The Troll A platform is a Condeep gravity-based structure offshore natural gas platform in the Troll gas field off the west coast of

Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of the Kingdom of ...

. Built from

reinforced concrete Reinforced concrete, also called ferroconcrete or ferro-concrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ...

, , it was the tallest structure 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 history. The platform was a televised sensation when it was towed into the

North Sea The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium, and France. A sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian Se ...

in 1995, where it is now operated by

Equinor Equinor ASA (formerly Statoil and StatoilHydro) is a Norwegian multinational energy company headquartered in Stavanger, Norway. It is primarily a petroleum company, petroleum company operating in 36 countries with additional investments in renew ...

. It is also the heaviest object moved and the object with the second highest displacement at 1.2 million tons (the object with the highest displacement is the Gullfaks C, which had a displacement approaching 1.5 million tons). Troll A was towed from the afternoon 10 May 1995 until the platform was in place 17 May 1995. It was lowered to the seabed in 303 meters of water, and had penetrated 36 meters into the soil by 19 May 1995. It was self-supporting with no further mooring required.

Dimensions

The Troll A platform has an overall height of , weighs 683,600 tons (1.2 million tons with ballast) and has the distinction of being the tallest structure ever moved by mankind. The platform stands on four legs extending down to the sea floor 303 meters (994 feet) below the surface of the sea, and the leg containing the import and export risers has an elevator that takes over nine minutes to travel from the platform above the waves to the sea floor. National Geographic Channel production, documentary 2007(?), rebroadcast 2009-10-02, 12-13:00 hrs EDST (Comcast Cable Television system) The legs must be able to withstand intense pressures, so the walls of Troll A's legs are over 1 metre thick and are made of steel-reinforced concrete that was formed in one continuous poura lengthy process that takes 20 minutes per 5 cm laid. Each leg is a mathematically joined composite of several conical cylinders that flares out smoothly to greater diameters at the top and bottom, so each support is somewhat wasp-waisted when viewed in profile and circular in any cross-section (see picture at right). The four legs are joined by a "chord shortener" (not present in the picture at right), a reinforced concrete box connecting the legs that damps out any potentially destructive wave-leg

resonance Resonance is a phenomenon that occurs when an object or system is subjected to an external force or vibration whose frequency matches a resonant frequency (or resonance frequency) of the system, defined as a frequency that generates a maximu ...

s by retuning the legs' natural frequencies. Each leg is also sub-divided along its length into compartments a third of the way from each end which act as independent water-tight compartments. The legs use groups of six tall vacuum-anchors holding them fixed in the mud of the sea floor.

Construction

Troll A was built by Norwegian Contractors for Norske Shell, with base construction beginning in September 1991 at a cost of 4150 million NOK, or approximately US$650 million at the time. The base and the deck were built separately, and were joined in 1998 while the base was partially submerged. The base is a Condeep gravity base structure built from

. The Troll platform was towed over from Vats, in the northern part of

Rogaland Rogaland () is a Counties of Norway, county in Western Norway, bordering the North Sea to the west and the counties of Vestland to the north, Telemark to the east and Agder to the east and southeast. As of 1 January 2024, it had a population of 49 ...

, to the Troll field, north-west of

Bergen Bergen (, ) is a city and municipalities of Norway, municipality in Vestland county on the Western Norway, west coast of Norway. Bergen is the list of towns and cities in Norway, second-largest city in Norway after the capital Oslo. By May 20 ...

. The tow took seven days.

Expansion

In the autumn of 2010 the Troll A platform was expanded with a new module. This module contains living quarters and a new control room. The new control room and expanded facilities are needed to support new compressors. These compressors are needed due to the dropping reservoir pressure in the wells. On 18 June 2013 the new support module ''M12'' for compressors 3 and 4 was lifted on board Troll A. The increased electricity consumption of these compressors required new power cables from shore, and due to grid constraints the platform is cut off from shore power if a grid emergency arises.

Operation

Gas rises from 40 wells and is exported through a number of pipes to a processing plant at Kollsnes. Troll A is scheduled to receive two additional gas compressors to increase production volume and compensate for dropping reservoir pressure in the wells.

World records

In 1996, the platform set the Guinness World Record for the largest offshore gas platform. In 2006, the 10th anniversary of Statoil's operatorship of Troll gas production was celebrated with a concert by Katie Melua held at the base of one of the hollow legs of the platform. The concert set a new

world record A world record is usually the best global and most important performance that is ever recorded and officially verified in a specific skill, sport, or other kind of activity. The book ''Guinness World Records'' and other world records organizatio ...

for the deepest underwater concert, at below sea level.

References

External links

*
Offshore-Technology.com: Troll
{{DEFAULTSORT:Troll A Platform Natural gas platforms Natural gas industry in Norway North Sea energy Equinor 1996 establishments in Norway