a steel jacket.
Oseberg Vestflanke was developed with a subsea template tied back to Oseberg B. Oseberg Delta will be developed with a subsea template tied back to Oseberg D. Production from the Gamma Main structure in the Statfjord Formation started in the spring of 2008 with two wells from the Oseberg Field Center. The facilities at the field center process oil and gas from the fields Oseberg Øst
Oseberg Øst
Oseberg East is an offshore oil field in the North Sea, located east of Oseberg Oil Field. The field was developed with a fixed production, drilling and quarters facility and is operated by Statoil. The first stage phase processing is done at the Oseberg Øst platform...

, Oseberg Sør
Oseberg Sør
Oseberg South is an offshore oil field in the North Sea, located from the coastline and south of Oseberg Oil Field. Oseberg Sør was discovered in 1984. The field was developed with a fixed production, drilling and quarters facility and is operated by Statoil. The first stage phase processing...

 and Tune. The Plan for Development and Operation (PDO) for the northern part of Oseberg was confirmed on 19 January 1988. The PDO for Oseberg D was approved on 13 December 1996, for Oseberg Vestflanke – on 19 December 2003 and for Oseberg Delta on 23 September 2005.
The oil from the field is produced by maintenance of pressure through gas and water injection and by water gas injection (WAG). Injection gas used for pressure maintenance was previously brought from Troll Øst (TOGI) and Oseberg Vest. Other smaller parts of the field produce by pressure depletion.

The field has been producing since 1 December 1988. Plateau oil production of 81,000 Sm3 per day ended in 1997. Current production (total for 2009 to September) as per stats is 3.788063 mill S
Standard conditions for temperature and pressure
Standard condition for temperature and pressure are standard sets of conditions for experimental measurements established to allow comparisons to be made between different sets of data...

Cubic metre
The cubic metre is the SI derived unit of volume. It is the volume of a cube with edges one metre in length. An alternative name, which allowed a different usage with metric prefixes, was the stère...

 of oil, 2.926727 bill Sm3 of gas, 0.462964 mill tonn of NGL
Natural gas processing
Natural-gas processing is a complex industrial process designed to clean raw natural gas by separating impurities and various non-methane hydrocarbons and fluids to produce what is known as pipeline quality dry natural gas.-Background:...

Regional setting

The Oseberg field is one of a series of hydrocarbon accumulations within the Viking Graben
In geology, a graben is a depressed block of land bordered by parallel faults. Graben is German for ditch. Graben is used for both the singular and plural....

. This part of the northern North Sea has been affected by two main rift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....

 episodes; in the Permo
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...

The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

 and the mid-late Jurassic. This leads to complex variations of the earlier syn-rift sequence thickness across the later rift structures. In the Oseberg area, the major faults formed during these two phases dip in opposite directions and the size of the earlier basins are typically double the size of the later. The east-tilted Late Jurassic Oseberg structure is underlain by a larger-scale west-tilted Permo-Triassic half-graben.


The main reservoirs are sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...

s of the Middle Jurassic
Middle Jurassic
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age are called the Dogger....

 Oseberg, Rannoch, Etive, Ness and Tarbert formations of the Brent Group. These are the deposits of prograding
In sedimentary geology and geomorphology, the term progradation refers to the growth of a river delta farther out into the sea over time. This occurs when the mass balance of sediment into the delta is such that the volume of incoming sediment is greater than the volume of the delta that is lost...

River delta
A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...

 systems, with an overall shallowing upwards as the delta filled the available accommodation space. The Oseberg formation represents the deposits of a series of sand-rich deltas that advanced westwards from the Norwegian coastline. The rest of the group are the deposits of the massive northward prograding Brent delta system, which occupied the entire southern part of the Viking graben area. There is a progressive transition in the depositional environment
Sedimentary depositional environment
In geology, sedimentary depositional environment describes the combination of physical, chemical and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be formed after lithification, if the sediment is preserved in the rock...

 from subaqueous fans, through fan deltas and shoreface to delta plain. The uppermost Tarbert formation may represent reworked delta plain deposits at the onset of the marine transgression
Transgression (geology)
A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, resulting in flooding. Transgressions can be caused either by the land sinking or the ocean basins filling with water...

 shown by the overlying claystones of the Viking group. The Brent Group reservoirs, which lie at depths between 2300–2700 m, generally have excellent properties with porosities
Porosity or void fraction is a measure of the void spaces in a material, and is a fraction of the volume of voids over the total volume, between 0–1, or as a percentage between 0–100%...

 around 20–30% and permeabilities ranging up to several darcy
A darcy and millidarcy are units of permeability, named after Henry Darcy. They are not SI units, but they are widely used in petroleum engineering and geology. Like other measures of permeability, a darcy has the same units as area.-Definition:Permeability measures the ability of fluids to...


