Offshore concrete structure
Encyclopedia
Offshore concrete structures have been in use successfully for about 30 years. They serve the same purpose as their steel counterparts in the oil and gas production and storage. The first concrete oil platform
has been installed in the North Sea in the Ekofisk field in 1973 by Phillips Petroleum
. Since then 47 major concrete offshore structures have been built, whereby 21 of the 47 concrete substructures have been designed (concept and detail designs ) by Dr. techn. Olav Olsen.
Depending on the circumstances, platforms may be attached to the ocean floor, consist of an artificial island, or be floating. Generally, offshore concrete structures are classified into fixed and floating structures. Fixed structures are mostly built as concrete gravity based structures (CGS, also termed as caisson type), where the loads bear down directly on the uppermost layers as soil pressure. The caisson provides buoyancy during construction and towing and acts also as a foundation structure in the operation phase. Furthermore, the caisson could be used as storage volume for oil or other liquids.
Floating units will be held in position by anchored wires or chains in a spread mooring pattern. Because of the low stiffness in those systems, the natural frequency is low and the structure can move in all six degrees of freedom. Floating units serve as productions units, storage and offloading units (FSO) or for crude oil or as terminals for liquefied natural gas (LNG). A more recent development is concrete sub-sea structures.
Concrete offshore structures show an excellent performance. They are highly durable, constructed of almost maintenance-free material, suitable for harsh and/or arctic environment (like ice and seismic regions), can carry heavy topsides, often offer storage capacities, are suitable for soft grounds ad are very economical for water depths larger than 150m. Most gravity-type platforms need no additional fixing because of their large foundation dimensions and extremely high weight.
Concrete offshore platforms of the gravity-base type are almost always constructed in their vertical attitude. This allows the inshore installation of deck girders and equipment and the later transport of the whole structure to the installation site.
The most common concrete designs are:
refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors
in Norway. A Condeep
usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise. The original Condeep always rests on the sea floor, and the shafts rise to about 30m above the sea level. The platform deck itself is not a part of the construction.
The Condeep
Platforms Brent B (1975) and Brent D (1976) were designed for a water depth of 142m in the Brent oilfield
operated by Shell
. Their main mass is represented by the storage tank (ca. 100m diameter and 56m high, consisting of 19 cylindrical compartments with 20m diameter). Three of the cells are extended into shafts tapering off at the surface and carrying a steel deck. The tanks serve as storage of crude oil in the operation phase. During the installation these tanks have been used as ballast compartment.
Among the largest Condeep
type platform are the Troll A platform
and the Gullfaks C. Troll A
was built within four years and deployed in 1995 to produce gas from the Troll oil field
which is operated by Norske Shell.
A detailed overview about Condeep
platforms is given in a separate article.
Concrete Gravity Base Structures (CGBS) is a further development of the first-generation Condeep
drilling/production platforms installed in the North Sea between the late 1970s and mid '90s. The CGBS have no oil storage facilities and the topside installations will be carried out in the field by a float-over mating method. Current or most recent projects are:
The structure has a shape not unlike a marine sea island and is surrounded by a perforated breakwater wall (Jarlan patent).
The original proposal of the French group C G DORIS (Compagnie General pour les Developments Operationelles des Richesses Sous-Marines) for a prestressed post-tensioned concrete "island" structure was adopted on cost and operational grounds. DORIS was general contractor responsible for the structural design: the concrete design was prepared and supervised on behalf of DORIS by Europe-Etudes. Further example for the C G DORIS designs are the Frigg platforms, the Ninian Platform and the Schwedeneck platforms.
Thedesign typically consists of a large volume caisson based on the sea floor merging into a monolithic structure , which is offering the base for the deck. The single main leg is surrounded by an outer breaker wall perforated with so called Jarlan holes. This wall is intended to break up waves, thus reducing their forces.
divided up the construction of four offshore platforms. Redpath Dorman Long at Methil in Fife, Scotland getting Brent A, the two concrete Condeeps B and D were to be built in Norway by Norwegian Contractors (NC) of Stavanger, and C (also concrete) was to be built by McAlpine at Ardyne Point on the Clyde (which is known as the ANDOC design). The ANDOC design can be considered as the British construction industry's attempt to compete with Norway in this sector. McAlpine constructed three concrete platforms for the North Sea oil industry at Ardyne Point. The ANDOC type is very similar to the Sea Tank design, but the four concrete legs terminate and steel legs take over to support the deck.
