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. Built from

reinforced concrete Reinforced concrete (RC), also called reinforced cement concrete (RCC) and ferroconcrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having hig ...

, , 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 in 1996, where it is now operated by Equinor. It is often incorrectly referenced as the heaviest object ever moved as well, but it is actually the second heaviest after another Condeep Oil platform the Gullfaks C, which had a displacement approaching 1.5 million tons in comparison with Troll A's 1.2 million.

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 and second heaviest structure ever moved by humankind. 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 resonances 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, Vestfold og Telemark to the east and Agder to the east and southeast. In 2020, it had a population of 47 ...

, to the Troll field, north-west of Bergen. 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 the new compressors (a third and fourth are planned and being installed in 2014). 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 ''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a reference book published annually, listing world ...

for the largest offshore gas platform. In 2006, the 10th anniversary of

Statoil Equinor ASA (formerly Statoil and StatoilHydro) is a Norwegian state owned enterprise, state-owned multinational energy company headquartered in Stavanger. It is primarily a petroleum company, petroleum company, operating in 36 countries with ad ...

'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 for the deepest underwater concert, at below sea level.

References

External links

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