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A jackup rig or a self-elevating unit is a type of mobile platform that consists of a buoyant
hull Hull may refer to: Structures * Chassis, of an armored fighting vehicle * Fuselage, of an aircraft * Hull (botany), the outer covering of seeds * Hull (watercraft), the body or frame of a ship * Submarine hull Mathematics * Affine hull, in affi ...
fitted with a number of movable legs, capable of raising its hull over the surface of the sea. The buoyant hull enables transportation of the unit and all attached machinery to a desired location. Once on location the hull is raised to the required elevation above the sea surface supported by the sea bed. The legs of such units may be designed to penetrate the sea bed, may be fitted with enlarged sections or footings, or may be attached to a bottom mat. Generally jackup rigs are not self-propelled and rely on
tugs A tugboat or tug is a marine vessel that manoeuvres other vessels by pushing or pulling them, with direct contact or a tow line. These boats typically tug ships in circumstances where they cannot or should not move under their own power, suc ...
or
heavy lift ship A heavy-lift ship is a vessel designed to move very large loads that cannot be handled by normal ships. They are of two types: *''Semi-submersible'' ships that take on water ballast to allow the load—usually another vessel—to be floated o ...
s for transportation. Jackup platforms are almost exclusively used as exploratory oil and gas drilling platforms and as offshore and wind farm service platforms. Jackup rigs can either be triangular in shape with three legs or square in shape with four legs. Jackup platforms have been the most popular and numerous of various mobile types in existence. The total number of jackup drilling rigs in operation numbered about 540 at the end of 2013. The tallest jackup rig built to date is the Noble Lloyd Noble, completed in 2016 with legs 214 metres (702 feet) tall.


Name

Jackup rigs are so named because they are self-elevating with three, four, six and even eight movable legs that can be extended (“jacked”) above or below the hull. Jackups are towed or moved under self propulsion to the site with the hull lowered to the water level, and the legs extended above the hull. The hull is actually a water-tight barge that floats on the water’s surface. When the rig reaches the work site, the crew jacks the legs downward through the water and into the sea floor (or onto the sea floor with mat supported jackups). This anchors the rig and holds the hull well above the waves.


History

An early design was the DeLong platform, designed by
Leon B. DeLong Leon, Léon (French) or León (Spanish) may refer to: Places Europe * León, Spain, capital city of the Province of León * Province of León, Spain * Kingdom of León, an independent state in the Iberian Peninsula from 910 to 1230 and again f ...
. In 1949 he started his own company, DeLong Engineering & Construction Company. In 1950 he constructed the ''DeLong Rig No. 1'' for Magnolia Petroleum, consisting of a barge with six legs. In 1953 DeLong entered into a
joint-venture A joint venture (JV) is a business entity created by two or more parties, generally characterized by shared ownership, shared returns and risks, and shared governance. Companies typically pursue joint ventures for one of four reasons: to acce ...
with McDermott, which built the ''DeLong-McDermott No.1'' in 1954 for
Humble Oil Humble Oil and Refining Co. is a defunct American oil company founded in 1911 in Humble, Texas. In 1919, a 50% interest in Humble was acquired by the Standard Oil of New Jersey which acquired the rest of the company in September 1959. The Humbl ...
. This was the first mobile offshore drilling platform. This barge had ten legs which had ''spud cans'' to prevent them from digging into the seabed too deep. When DeLong-McDermott was taken over by the
Southern Natural Gas Company Southern Natural Gas Company, headquartered in Birmingham, Alabama, is a natural gas pipeline company that was founded in 1928 and is currently a division of Kinder Morgan. The company was a division of Birmingham-based Sonat Inc. until 1999 when ...
, which formed The Offshore Company, the platform was called ''Offshore No. 51''. In 1954, Zapata Offshore, owned by George H. W. Bush ordered the ''Scorpion''. It was designed by
R. G. LeTourneau Robert Gilmour LeTourneau (November 30, 1888 – June 1, 1969), born in Richford, Vermont, he was a prolific inventor of earthmoving machinery and the founder of LeTourneau Technologies, Inc. His factories supplied LeTourneau machines which rep ...
and featured three electro-mechanically-operated lattice type legs. Built on the shores of the
Mississippi river The Mississippi River is the List of longest rivers of the United States (by main stem), second-longest river and chief river of the second-largest Drainage system (geomorphology), drainage system in North America, second only to the Hudson B ...
by the LeTourneau Company, it was launched in December 1955. The ''Scorpion'' was put into operation in May 1956 off
Port Aransas Port Aransas ( ) is a city in Nueces County, Texas, United States. This city is 180 miles southeast of San Antonio. The population was 2,904 at the 2020 census. Port Aransas is the only established town on Mustang Island. It is located north of ...
, Texas. The second, also designed by LeTourneau, was called ''Vinegaroon''.