dry-build Concrete Gravity Substructure (CGS) concept was originally developed by Arup
in 1989 for Hamilton Brothers' Ravenspurn North. The Arup
CGS are designed to be simple to install, and are fully removable. Simplicity and repetition of concrete structural elements, low reinforcement and pre-stress densities as well as the use of normal density concrete lead to economical construction costs. Typical for the Arup
CGS is the inclined installation technique. This technique helps to maximise economy and provide a robust offshore emplacement methodology. Further projects have been the Malampaya project in the Philippines and the Wandoo Full Field Development on the North West Shelf of Western Australia.
platforms float during construction and tow-out but will finally be placed on the ground. Permanently floating concrete structures are used in the discovery of oil and gas deposits, for oil and gas production, as storage and offloading units and also for heavy lifting systems.
Common designs for floating concrete structures are the barge or ship design, the platform design (semi-submersible, TLP) as well as the floating terminals e.g. for LNG.
Floating production, storage, and offloading systems (FPSOS) receive crude oil from deep-water wells and store it in their hull tanks until the crude is transferred into tank ships or transport barges. In addition to FPSO’s, there have been a number of ship-shaped Floating Storage and Offloading (FSO) systems (vessels with no production processing equipment) used in these same areas to support oil and gas developments. An FSO is typically used as a storage unit in remote locations far from pipelines or other infrastructures.
The first barge of prestressed concrete has been designed in the early 1970s as an LPG (liquefied petroleum gas) storage barge in the Ardjuna Field (Indonesia). This barge is built of reinforced and prestressed concrete containing cylindrical tanks each having a cross-section perpendicular to its longitudinal axes that comprises a preferably circular curved portion corresponding to the bottom.
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...
has been installed in the North Sea in the Ekofisk field in 1973 by Phillips Petroleum
Phillips Petroleum
Phillips Petroleum Company was founded in 1917 by L.E. Phillips and Frank Phillips, of Bartlesville, Oklahoma. Their younger brother Waite Phillips was the benefactor of Philmont Scout Ranch....
. Since then 47 major concrete offshore structures have been built, whereby 21 of the 47 concrete substructures have been designed (concept and detail designs ) by Dr. techn. Olav Olsen.
Introduction
Concrete offshore structures are mostly used in the petroleum industry as drilling, extraction or storage units for crude oil or natural gas. Those large structures house machinery and equipment needed to drill and/or extract oil and gas. But concrete structures are not only limited to applications within the oil and gas industry. Several conceptual studies have shown recently, that concrete support structures for offshore wind turbines are very competitive compared to common steel structures, especially for larger water depths.Depending on the circumstances, platforms may be attached to the ocean floor, consist of an artificial island, or be floating. Generally, offshore concrete structures are classified into fixed and floating structures. Fixed structures are mostly built as concrete gravity based structures (CGS, also termed as caisson type), where the loads bear down directly on the uppermost layers as soil pressure. The caisson provides buoyancy during construction and towing and acts also as a foundation structure in the operation phase. Furthermore, the caisson could be used as storage volume for oil or other liquids.
Floating units will be held in position by anchored wires or chains in a spread mooring pattern. Because of the low stiffness in those systems, the natural frequency is low and the structure can move in all six degrees of freedom. Floating units serve as productions units, storage and offloading units (FSO) or for crude oil or as terminals for liquefied natural gas (LNG). A more recent development is concrete sub-sea structures.
Concrete offshore structures show an excellent performance. They are highly durable, constructed of almost maintenance-free material, suitable for harsh and/or arctic environment (like ice and seismic regions), can carry heavy topsides, often offer storage capacities, are suitable for soft grounds ad are very economical for water depths larger than 150m. Most gravity-type platforms need no additional fixing because of their large foundation dimensions and extremely high weight.
Fixed structures
Since the 1970s, several fixed concrete platform designs have been developed. Most of the designs have in common a base caisson (normally for storage of oil) and shafts penetrating the water surface to carry the topside. In the shafts normally utility systems for offloading, drilling, draw down and ballast are put up.Concrete offshore platforms of the gravity-base type are almost always constructed in their vertical attitude. This allows the inshore installation of deck girders and equipment and the later transport of the whole structure to the installation site.
The most common concrete designs are:
- Condeep (with one, two, three or four columns)
- ANDOC (with four columns)
- Sea Tank (with two or four columns)
- C G Doris
- ArupArupArup is a global professional services firm headquartered in London, United Kingdom which provides engineering, design, planning, project management and consulting services for all aspects of the built environment. The firm is present in Africa, the Americas, Australasia, East Asia, Europe and the...
