__NOTOC__ A tension-leg platform (TLP) or extended tension leg platform (ETLP) is a vertically moored floating structure normally used for the offshore production of

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturate ...

or gas, and is particularly suited for water depths greater than 300 metres (about 1000 ft) and less than 1500 metres (about 4900 ft). Use of tension-leg platforms has also been proposed for offshore wind turbines. The platform is permanently moored by means of tethers or tendons grouped at each of the structure's corners. A group of tethers is called a tension leg. A feature of the design of the tethers is that they have relatively high

axial Axial may refer to: * one of the anatomical directions describing relationships in an animal body * In geometry: :* a geometric term of location :* an axis of rotation * In chemistry, referring to an axial bond * a type of modal frame, in music * ...

stiffness Stiffness is the extent to which an object resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is. Calculations The stiffness, k, of a b ...

(low elasticity), such that virtually all vertical motion of the platform is eliminated. This allows the platform to have the production

wellhead A wellhead is the component at the surface of an oil or gas well that provides the structural and pressure-containing interface for the drilling and production equipment. The primary purpose of a wellhead is to provide the suspension point and ...

s on deck (connected directly to the subsea wells by rigid risers), instead of on the

seafloor The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

. This allows a simpler well completion and gives better control over the production from the

or gas

reservoir A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including control ...

, and easier access for downhole intervention operations. TLPs have been in use since the early 1980s. The first tension leg platformReconversion d’une plate-forme offshore
/ref> was built for Conoco's Hutton field in the North Sea in the early 1980s. The hull was built in the dry-dock at Highland Fabricator's Nigg yard in the north of Scotland, with the deck section built nearby at McDermott's yard at Ardersier. The two parts were mated in the Moray Firth in 1984. The Hutton TLP was originally designed for a service life of 25 years in Nord Sea depth of 100 to 1000 metres. It had 16 tension legs. Its weight varied between 46,500 and 55,000 tons when moored to the seabed, but up to 61,580 tons when floating freely. The total area of its living quarters was about 3,500 square metres and accommodated over a 100 cabins though only 40 people were necessary to maintain the structure in place. The hull of the Hutton TLP has been separated from the topsides. Topsides have been redeployed to the Prirazlomnoye field in the

Barents Sea The Barents Sea ( , also ; no, Barentshavet, ; russian: Баренцево море, Barentsevo More) is a marginal sea of the Arctic Ocean, located off the northern coasts of Norway and Russia and divided between Norwegian and Russian ter ...

, while the hull was reportedly sold to a project in the Gulf of Mexico (although the hull has been moored in Cromarty Firth since 2009). Larger TLPs will normally have a full drilling rig on the platform with which to drill and intervene on the wells. The smaller TLPs may have a workover rig, or with most recent TLPs, production wellheads located at remote drillcentres subsea. The deepest (E)TLPs measured from the sea floor to the surface are: * Big Foot ETLP * Magnolia ETLP. Its total height is some . * Marco Polo TLP * Neptune TLP * Kizomba A TLP * Ursa TLP. Its height above surface is making a total height of .Alexander's Gas & Oil Connections – Shell's Ursa deep water TLP begins production
/ref> * Allegheny TLP * W. Seno A TLP

Use for wind turbines

Although the

Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a Private university, private Land-grant university, land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern t ...

and the

National Renewable Energy Laboratory The National Renewable Energy Laboratory (NREL) in the US specializes in the research and development of renewable energy, energy efficiency, energy systems integration, and sustainable transportation. NREL is a federally funded research and ...

explored the concept of TLPs for offshore wind turbines in September 2006, architects had studied the idea as early as 2003. Earlier offshore wind turbines cost more to produce, stood on towers dug deep into the ocean floor, were only possible in depths of at most , and generated 1.5 megawatts for onshore units and 3.5 megawatts for conventional offshore setups. In contrast, TLP installation was calculated to cost a third as much. TLPs float, and researchers estimate they can operate in depths between 100 and and farther away from land, and they can generate 5.0 megawatts.Floating Ocean Windmills Designed to Generate More Power
/ref>

Computer simulation Computer simulation is the process of mathematical modelling, performed on a computer, which is designed to predict the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be dete ...

s project that in a

hurricane A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depe ...

TLPs would shift 0.9 m to 1.8 m and the turbine blades would cycle above wave peaks. MIT and NREL researchers say dampers could be used to reduce motion in the event of a natural disaster. MIT and NREL researchers plan to install a half-scale prototype south of

Cape Cod Cape Cod is a peninsula extending into the Atlantic Ocean from the southeastern corner of mainland Massachusetts, in the northeastern United States. Its historic, maritime character and ample beaches attract heavy tourism during the summer mon ...

. Sclavounos said, "We'd have a little unit sitting out there to show that this thing can float and behave the way we're saying it will." Blue H Technologies of the

Netherlands ) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherl ...

deployed the world's first

floating wind turbine A floating wind turbine is an offshore wind turbine mounted on a floating structure that allows the turbine to generate electricity in water depths where fixed-foundation turbines are not feasible. Floating wind farms have the potential to signif ...

on a tension-leg platform, off the coast of Apulia,

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical ...

in December 2007.Deep water wind turbines
'' The Institution of Engineering and Technology'', 18 October 2010, accessed 6 November 2011 The prototype was installed in waters deep in order to gather test data on wind and sea conditions, and was decommissioned at the end of 2008. The turbine utilized a tension-leg platform design and a two-bladed turbine. Seawind Ocean Technology B.V., which was established by Martin Jakubowski and Silvestro Caruso - the founders of Blue H Technologies, acquired the proprietary rights to the two-bladed floating turbine technology developed by Blue H Technologies.

References

{{Reflist, 2

Use for wind turbines

See also

References

Further reading