Jackup rig at a glance
- Category
- Bottom-supported MODU (mobile offshore drilling unit)
- How it stays put
- Three or more legs jacked down to rest on the seabed
- Water depth
- Shallow water — up to roughly 120–150 m
- Main types
- Independent-leg vs mat-supported
- Notable
- The most common offshore rig type worldwide
Among offshore rig types, the jackup occupies the shallow-water tier — and it dominates it. A jackup combines two ideas: it's a barge-like hull that can be towed or sailed like a vessel, and a self-elevating platform that, once on location, lifts itself above the sea on legs planted in the seabed. That combination makes it mobile enough to relocate between wells and stable enough to drill from a fixed, dry working deck.
How a jackup works
The operating sequence is the defining feature of the type:
- Transit. With its legs raised, the jackup floats — towed by tugs or self-propelled — to the well location, hull in the water like any barge.
- Jacking down. On location, the rig lowers its legs (driven by a rack-and-pinion or hydraulic jacking system) until they touch and bite into the seabed.
- Preloading. The legs are loaded — often by taking on seawater ballast — to firmly seat the footings in the soil and confirm the seabed will bear the rig's full weight.
- Elevating the hull. The jacking system then lifts the entire hull up the legs, raising the working deck well above the highest expected waves — the "air gap."
- Drilling. Now a stable, fixed platform, the jackup drills the well, typically cantilevering its drilling package out over an existing wellhead or platform.
Because the hull is lifted clear of the water, the jackup behaves like a fixed structure while drilling — no heave, no need for the heave-compensation and dynamic-positioning systems that floaters require. That stability is a big reason jackups are so cost-effective in shallow water.
Why "bottom-supported" caps the water depth. A jackup's legs have to physically reach the seabed and still leave enough length above water for the hull and an adequate air gap. That geometry limits jackups to shallow water — generally up to about 120–150 m. Beyond that, drilling moves to floating rigs like semisubmersibles and drillships.
Independent-leg vs mat-supported
Jackups come in two foundation styles, chosen mainly by seabed conditions:
| Type | How it bears load | Best for |
|---|---|---|
| Independent-leg | Each leg ends in its own footing (a "spudcan") that penetrates the soil individually | Most conditions, including firmer or uneven seabeds; the dominant modern design |
| Mat-supported | The legs connect to a single large bottom mat that spreads load over a wide area | Soft, low-bearing seabeds (e.g., soft mud) where a spread footprint prevents sinking |
Independent-leg jackups are the more versatile and common design today, with each leg's spudcan footing penetrating the seabed on its own. Mat-supported units shine where the bottom is too soft to support concentrated point loads, distributing the rig's weight across a broad mat instead.
Where jackups are used
Jackups drill the world's shallow-water wells — across the Gulf of Mexico shelf, the North Sea, the Middle East, Southeast Asia, West Africa, and elsewhere. They're used both to drill exploration and development wells and to perform workover and intervention on existing shallow-water wellheads and fixed platforms, often cantilevering their drilling package over a platform to reach its wells. Their mobility lets an operator move a single jackup across a series of nearby locations far more cheaply than committing a floating rig.
On board, the chain of command mirrors any rig: the contractor's Toolpusher runs the rig and crews while the operator's Company Man runs the well, with a Driller and roughnecks on the floor. The marine and jacking systems simply add an offshore layer to that structure.
Common questions
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