Concrete Gravity Substructure (CGS)
Condeep Type
CondeepCondeep
Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise...
refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors
Norwegian Contractors
Norwegian Contractors AS was the world leading turnkey concrete gravity base structure supplierin the period of 1974 to 1994. Aker Marine Contractors AS was established in 1995 and is a continuance of the marine activities in Norwegian Contractors AS.Norwegian Contractors AS have worked on...
in Norway. A Condeep
Condeep
Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise...
usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise. The original Condeep always rests on the sea floor, and the shafts rise to about 30m above the sea level. The platform deck itself is not a part of the construction.
The Condeep
Condeep
Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise...
Platforms Brent B (1975) and Brent D (1976) were designed for a water depth of 142m in the Brent oilfield
Brent oilfield
The Brent field is an oil field located in the East Shetland Basin north-east of Lerwick, Shetland Islands, Scotland at the water depth of . The field operated by Shell UK Limited was once one of the most productive parts of the UK's offshore assets but is now nearing the end of its useful...
operated by Shell
Royal Dutch Shell
Royal Dutch Shell plc , commonly known as Shell, is a global oil and gas company headquartered in The Hague, Netherlands and with its registered office in London, United Kingdom. It is the fifth-largest company in the world according to a composite measure by Forbes magazine and one of the six...
. Their main mass is represented by the storage tank (ca. 100m diameter and 56m high, consisting of 19 cylindrical compartments with 20m diameter). Three of the cells are extended into shafts tapering off at the surface and carrying a steel deck. The tanks serve as storage of crude oil in the operation phase. During the installation these tanks have been used as ballast compartment.
Among the largest Condeep
Condeep
Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise...
type platform are the Troll A platform
Troll A platform
The Troll A platform is a condeep offshore natural gas platform in the Troll gas field off the west coast of Norway. It is the tallest construction that has ever been moved to another position, relative to the surface of the Earth, and is among the largest and most complex engineering projects in...
and the Gullfaks C. Troll A
Troll A platform
The Troll A platform is a condeep offshore natural gas platform in the Troll gas field off the west coast of Norway. It is the tallest construction that has ever been moved to another position, relative to the surface of the Earth, and is among the largest and most complex engineering projects in...
was built within four years and deployed in 1995 to produce gas from the Troll oil field
Troll oil field
Troll is a natural gas and oil field in the Norwegian sector of the North Sea, North-West of Bergen, west of the island of Fedje.Although Troll is primarily a gas field – one of the biggest in the North Sea, holding 60% of Norway’s gas reserves – it also possesses significant quantities of oil,...
which is operated by Norske Shell.
A detailed overview about Condeep
Condeep
Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise...
platforms is given in a separate article.
Concrete Gravity Base Structures (CGBS) is a further development of the first-generation Condeep
Condeep
Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise...
drilling/production platforms installed in the North Sea between the late 1970s and mid '90s. The CGBS have no oil storage facilities and the topside installations will be carried out in the field by a float-over mating method. Current or most recent projects are:
- Sakhalin-IISakhalin-IIThe Sakhalin-2 project is an oil and gas development in Sakhalin Island, Russia. It includes development of the Piltun-Astokhskoye oil field and the Lunskoye natural gas field offshore Sakhalin Island in the Okhotsk Sea, and associated infrastructure onshore. The project is managed and operated...
platforms (Molikpaq (Piltun-Astokhskoye A; PA-A) platform, Piltun-Astokhskoye B (PA-B) platform and Lunskoye (LUN-A) platform) - Malampaya
- Wandoo
C G DORIS Type
The first concrete gravity platform in the North Sea was a C G Doris platform, the Ekofisk Tank, in Norwegian waters.The structure has a shape not unlike a marine sea island and is surrounded by a perforated breakwater wall (Jarlan patent).
The original proposal of the French group C G DORIS (Compagnie General pour les Developments Operationelles des Richesses Sous-Marines) for a prestressed post-tensioned concrete "island" structure was adopted on cost and operational grounds. DORIS was general contractor responsible for the structural design: the concrete design was prepared and supervised on behalf of DORIS by Europe-Etudes. Further example for the C G DORIS designs are the Frigg platforms, the Ninian Platform and the Schwedeneck platforms.
Thedesign typically consists of a large volume caisson based on the sea floor merging into a monolithic structure , which is offering the base for the deck. The single main leg is surrounded by an outer breaker wall perforated with so called Jarlan holes. This wall is intended to break up waves, thus reducing their forces.
