Movable structure that is anchored to the seabed and used at depths of 100 to 500 m; it is mounted on pontoons submerged at about 30 m to provide stability.
Structure that is mainly used at moderate depths (up to 400 m); it rests on the seabed on pillars buried deep in the sea floor.
pier
Structure that extends into the sea from a land-based installation; it is used for land drilling extending offshore (about 3 m deep).
emergency support vessel
Floating structure equipped with specialized equipment; it is used for rescue operations on drilling rigs.
jack-up platform
Movable structure that is used in shallow water (between 20 and 100 m); it is raised above sea level on retractable pillars resting on the ocean floor.