A jackup rig or a self-elevating unit is a type of mobile platform that consists of a buoyant hull 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 or heavy lift ships for transportation.
Jackup platforms are used as exploratory drilling platforms and offshore and wind farm service platforms. 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.
An early design was the DeLong platform, designed by Leon B. DeLong. 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 with McDermott, which built the DeLong-McDermott No.1 in 1954 for Humble Oil. 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, 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 and featured three electro-mechanically-operated lattice type legs. Built on the shores of the Mississippi river by the LeTourneau Company, it was launched in December 1955. The Scorpion was put into operation in May 1956 off Port Aransas, Texas. The second, also designed by LeTourneau, was called Vinegaroon. More details