ANDOC Type
To achieve its goal and extract oil within five years after discovering the Brent reservoir ShellRoyal Dutch Shell
Royal Dutch Shell plc , commonly known as Shell, is a global oil and gas company headquartered in The Hague, Netherlands and with its registered office in London, United Kingdom. It is the fifth-largest company in the world according to a composite measure by Forbes magazine and one of the six...
divided up the construction of four offshore platforms. Redpath Dorman Long at Methil in Fife, Scotland getting Brent A, the two concrete Condeeps B and D were to be built in Norway by Norwegian Contractors (NC) of Stavanger, and C (also concrete) was to be built by McAlpine at Ardyne Point on the Clyde (which is known as the ANDOC design). The ANDOC design can be considered as the British construction industry's attempt to compete with Norway in this sector. McAlpine constructed three concrete platforms for the North Sea oil industry at Ardyne Point. The ANDOC type is very similar to the Sea Tank design, but the four concrete legs terminate and steel legs take over to support the deck.
Arup Concrete Gravity Substructure (CGS)
The ArupArup
Arup is a global professional services firm headquartered in London, United Kingdom which provides engineering, design, planning, project management and consulting services for all aspects of the built environment. The firm is present in Africa, the Americas, Australasia, East Asia, Europe and the...
dry-build Concrete Gravity Substructure (CGS) concept was originally developed by Arup
Arup
Arup is a global professional services firm headquartered in London, United Kingdom which provides engineering, design, planning, project management and consulting services for all aspects of the built environment. The firm is present in Africa, the Americas, Australasia, East Asia, Europe and the...
in 1989 for Hamilton Brothers' Ravenspurn North. The Arup
Arup
Arup is a global professional services firm headquartered in London, United Kingdom which provides engineering, design, planning, project management and consulting services for all aspects of the built environment. The firm is present in Africa, the Americas, Australasia, East Asia, Europe and the...
CGS are designed to be simple to install, and are fully removable. Simplicity and repetition of concrete structural elements, low reinforcement and pre-stress densities as well as the use of normal density concrete lead to economical construction costs. Typical for the Arup
Arup
Arup is a global professional services firm headquartered in London, United Kingdom which provides engineering, design, planning, project management and consulting services for all aspects of the built environment. The firm is present in Africa, the Americas, Australasia, East Asia, Europe and the...
CGS is the inclined installation technique. This technique helps to maximise economy and provide a robust offshore emplacement methodology. Further projects have been the Malampaya project in the Philippines and the Wandoo Full Field Development on the North West Shelf of Western Australia.
Floating structures
Since concrete is quite resistant against salt water and keep maintenance costs low, floating concrete structures have become rather attractive to the oil and gas industry within the last two decades. Temporarily floating structures like e.g. the CondeepCondeep
Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise...
platforms float during construction and tow-out but will finally be placed on the ground. Permanently floating concrete structures are used in the discovery of oil and gas deposits, for oil and gas production, as storage and offloading units and also for heavy lifting systems.
Common designs for floating concrete structures are the barge or ship design, the platform design (semi-submersible, TLP) as well as the floating terminals e.g. for LNG.
Floating production, storage, and offloading systems (FPSOS) receive crude oil from deep-water wells and store it in their hull tanks until the crude is transferred into tank ships or transport barges. In addition to FPSO’s, there have been a number of ship-shaped Floating Storage and Offloading (FSO) systems (vessels with no production processing equipment) used in these same areas to support oil and gas developments. An FSO is typically used as a storage unit in remote locations far from pipelines or other infrastructures.
Semi-Submersible
Semi-submersible marine structures are typically only movable by towing. Semi-submersible platforms have the principal characteristic of remaining in a substantially stable position, presenting small movements when they experience environmental forces such as the wind, waves and currents. Semi-Submersible platforms have pontoons and columns, typically two parallel spaced apart pontoons with buoyant columns upstanding from those pontoons to support a deck. Some of the semi-submersible vessels only have a single caisson, or column, usually denoted as a buoy while others utilize three or more columns extended upwardly from buoyant pontoons. For activities which require a stable offshore platform, the vessel is then ballasted down so that the pontoons are submerged, and only the buoyant columns pierce the water surface - thus giving the vessel a substantial buoyancy with a small water-plane area. The only concrete semi-submersible in existence is Troll B.Tension Leg Platform (TLP)
A TLP is a buoyant platform, which is held in place by a mooring system. TLP mooring is different to conventional chained or wire mooring systems. The platform is held in place with large steel tendons fastened to the sea floor. Those tendons are held in tension by the buoyancy of the hull. Statoil's Heidrun TLP is the only one with a concrete hull, all other TLPs have steel hulls.Barge/Ship Design
FPSO or FSO systems are typically barge/ship-shaped and store crude oil in tanks located in the hull of the vessel. Their turret structures are designed to anchor the vessel, allow “weather vaning” of the units to accommodate environmental conditions, permit the constant flow of oil and production fluids from vessel to undersea field, all while being a structure capable of quick disconnect in the event of emergency.The first barge of prestressed concrete has been designed in the early 1970s as an LPG (liquefied petroleum gas) storage barge in the Ardjuna Field (Indonesia). This barge is built of reinforced and prestressed concrete containing cylindrical tanks each having a cross-section perpendicular to its longitudinal axes that comprises a preferably circular curved portion corresponding to the bottom.
