A
jack-up rig is a type of mobile platform that is able to stand still on the
sea floor, resting on a number of supporting legs. The most popular designs use 3 independent legs, although some jackups have 4 legs or more. On "mat-type" jackups the legs are connected to a submerged hull.
Operation
A jackup is a floating barge fitted with long support legs that can be raised or lowered. The jackup is towed (or self propelled) onto location with its legs up and the barge section floating on the water. Upon arrival at the drilling 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 seabottom so they will not penetrate further while operations are carried out. After preloading, the jacking system is used to raise the entire barge and drilling structure 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 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.
Types
Drilling platforms
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 any other type of mobile offshore
drilling rig. Other types of offshore rigs include
semi-submersibles (which float on pontoon-like structures) and
drillships, which are ship-shape vessels with rigs mounted in the centers. These rigs drill through holes in the drillship hulls, known as moon pools.
Barges
Jackup rigs also refer to specialized barges 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.
See also
Crane vessel
TIV Resolution
External links
Jackup Units: A technical Primer for the Offshore Industry Professional
References
Category:Oil platforms
Category:Ship types
Category:Petroleum production