Ekofisk oil field
Encyclopedia
Ekofisk is an oil field in the Norwegian
sector of the North Sea
about 200 miles (321.9 km) 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. Oil production is planned to continue until at least 2050.
Ekofisk reservoir consists of Cod, Ekofisk, West Ekofisk, Tor, Albuskjell, Eldfisk, Edda and Embla oil fields. The Ekofisk Center is a vast complex of platforms and structures creating a transportation hub also for surrounding fields such as Valhall
, Hod, Gyda
, Ula
, Statfjord
, Heimdal
, Tommeliten and Gullfaks
. The whole complex consists of 29 platforms. Produced oil is transported by the Norpipe
oil pipeline to the ConocoPhillips Teesside
Terminal in the United Kingdom. Natural gas is transported by the Norpipe
gas pipeline to Emden
in Germany.
. Detailed geological investigation showed that it was the result of delayed compactional diagenesis
of the Chalk Formation
reservoir rocks. As hydrocarbons were produced and replaced with water, the Chalk began to re-dissolve due to high-pressure inter-grain contacts and redeposit in a more compact, lower porosity configuration. Movements of several metres were recorded, and it was calculated that the total subsidence
would almost be 6 metres (19.7 ft) at the end of the concession of Phillips Petroleum, too much to keep the platforms secure. The Norwegian government pressed Phillips to take action and the French company TECHNIP was ordered to find a solution. As 5 of 7 platforms were interconnected, they had to be jacked-up by about 6 metres (19.7 ft) at the same time. The solution was that the steel tubular legs of the platforms would be extended. Subsequently large flanges were welded to these legs and when all flanges were welded and the legs cut, five platforms would be lifted simultaneously in one operation then extension pipes would be mounted in between the flanges. After bolting all flanges the platforms would be safe again.
The four days lifting was completed on August 17, 1987 at 11:30 pm thanks to 108 hydraulic cylinders synchronised with a network of 14 NUM 760FCNCs. The position tolerance of the cylinders with each other (+/- 3 millimetre (0.118110236220472 in) for a 6 metres (19.7 ft) extension per platform and +/- 100 millimetres (3.9 in) between platforms) was to be kept for 38 hours. During the welding of the flanges to the legs, these hydraulic cylinders took over the entire load. A couple of days before this great jack-up, the hotel platform was lifted, as it was not interconnected with the others. The total lifting capacity of all these cylinders was approximately 40000 tonnes (39,368.1 LT) and was published in the Guinness book of records as being the largest jack-up ever.
occurred at the Ekofisk Bravo platform, due to an incorrectly installed downhole safety valve. At an estimated 80000–126000 bbl (12,718,983.6–20,032,399.2 ) total, this is the largest blowout in the North Sea. Red Adair
and his crew assisted with capping the blowout.
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...
sector of 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...
about 200 miles (321.9 km) southwest of Stavanger
Stavanger
Stavanger is a city and municipality in the county of Rogaland, Norway.Stavanger municipality has a population of 126,469. There are 197,852 people living in the Stavanger conurbation, making Stavanger the fourth largest city, but the third largest urban area, in Norway...
. 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. Oil production is planned to continue until at least 2050.
Ekofisk reservoir consists of Cod, Ekofisk, West Ekofisk, Tor, Albuskjell, Eldfisk, Edda and Embla oil fields. The Ekofisk Center is a vast complex of platforms and structures creating a transportation hub also for surrounding fields such as Valhall
Valhall oil field
Valhall is an oil field in the Norwegian sector of the North Sea. Discovered in 1975, production began in 1982 and is expected to continue until 2050. Valhall is located in 70 metres of water.- Development :...
, Hod, Gyda
Gyda Oil Field
Gyda is an offshore oil field located in the southern Norwegian section of North Sea along with Ula, Tambar and Tambar East fields making up the UGT area, usually attributed to DONG Energy's main areas of exploration and production activity. The Gyda field was discovered in 1980 and started...
, Ula
Ula oil field
Ula is an offshore oil field located in the southern Norwegian section of North Sea along with Gyda, Tambar and Tambar East fields making up the UGT area, usually attributed to DONG Energy's main areas of exploration and production activity. The Ula field was discovered in 1976 and came online in...
, Statfjord
Statfjord oil field
The Statfjord oil field is an enormous oil and gas field in the Norwegian sector of the North Sea operated by Statoil.It is a trans-median field crossing the Norwegian and UK North Sea Boundary with approximately 15% being in the UK Continental Shelf waters. At peak production it produced over of...
, Heimdal
Heimdal gas field
Heimdal is an offshore natural gas field in the North Sea located northwest of the Stavanger, Norway. Heimdal serves as a connection hub for processing and distribution of natural gas from satellite fields....