Major offshore concrete structures
Following table summarizes the major eziating offshore concrete structures.| No. | Year Installed | Operator | Field/Unit | Structure Type | Depth | Location | Design by |
|---|---|---|---|---|---|---|---|
| 1 | 1973 | Phillips Phillips Petroleum Phillips Petroleum Company was founded in 1917 by L.E. Phillips and Frank Phillips, of Bartlesville, Oklahoma. Their younger brother Waite Phillips was the benefactor of Philmont Scout Ranch.... |
Ekofisk | Tank - DORIS | 71 m | North Sea (N) | DORIS |
| 2 | 1974 | Atlantic Richfield | Ardjuna Field | LPG Barge | 43 m | Indonesia | Berger/ABAM |
| 3 | 1975 | Mobil Mobil Mobil, previously known as the Socony-Vacuum Oil Company, was a major American oil company which merged with Exxon in 1999 to form ExxonMobil. Today Mobil continues as a major brand name within the combined company, as well as still being a gas station sometimes paired with their own store or On... |
Beryl A | Condeep Condeep Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise... 3 shafts |
118 m | North Sea (UK) | NC/Olav Olsen |
| 4 | 1975 | Shell Royal Dutch Shell Royal Dutch Shell plc , commonly known as Shell, is a global oil and gas company headquartered in The Hague, Netherlands and with its registered office in London, United Kingdom. It is the fifth-largest company in the world according to a composite measure by Forbes magazine and one of the six... |
Brent B | Condeep Condeep Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise... 3 shafts |
140 m | North Sea (UK) | NC/Olav Olsen |
| 5 | 1975 | Elf Elf Aquitaine Elf Aquitaine was a French oil company which merged with TotalFina to form TotalFinaElf. The new company changed its name to Total in 2003... |
Frigg CDP1 | CGS 1 shaft, Jarlan Wall | 104 m | North Sea (UK) | DORIS |
| 6 | 1976 | Shell Royal Dutch Shell Royal Dutch Shell plc , commonly known as Shell, is a global oil and gas company headquartered in The Hague, Netherlands and with its registered office in London, United Kingdom. It is the fifth-largest company in the world according to a composite measure by Forbes magazine and one of the six... |
Brent D | Condeep Condeep Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise... 3 shafts |
140 m | North Sea (UK) | NC/Olav Olsen |
| 7 | 1976 | Elf Elf Aquitaine Elf Aquitaine was a French oil company which merged with TotalFina to form TotalFinaElf. The new company changed its name to Total in 2003... |
Frigg TP1 | CGS 2 shafts | 104 m | North Sea (UK) | Sea Tank |
| 8 | 1976 | Elf Elf Aquitaine Elf Aquitaine was a French oil company which merged with TotalFina to form TotalFinaElf. The new company changed its name to Total in 2003... |
Frigg MCP-01 | CGS 1 shaft, Jarlan Wall | 94 m | North Sea (N) | DORIS |
| 9 | 1977 | Shell Royal Dutch Shell Royal Dutch Shell plc , commonly known as Shell, is a global oil and gas company headquartered in The Hague, Netherlands and with its registered office in London, United Kingdom. It is the fifth-largest company in the world according to a composite measure by Forbes magazine and one of the six... |
Dunlin A | CGS 4 shafts | 153 m | North Sea (UK) | ANDOC |
| 10 | 1977 | Elf Elf Aquitaine Elf Aquitaine was a French oil company which merged with TotalFina to form TotalFinaElf. The new company changed its name to Total in 2003... |
Frigg TCP2 | Condeep Condeep Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise... 3 shafts |
104 m | North Sea (N) | NC/Olav Olsen |
| 11 | 1977 | Mobil Mobil Mobil, previously known as the Socony-Vacuum Oil Company, was a major American oil company which merged with Exxon in 1999 to form ExxonMobil. Today Mobil continues as a major brand name within the combined company, as well as still being a gas station sometimes paired with their own store or On... |
Statfjord A | Condeep Condeep Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise... 3 shafts |
145 m | North Sea (N) | NC/Olav Olsen |
| 12 | 1977 | Petrobras Petrobras Petróleo Brasileiro or Petrobras is a semi-public Brazilian multinational energy corporation headquartered in Rio de Janeiro, Brazil. It is the largest company in Latin America by market capitalization and revenue, and the largest company headquartered in the Southern Hemisphere by market... |