The Statfjord formation, which is of Ryazanian to Sinemurian
In the geologic timescale, the Sinemurian is an age or stage in the Early or Lower Jurassic epoch or series. It spans the time between 196.5 ± 2 Ma and 189.6 ± 1.5 Ma...

 age is separated from the Brent Group by the Dunlin Group, which is a non-reservoir sequence. This means that there is normally no communication between the Statfjord formation and the Brent Group reservoirs. The Statfjord formation consists of massive sandstones. The lower boundary is taken at the transition from red continental shales of the Lunde formation to the overlying sandstones. The top of the unit, which consists of calcareous sandstones, shows a relatively sharp transition to the dark shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...

s and siltstone
Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.- Description :As its name implies, it is primarily composed of silt sized particles, defined as grains 1/16 - 1/256 mm or 4 to 8 on the Krumbein phi scale...

s of the overlying Dunlin group. The depositional environment changes from alluvial plain and braided stream deposits that make up the bulk of the formation to coarse sandstones with pebble lags and channeling, thought to indicate a coastal environment. The presence of glauconite
Glauconite is an iron potassium phyllosilicate mineral of characteristic green color with very low weathering resistance and very friable.It crystallizes with a monoclinic geometry...

 and marine fossils in the uppermost sandstones indicate deposition in a shallow marine environment.


The trap is a group of three easterly dipping tilted fault blocks associated with westerly dipping normal faults formed by rifting during the Late Jurassic on the east side of the Viking Graben. The three main fault blocks are known as Alpha, Gamma and Alpha North. The eastern boundary of the Oseberg fault blocks with the Horda Platform
Platform (geology)
In geology, a platform is a continental area covered by relatively flat or gently tilted, mainly sedimentary strata, which overlie a basement of consolidated igneous or metamorphic rocks of an earlier deformation...

 is formed by the major Brage fault. The structural dip is an average 6–10 degrees.


The top seal is formed by Upper Jurassic Viking group or Lower Cretaceous Cromer Knoll claystones. There is also evidence in the Oseberg area for some element of fault seal.


The oil in Oseberg is sourced from the Upper Jurassic Draupne formation, equivalent to the Kimmeridge Clay
Kimmeridge Clay
The Kimmeridge Clay Formation is a sedimentary deposit of fossiliferous marine clay which is of Jurassic age. It occurs in Europe.Kimmeridge Clay is arguably the most economically important unit of rocks in the whole of Europe, being the major source rock for oil fields in the North Sea hydrocarbon...

 formation. Oils generated in at least two different 'kitchens' have been identified within the Oseberg area. The gas is likely to be sourced from over-mature Draupne formation in the deepest part of these kitchens.


Initial recoverable reserves for the Oseberg field are estimated as 366.4 million Sm3 oil, 107.0 billion Sm3 gas and 9.3 million tonnes NGL. As of 31 December 2008 remaining recoverable reserves were estimated at 21.1 million Sm3 oil, 85.6 billion Sm3 gas and 3.5 million tonnes NGL.

See also

  • Sture terminal
    Sture terminal
    Sture Terminal is an oil terminal at Stura in Øygarden municipality, northwest of Bergen, Norway. It receives oil and condensate from Oseberg, Veslefrikk, Brage, Oseberg Sør, Oseberg Øst, Tune and Huldra fields through Oseberg Transport System and oil from Grane oil field through Grane oil...

  • Oseberg Transport System
    Oseberg Transport System
    Oseberg Transport System is a pipeline system in western Norway. It is long and runs from Oseberg, Veslefrikk, Brage, Frøy and Lille-Frigg to Sture terminal, located north of Bergen, Norway. The operation of the pipeline was commenced in 1988...

  • Grane oil field
    Grane oil field
    Grane is an offshore oil field in the North Sea located west of the city of Haugesund on the western coast of Norway. It is Norway's first heavy crude oil production field and Statoil's largest heavy oil field. The oil from the field, located in Block 25/11 is transported to Sture terminal via...

  • Grane oil pipeline
    Grane Oil Pipeline
    Grane oil pipeline is a pipeline system in western Norway. It is long and runs from Grane oil field to Sture terminal, located north of Bergen, Norway. The pipeline operations commenced with start of production in the Grane oil field.-Technical features:...

  • North Sea oil
    North Sea oil
    North Sea oil is a mixture of hydrocarbons, comprising liquid oil and natural gas, produced from oil reservoirs beneath the North Sea.In the oil industry, the term "North Sea" often includes areas such as the Norwegian Sea and the area known as "West of Shetland", "the Atlantic Frontier" or "the...

  • Economy of Norway
    Economy of Norway
    The economy of Norway is a developed mixed economy with heavy state-ownership in strategic areas of the economy. Although sensitive to global business cycles, the economy of Norway has shown robust growth since the start of the industrial era...

  • Ekofisk oil field
    Ekofisk oil field
    Ekofisk is an oil field in the Norwegian sector of the North Sea about southwest of Stavanger. Discovered in 1969, it remains one of the most important oil fields in the North Sea. Production began in 1971 after the construction of a series of off-shore platforms by Phillips Petroleum Company...

External links

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