, Tommeliten and Gullfaks
Gullfaks oil field
Gullfaks is an oil and gas field in the Norwegian sector of the North Sea operated by Statoil. It was discovered in 1979, in block 34/10, at a water depth of 135 meters. The initial recoverable reserve is , and the remaining recoverable reserve in 2004 is . This oil field reached peak production in...
. The whole complex consists of 29 platforms. Produced oil is transported by the Norpipe
Norpipe
Norpipe is the undersea oil and natural gas pipeline's system in the North Sea. It supplies oil from the Norwegian Ekofisk and associated fields in the North Sea to the United Kingdom and natural gas to Germany.-Oil pipeline:...
oil pipeline to the ConocoPhillips Teesside
Teesside
Teesside is the name given to the conurbation in the north east of England made up of the towns of Middlesbrough, Stockton-on-Tees, Redcar, Billingham and surrounding settlements near the River Tees. It was also the name of a local government district between 1968 and 1974—the County Borough of...
Terminal in the United Kingdom. Natural gas is transported by the Norpipe
Norpipe
Norpipe is the undersea oil and natural gas pipeline's system in the North Sea. It supplies oil from the Norwegian Ekofisk and associated fields in the North Sea to the United Kingdom and natural gas to Germany.-Oil pipeline:...
gas pipeline to Emden
Emden
Emden is a city and seaport in the northwest of Germany, on the river Ems. It is the main city of the region of East Frisia; in 2006, the city had a total population of 51,692.-History:...
in Germany.
Subsidence
In the mid-1980s the Ekofisk field as a whole and the platforms in particular were found to be suffering from an unexpected degree of subsidenceSubsidence
Subsidence is the motion of a surface as it shifts downward relative to a datum such as sea-level. The opposite of subsidence is uplift, which results in an increase in elevation...
. Detailed geological investigation showed that it was the result of delayed compactional diagenesis
Diagenesis
In geology and oceanography, diagenesis is any chemical, physical, or biological change undergone by a sediment after its initial deposition and during and after its lithification, exclusive of surface alteration and metamorphism. These changes happen at relatively low temperatures and pressures...
of the Chalk Formation
Chalk Formation
The Chalk Group is a lithostratigraphic unit in the northwestern part of Europe. It is characterised by thick deposits of chalk, a soft porous white limestone, deposited in a marine environment during the Upper Cretaceous period.Chalk is a limestone that consists of coccolith biomicrite...
reservoir rocks. As hydrocarbons were produced and replaced with water, the Chalk began to re-dissolve due to high-pressure inter-grain contacts and redeposit in a more compact, lower porosity configuration. Movements of several metres were recorded, and it was calculated that the total subsidence
Subsidence
Subsidence is the motion of a surface as it shifts downward relative to a datum such as sea-level. The opposite of subsidence is uplift, which results in an increase in elevation...
would almost be 6 metres (19.7 ft) at the end of the concession of Phillips Petroleum, too much to keep the platforms secure. The Norwegian government pressed Phillips to take action and the French company TECHNIP was ordered to find a solution. As 5 of 7 platforms were interconnected, they had to be jacked-up by about 6 metres (19.7 ft) at the same time. The solution was that the steel tubular legs of the platforms would be extended. Subsequently large flanges were welded to these legs and when all flanges were welded and the legs cut, five platforms would be lifted simultaneously in one operation then extension pipes would be mounted in between the flanges. After bolting all flanges the platforms would be safe again.
The four days lifting was completed on August 17, 1987 at 11:30 pm thanks to 108 hydraulic cylinders synchronised with a network of 14 NUM 760FCNCs. The position tolerance of the cylinders with each other (+/- 3 millimetre (0.118110236220472 in) for a 6 metres (19.7 ft) extension per platform and +/- 100 millimetres (3.9 in) between platforms) was to be kept for 38 hours. During the welding of the flanges to the legs, these hydraulic cylinders took over the entire load. A couple of days before this great jack-up, the hotel platform was lifted, as it was not interconnected with the others. The total lifting capacity of all these cylinders was approximately 40000 tonnes (39,368.1 LT) and was published in the Guinness book of records as being the largest jack-up ever.
Bravo Blowout
In April 1977, an oil well blowoutBlowout (well drilling)
A blowout is the uncontrolled release of crude oil and/or natural gas from an oil well or gas well after pressure control systems have failed....
occurred at the Ekofisk Bravo platform, due to an incorrectly installed downhole safety valve. At an estimated 80000–126000 bbl (12,718,983.6–20,032,399.2 ) total, this is the largest blowout in the North Sea. Red Adair
Red Adair
Paul Neal "Red" Adair was an American oil well firefighter. He became world notable as an innovator in the highly specialized and extremely hazardous profession of extinguishing and capping blazing, erupting oil well blowouts, both land-based and offshore.-Life and career:Adair was born in...
and his crew assisted with capping the blowout.