Ubarana-Pub 3 | CGS caisson | 15 m | Brazil | ? |
| 13 | 1978 | Petrobras Petrobras Petróleo Brasileiro or Petrobras is a semi-public Brazilian multinational energy corporation headquartered in Rio de Janeiro, Brazil. It is the largest company in Latin America by market capitalization and revenue, and the largest company headquartered in the Southern Hemisphere by market... |
Ubarana-Pub 2 | CGS caisson | 15 m | Brazil | ? |
| 14 | 1978 | Petrobras Petrobras Petróleo Brasileiro or Petrobras is a semi-public Brazilian multinational energy corporation headquartered in Rio de Janeiro, Brazil. It is the largest company in Latin America by market capitalization and revenue, and the largest company headquartered in the Southern Hemisphere by market... |
Ubarana-Pag 2 | CGS caisson | 15 m | Brazil | ? |
| 15 | 1978 | Shell Royal Dutch Shell Royal Dutch Shell plc , commonly known as Shell, is a global oil and gas company headquartered in The Hague, Netherlands and with its registered office in London, United Kingdom. It is the fifth-largest company in the world according to a composite measure by Forbes magazine and one of the six... |
Cormorant A | CGS 4 shafts | 149 m | North Sea (UK) | Sea Tank |
| 16 | 1978 | Chevron Chevron Corporation Chevron Corporation is an American multinational energy corporation headquartered in San Ramon, California, United States and active in more than 180 countries. It is engaged in every aspect of the oil, gas, and geothermal energy industries, including exploration and production; refining,... |
Ninian Central | CGS 1 shaft, Jarlan Wall | 136 m | North Sea (UK) | DORIS |
| 17 | 1978 | Shell Royal Dutch Shell Royal Dutch Shell plc , commonly known as Shell, is a global oil and gas company headquartered in The Hague, Netherlands and with its registered office in London, United Kingdom. It is the fifth-largest company in the world according to a composite measure by Forbes magazine and one of the six... |
Brent C | CGS 4 shafts | 141 m | North Sea (UK) | Sea Tank |
| 18 | 1981 | Mobil Mobil Mobil, previously known as the Socony-Vacuum Oil Company, was a major American oil company which merged with Exxon in 1999 to form ExxonMobil. Today Mobil continues as a major brand name within the combined company, as well as still being a gas station sometimes paired with their own store or On... |
Statfjord B | Condeep Condeep Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise... 4 shafts |
145 m | North Sea (N) | NC/olav Olsen |
| 19 | 1981 | Amoco Canada Amoco Amoco Corporation, originally Standard Oil Company , was a global chemical and oil company, founded in 1889 around a refinery located in Whiting, Indiana, United States.... |
Tarsiut Island | 4 hollow caissons | 16 m | Beaufort Sea | ? |
| 20 | 1982 | Phillips Phillips Petroleum Phillips Petroleum Company was founded in 1917 by L.E. Phillips and Frank Phillips, of Bartlesville, Oklahoma. Their younger brother Waite Phillips was the benefactor of Philmont Scout Ranch.... |
Maureen ALC | Concrete base artic. LC | 92 m | North Sea (UK) | ? |
| 21 | 1983 | Texaco Texaco Texaco is the name of an American oil retail brand. Its flagship product is its fuel "Texaco with Techron". It also owns the Havoline motor oil brand.... |
Schwedeneck A* | CGS Monotower | 25 m | North Sea (D) | DORIS/IMS |
| 22 | 1983 | Texaco Texaco Texaco is the name of an American oil retail brand. Its flagship product is its fuel "Texaco with Techron". It also owns the Havoline motor oil brand.... |
Schwedeneck B* | CGS Monotower | 16 m | North Sea (D) | DORIS/IMS |
| 23 | 1984 | Mobil Mobil Mobil, previously known as the Socony-Vacuum Oil Company, was a major American oil company which merged with Exxon in 1999 to form ExxonMobil. Today Mobil continues as a major brand name within the combined company, as well as still being a gas station sometimes paired with their own store or On... |
Statfjord C | Condeep Condeep Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise... 4 shafts |
145 m | North Sea (N) | NC/Olac Olsen |
| 24 | 1984 | Global Marine | Super CIDS | CGS caisson, Island | 16 m | Beaufort Sea | ? |
| 25 | 1986 | Statoil 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... |
Gullfaks A 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... |