Operation

A jackup rig is a barge fitted with long support legs that can be raised or lowered. The jackup is maneuvered (self-propelled or by towing) into location with its legs up and the hull floating on the water. Upon arrival at the work location, the legs are jacked down onto the seafloor. Then "preloading" takes place, where the weight of the barge and additional ballast water are used to drive the legs securely into the sea bottom so they will not penetrate further while operations are carried out. After preloading, the jacking system is used to raise the entire barge above the water to a predetermined height or "air gap", so that wave, tidal and current loading acts only on the relatively slender legs and not on the barge hull. Modern jacking systems use a
rack and pinion A rack and pinion is a type of linear actuator that comprises a circular gear (the '' pinion'') engaging a linear gear (the ''rack''). Together, they convert rotational motion into linear motion. Rotating the pinion causes the rack to be driven ...
gear arrangement where the pinion gears are driven by hydraulic or electric motors and the rack is affixed to the legs. Jackup rigs can only be placed in relatively shallow waters, generally less than of water. However, a specialized class of jackup rigs known as premium or ultra-premium jackups are known to have operational capability in water depths ranging from 150 to 190 meters (500 to 625 feet).


Types


Mobile offshore Drilling Units (MODU)

This type of rig is commonly used in connection with oil and/or natural gas drilling. There are more jackup rigs in the worldwide offshore rig fleet than other type of mobile offshore
drilling rig A drilling rig is an integrated system that drills wells, such as oil or water wells, or holes for piling and other construction purposes, into the earth's subsurface. Drilling rigs can be massive structures housing equipment used to drill wa ...
. Other types of offshore rigs include
semi-submersibles Semi-submersible may refer to a self-propelled vessel, such as: * Heavy-lift ship, which partially submerge to allow their cargo (another ship) to float into place for transport * Narco-submarine, some of which remained partially on the surface * ...
(which float on pontoon-like structures) and drillships, which are ship-shaped vessels with rigs mounted in their center. These rigs drill through holes in the drillship hulls, known as moon pools.


Turbine Installation Vessel (TIV)

This type of rig is commonly used in connection with
offshore wind turbine Offshore wind power or offshore wind energy is the generation of electricity through wind farms in bodies of water, usually at sea. There are higher wind speeds offshore than on land, so offshore farms generate more electricity per amount of c ...
installation.


Barges

''Jackup rigs'' can also refer to specialized
barge Barge nowadays generally refers to a flat-bottomed inland waterway vessel which does not have its own means of mechanical propulsion. The first modern barges were pulled by tugs, but nowadays most are pushed by pusher boats, or other vessels. ...
s that are similar to an oil and gas platform but are used as a base for servicing other structures such as offshore wind turbines, long bridges, and drilling platforms. File:NewCarissa dismantled by KarlissaA and B July 2008 panorama merge.jpg, Jackup barges being used to dismantle a ship that was wrecked at sea. File:Scroby Sands Wind Farm 2981489897.jpg, Jackup barge servicing a
Vestas Vestas Wind Systems A/S is a Danish manufacturer, seller, installer, and servicer of wind turbines that was founded in 1945. The company operates manufacturing plants in Denmark, Germany, the Netherlands, Taiwan, India, Italy, Romania, the Un ...
V80-2 MW
wind turbine A wind turbine is a device that converts the kinetic energy of wind into electrical energy. Hundreds of thousands of large turbines, in installations known as wind farms, now generate over 650 gigawatts of power, with 60 GW added each year. ...
of the Scroby Sands wind farm.


See also

*
Crane vessel A crane vessel, crane ship or floating crane is a ship with a crane specialized in lifting heavy loads. The largest crane vessels are used for offshore construction. Conventional monohulls are used, but the largest crane vessels are often catam ...
*
Offshore geotechnical engineering Offshore geotechnical engineering is a sub-field of geotechnical engineering. It is concerned with foundation design, construction, maintenance and decommissioning for human-made structures in the sea.Dean, p. 1 Oil platforms, artificial island ...
*
Oil platform An oil platform (or oil rig, offshore platform, oil production platform, and similar terms) is a large structure with facilities to extract and process petroleum and natural gas that lie in rock formations beneath the seabed. Many oil platfor ...
*
Rack phase difference Rack Phase Difference (RPD) is a difference in the elevation between rack teeth of the chords of any single leg of a jackup rig with open truss-type legs. This type of jackup vessel operates with a rack and pinion drive system, as opposed to th ...
*
TIV Resolution TIV ''MPI Resolution'' (formerly TIV ''Mayflower Resolution'') is a wind turbine installation vessel deployed to install turbines at offshore wind farms. It was the first self-elevating Turbine Installation Vessel in the world. She can raise h ...


References

{{reflist Oil platforms Ship types