Troll-A Platform: Largest Object Ever Moved by Man

Mar 12, 2013 4 comments

The Troll A platform is an offshore natural gas platform in the Troll gas field off the west coast of Norway. At 1.2 million ton ballasted under tow, 472 meters high, with underwater concrete structure at 369 meters, and dry weight of 656,000 tons, the Troll A platform is a majestic piece of design and construction. Not only is Troll A among the largest and most complex engineering projects in history, it is the largest object ever to be moved by man across the surface of the Earth. The platform was a televised sensation when it was towed into the North Sea in 1996, where it is now operated by Statoil.

Normally a platform's legs are transported on their side and then - supported by flotation devices - are dropped into place. In the case of Troll A, however, the whole platform was assembled in one location, and then floated out to sea. The Troll platform was towed over 200 kilometers from Vats, in the northern part of Rogaland, to the Troll field, 80 kilometers north-west of Bergen. The tow took seven days.


The platform stands on the sea floor 303 meters below the surface of the sea and one of the concrete cylindrical legs has an elevator that takes over nine minutes to travel from the platform above the waves to the sea floor. The walls of Troll A's legs are over 1 meter thick made of steel reinforced concrete formed in one continuous pour. The four legs are joined by a "Chord shortener", a reinforced concrete box interconnecting the legs, but which has the designed function of damping out unwanted potentially destructive wave-leg resonances. 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 40 meters tallvacuum-anchors holding it fixed in the mud of the sea floor.

In 1996 the platform set the Guinness World Record for 'largest offshore gas platform'. The title now belongs to the Petronius Platform in the Gulf of Mexico which stands 2,000 feet (610 m) above the ocean floor.




Inside one of the Troll platform's legs


Comparison of Troll Platform & Eiffel Tower




Sources: Wikipedia, Dark Roasted Blend


  1. I watched a program on tv in the mid 90s about this. I have been looking for it since then so I could rent or buy the dvd. It covered the building and tow from the fjord it was built in out to sea. If the tow had gone wrong and the rig fell to the sea floor, they said it would cause a tremor between 4 and 5 on the Richter scale. If anyone has information on the name of the program, etc, I would really appreciate the information. The episode was that good. Thanks!

    1. Hi,

      You will now be able to find this Troll A movie on Youtube.
      It was made by Discovery channel and was called "Skyscraper At Sea"
      The movie clip on youtube is called: Troll A natural gas platform - placed in the north sea 1995
      This is another video about this platform:

      On the web pages in the link below you will also find some information about the construction and towing of Troll A Platform to field.

      The towing of the Platform started in Vats, Yrkjefjorden Norway 10th May 1995.

      I was working onboard one of the Back-up tow vessel called "Mærsk Master" during the tow from the fjords to Troll Field.
      I was working for the company Dolphin DOC AS as an ROV Pilot at that time and we had 3 ROV's (Remotely operated vehicles) onboard the vessel. Those ROV's was use in the fjords to release all the anchor chains that held the platform in position during construction period in Vats, Yrkjefjorden.
      The ROV'S also played an important role when the platform was finally placed in position on the Troll field 17th May 1995.

      We performed a lot of dives during that period of resting the platform on the seabed at 303 meters.

      The film team from Discovery channel that made this film about Troll A also stayed onboard the
      vessel "Mærsk Master".

      This was really memorable moments in my offshore career.

      Espen Arem

    2. scandis@cinci.rr.comMarch 24, 2015 at 12:31 AM

      the name of the program was skyscraper at sea,There is a DVD avalible from the discovery channel.

  2. I'm not sure about the tremor theory but I'm sure a big tsunami


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