Condeep Condeep Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise... 4 shafts |
135 m | North Sea (N) | NC/Olav Olsen |
| 26 | 1987 | Statoil 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... |
Gullfaks B 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... |
Condeep Condeep Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise... 3 shafts |
141 m | North Sea (N) | NC/Olav Olsen |
| 27 | 1988 | Norsk Hydro] | Oseberg A | Condeep Condeep Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise... 4 shafts |
109 m | North Sea (N) | NC/Olav Olsen |
| 28 | 1989 | Statoil 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... |
Gullfaks C 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... |
Condeep Condeep Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise... 4 shafts |
216 m | North Sea (N) | NC/olav Olsen |
| 29 | 1989 | Hamilton Bros | N. Ravenspurn | CGS 3 shafts | 42 m | North Sea (UK) | Arup Arup Arup is a global professional services firm headquartered in London, United Kingdom which provides engineering, design, planning, project management and consulting services for all aspects of the built environment. The firm is present in Africa, the Americas, Australasia, East Asia, Europe and the... |
| 30 | 1989 | Phillips Phillips Petroleum Phillips Petroleum Company was founded in 1917 by L.E. Phillips and Frank Phillips, of Bartlesville, Oklahoma. Their younger brother Waite Phillips was the benefactor of Philmont Scout Ranch.... |
Ekofisk P.B | CGS Protection Ring | 75 m | North Sea (N) | DORIS |
| 31 | 1996 | Elf Congo | N'Kossa | Concrete Barge | 170 m | Congo | BOS/Bouygues |
| 32 | 1993 | Shell Royal Dutch Shell Royal Dutch Shell plc , commonly known as Shell, is a global oil and gas company headquartered in The Hague, Netherlands and with its registered office in London, United Kingdom. It is the fifth-largest company in the world according to a composite measure by Forbes magazine and one of the six... |
NAM F3-FB | CGS 3 shafts | 43 m | North Sea (NL) | Hollandske Bet. |
| 33 | 1992 | Saga Saga Petroleum Saga Petroleum was a Norwegian upstream petroleum company established in 1972 that was acquired by Norsk Hydro in 1999. Since October 2007 it is a part of Statoil. The company was the only fully private oil company in Norway. It had partial ownership in 60 oil field licenses and was operator of 18... |
Snorre Concrete Foundation Templates (CFT) | 3 cells suction anchores | 310 m | North Sea (N) | NC/Olav Olsen |
| 34 | 1993 | Statoil 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... |
Sleipner A Sleipner A offshore platform Sleipner A is a combined accommodations, production and processing offshore platform at the Sleipner East gas field in the Norwegian sector of the North Sea... |
Condeep Condeep Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise... 4 shafts |
82 m | North Sea (N) | NC/Olav Olsen |
| 35 | 1993 | Shell Royal Dutch Shell Royal Dutch Shell plc , commonly known as Shell, is a global oil and gas company headquartered in The Hague, Netherlands and with its registered office in London, United Kingdom. It is the fifth-largest company in the world according to a composite measure by Forbes magazine and one of the six... |
Draugen | Condeep Condeep Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise... Monotower |
251 m | North Sea (N) | NC/Olav Olsen |
| 36 | 1994 | Conoco | Heidrun | Condeep Condeep Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise... |
350 m | North Sea (N) | NC/Olav Olsen |
| 37 | 1996 | BP BP BP p.l.c. is a global oil and gas company headquartered in London, United Kingdom. It is the third-largest energy company and fourth-largest company in the world measured by revenues and one of the six oil and gas "supermajors"... |
Harding Harding oilfield The Harding oilfield is a small oil field operated by BP, in the North Sea block 9/23b, approximately North-East of Aberdeen and in of water.-Discovery and development:... |
CGS | 109 m | North Sea (UK) | Taylor Wood Eng. |
| 38 | 1995 | Shell Royal Dutch Shell Royal Dutch Shell plc , commonly known as Shell, is a global oil and gas company headquartered in The Hague, Netherlands and with its registered office in London, United Kingdom. It is the fifth-largest company in the world according to a composite measure by Forbes magazine and one of the six... |
