View source for Troll A platform

{{Short description|Natural gas rig off the coast of Norway}}
[[Image:Troll A Platform.jpg|thumb|A view from the South East of Troll A Platform.]]
The '''Troll A platform''' is a [[Condeep]] [[gravity-based structure]] offshore [[Oil platform|natural gas platform]] in the [[Troll gas field]] off the west coast of [[Norway]]. Built from [[reinforced concrete]], {{as of|2014|lc=y}}, 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.<ref name=opa20140102>{{cite web|title=Meet the Troll A platform, the largest object ever moved|url=http://oilpatchasia.com/2013/12/meet-the-troll-a-platform-the-largest-object-ever-moved/|publisher=Oil Patch Asia|access-date=2 January 2014}}</ref>  The platform was a televised sensation when it was towed into the [[North Sea]] in 1995, where it is now operated by [[Equinor]]. It is also the heaviest object moved and the object with the second highest displacement at 1.2 million tons<ref>{{Cite web|url=https://www.zmescience.com/other/offbeat-other/tallest-structure/|title = Troll A - the tallest moved structure in the world|date = 21 September 2015}}</ref> (the object with the highest displacement is the [[Gullfaks oil field|Gullfaks C]], which had a displacement approaching 1.5 million tons<ref>{{Cite web|url=https://www.guinnessworldrecords.com/world-records/467630-heaviest-man-made-object-moved|title = Heaviest man-made object moved}}</ref>). 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{{Citation needed|date=September 2023}}. It was self-supporting with no further mooring required{{Citation needed|date=September 2023}}.

==Dimensions==
[[Image:Oil platform Norway.jpg|right|thumb|Continuous [[Slip forming|slip formed]] [[gravity-based structure]] supports under construction in a Norwegian [[fjord]]. The tower cranes delivered concrete to the support cylinders during the continuous pour of concrete to create seamless walls.]]

The Troll A platform has an overall height of  {{Convert|472|m|ft|0}}, weighs 683,600 tons (1.2 million tons with ballast)<ref>{{cite web | title= Gas Machine - The ultimate move | work=[[Statoil]] | date=  2 October 2006| url=http://goodideas.statoil.com/gas-machine#/big-move }}</ref> 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.<ref name="NGSD">
<!-- Nat Geo Special Doc-->
National Geographic Channel production, documentary 2007(?), rebroadcast 2009-10-02, 12-13:00 hrs EDST (Comcast Cable Television system)
</ref>

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 [[slip forming|continuous pour]]{{snd}}a lengthy process that takes 20 minutes per 5&nbsp;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 waist|wasp-waisted]] when viewed in profile and circular in any cross-section (see picture at right).<ref name="NGSD" />

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]]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<!-- count may be off,  I didn't record this pgm to check recall; height is solid data --> {{convert|40|m}} tall [[vacuum-anchor]]s holding them fixed in the mud of the sea floor.<ref name="NGSD" />

==Construction==
Troll A was built by [[Norwegian Contractors]] for [[Royal Dutch Shell|Norske Shell]], with base construction beginning in September 1991<ref>
{{cite web | title=Structurae - Troll A Platform | url=http://en.structurae.de/structures/data/index.cfm?id=s0003286}}</ref> at a cost of 4150 million [[Norwegian krone|NOK]],<ref>
{{cite web | title=Great Structures of Europe | url=http://greatstructures.info/europe.htm}}</ref><ref>
<!-- this reference mentions 4150 BILLION, not million. This is conversion is clearly wrong -->{{cite web | title=Troll and Heidrun: end of an era or forerunners of a modern world? | url=http://www.offshore-mag.com/articles/print/volume-55/issue-8/news/general-interest/troll-and-heidrun-end-of-an-era-or-forerunners-of-a-modern-world.html | year=1995}}</ref> or approximately US$650 million at the time.<ref>
{{cite web | title=Exchange rate, US dollar (USD) | url=http://www.norges-bank.no/en/price-stability/exchange-rates/usd/aar/ | publisher=Norges Bank}}</ref> 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 [[reinforced concrete]].

The Troll platform was towed over {{convert|200|km}} from [[Vats, Rogaland|Vats]], in the northern part of [[Rogaland]], to the [[Troll oil field|Troll field]], {{convert|80|km}} north-west of [[Bergen, Norway|Bergen]]. The tow took seven days.<ref>{{cite web |last1=Eide |first1=Ole Jone |title=Troll A – giant move from fjord to field |url=https://equinor.industriminne.no/en/troll-a-giant-move-from-fjord-to-field/ |website=Equinor 50 years |date=13 June 2022 |publisher=Norwegian Petroleum Museum |access-date=21 November 2022}}</ref>

==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 the 18th of June, 2013, the new support module "''M12"'' for compressors 3 and 4 was lifted on board of 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.<ref>Øyvind Lie. "[http://www.tu.no/kraft/2011/09/27/troll-a-blir-b-kunde Troll A blir B-kunde]" ''[[Teknisk Ukeblad]]'', 27. september 2011. Accessed: 14 November 2013.</ref>

==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{{When|date=September 2023}} 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.<ref>{{cite web | title= Guinness World Records - largest offshore gas platform | work=[[Guinness World Records]] | date= 1996| url=http://www.guinnessworldrecords.com/records/science_and_technology/buildings/largest_offshore_gas_platform.aspx }}</ref>

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 [[Guinness World Records|world record]] for the deepest underwater concert, at {{convert|303|m}} below sea level.<ref>{{cite web | title= Melua's deep sea gig sets record | work=[[BBC News]] | date=  2 October 2006| url=https://news.bbc.co.uk/2/hi/entertainment/5396970.stm }}</ref>

==See also==
{{Portal|Norway|Energy}}
* [[HVDC Troll]]
* [[Ursa tension leg platform]], another, taller record-breaking platform
* [[Magnolia (oil platform)|Magnolia extended tension leg platform]], the world's deepest ETLP

==References==
{{Reflist}}

==External links==
* {{Structurae|id=20003286|title=Troll A Platform}}
* [http://www.offshore-technology.com/projects/troll/troll1.html Offshore-Technology.com: Troll]

{{Supertall}}
{{Authority control}}{{Coord|60|38|42.43|N|3|43|29.03|E|display=title}}{{DEFAULTSORT:Troll A Platform}}
[[Category:Natural gas platforms]]
[[Category:Natural gas industry in Norway]]
[[Category:North Sea energy]]
[[Category:Equinor]]
[[Category:1996 establishments in Norway]]