Semi-Submersible Platforms — Floating rigs for deeper offshore drilling.

A semi-submersible platform is a highly advanced type of mobile offshore drilling unit (MODU) designed for deepwater drilling operations. Unlike a jack-up rig, which rests on the seabed, a semi-submersible is a floating vessel that maintains its position in the water using a combination of ballast tanks and a complex mooring or dynamic positioning system. It is a work of engineering art, designed to operate in harsh weather conditions and in depths where a jack-up rig cannot reach.

How They Work
A semi-submersible platform consists of a deck, on which the drilling equipment is located, and a series of large, submerged pontoons and columns. When the rig is being towed to a location, the pontoons are empty. Once on site, the pontoons are partially filled with water, which causes the rig to sink to a predetermined depth. The rig then operates with most of its structure submerged, which provides a high degree of stability, as it is less affected by surface waves.

The rig is then held in place by a series of anchors and mooring lines, or by an advanced dynamic positioning (DP) system, which uses computer-controlled thrusters to hold the rig in a precise location.

Key Advantages and Applications
The primary advantage of a semi-submersible platform is its ability to operate in much deeper waters, typically ranging from a few hundred feet to thousands of feet. This makes it an ideal choice for:

Deepwater Exploration: Semi-submersibles are a key tool for exploring for new oil and natural gas reserves in the vast, deepwater regions of the world.

Drilling and Production: They are used to drill both exploration wells and development wells and can also be used as a production platform in some cases.

The ability to operate in deep water and in harsh weather conditions makes the semi-submersible platform a vital part of the offshore energy industry.