Mobile offshore drilling or installation unit with retractable legs that are lowered to the seabed, lifting the hull clear of the water surface for operations.
A jack-up rig (or self-elevating unit) is a mobile offshore unit comprising a buoyant triangular or rectangular hull (mat or independent-leg) fitted with three or four lattice or cylindrical legs. In transit, the legs are raised and the hull floats; on location, the legs are hydraulically or electrically jacked down to the seabed, and the hull is elevated above wave action to provide a stable working platform. Operational water depths are typically up to 120–150 m for drilling jack-ups, though enhanced designs reach 170 m.
Drilling jack-ups are employed for exploration, appraisal, and development wells on the continental shelf. A separate and growing market uses purpose-designed wind-farm installation jack-ups (WIJUs) to install turbine foundations, transition pieces, and nacelles in shallower waters; these carry large rotating cranes rather than drilling derricks. Leading contractors include Valaris, Noble, Borr Drilling (drilling), and Cadeler, Eneti (wind installation).
Jack-up rigs are classified under the IMO MODU Code (Code for the Construction and Equipment of Mobile Offshore Drilling Units), made mandatory under SOLAS Chapter XI-2 for security, with structural design governed by classification society rules (ABS, DNV, Lloyd's Register). Flag State requirements under SOLAS Chapter II-1 (stability and buoyancy when afloat) and MARPOL apply during tow transits. ISM Code compliance (SOLAS Chapter IX) is mandatory for the owning company.