Troll A | Condeep Condeep Condeep refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway. A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise... 4 shafts |
303 m | North Sea (N) | NC/Olav Olsen |
| 39 | 1995 | Conoco | Heidrun TLP | Concrete TLP | 350 m | North Sea (N) | NC/Olav Olsen |
| 40 | 1995 | Norsk Hydro Norsk Hydro Norsk Hydro ASA is a Norwegian aluminium and renewable energy company, headquartered in Oslo. Hydro is the fourth largest integrated aluminium company worldwide. It has operations in some 40 countries around the world and is active on all continents. The Norwegian state holds a 43.8 percent... |
Troll B | Semisub | 325 m | North Sea (N) | DORIS |
| 41 | 1996 | Esso Esso Esso is an international trade name for ExxonMobil and its related companies. Pronounced , it is derived from the initials of the pre-1911 Standard Oil, and as such became the focus of much litigation and regulatory restriction in the United States. In 1972, it was largely replaced in the U.S. by... |
West Tuna | CGS 3 shafts | 61 m | Australia | Kinhill/DORIS |
| 42 | 1996 | Esso Esso Esso is an international trade name for ExxonMobil and its related companies. Pronounced , it is derived from the initials of the pre-1911 Standard Oil, and as such became the focus of much litigation and regulatory restriction in the United States. In 1972, it was largely replaced in the U.S. by... |
Bream B | CGS 1 shaft | 61 m | Australia | Kinhill/DORIS |
| 43 | 1996 | Ampolex | Wandoo | CGS 4 shafts | 54 m | Australia | Arup Arup Arup is a global professional services firm headquartered in London, United Kingdom which provides engineering, design, planning, project management and consulting services for all aspects of the built environment. The firm is present in Africa, the Americas, Australasia, East Asia, Europe and the... |
| 44 | 1997 | Mobil Mobil Mobil, previously known as the Socony-Vacuum Oil Company, was a major American oil company which merged with Exxon in 1999 to form ExxonMobil. Today Mobil continues as a major brand name within the combined company, as well as still being a gas station sometimes paired with their own store or On... |
Hibernia Hibernia (oil field) Hibernia is an oil field in the North Atlantic Ocean, approximately east-southeast of St. John's, Newfoundland, Canada.The production platform Hibernia is the world's largest oil platform and consists of a 37,000-tonne integrated topsides facility mounted on a 600,000-tonne gravity base structure... |
CGS 4 shafts | 80 m | Canada | DORIS |
| 45 | 1999 | Amerada Hess | South Arne | CGS 1 shaft | 60 m | North Sea (DK) | Taylor Woodrow |
| 46 | 2000 | Shell Royal Dutch Shell Royal Dutch Shell plc , commonly known as Shell, is a global oil and gas company headquartered in The Hague, Netherlands and with its registered office in London, United Kingdom. It is the fifth-largest company in the world according to a composite measure by Forbes magazine and one of the six... |
Malampaya | CGS 4 shafts | 43 m | Philippines | Arup Arup Arup is a global professional services firm headquartered in London, United Kingdom which provides engineering, design, planning, project management and consulting services for all aspects of the built environment. The firm is present in Africa, the Americas, Australasia, East Asia, Europe and the... |
| 47 | 2005 | Sakhalin Energy Investment Company Ltd. (SEIC) | Lunskoye A | CGS 4 shafts | 48 m | Sakhalin (R) | AK/GMAO |
| 48 | 2005 | Sakhalin Energy Investment Company Ltd. (SEIC) | Sakhalin PA-B | CGS 4 shafts | 30 m | Sakhalin (R) | AK/GMAO |
| 49 | 2008 | ExxonMobil 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... |
Adriatic LNG Adriatic LNG terminal The Adriatic LNG terminal is a liquid natural gas offshore terminal offshore near Rovigo, Italy in the northern Adriatic. It is the world's first offshore gravity-based structure LNG regasification terminal. The terminal is operated by Qatar Terminal Limited, a subsidiary of Qatar Petroleum,... |
LNG terminal | 29 m | Adriatic Sea (I) | AK/GMAO |
| 50 | 2008 | MPU Heavy Lifter (MPU filed for bankruptcy before completion, it was thereafter demolished) | Heavy Lift Vessel | LWA | n/a | na | Olav Olsen |