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Surviving offshore

Surviving offshore: oil rig support
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Surviving offshore: oil rig support

The spread of oil extraction to offshore fields has spawned a variety of specialist ships.  As exploration has moved into deeper waters, for instance in the North Sea, these have had to adapt to withstand more ferocious conditions.

Servicing the rigs

Drilling rigs and production platforms with comparatively large crews require regular supplies.  Oil rig supply vessels (ORSVs) have been developed to service these rigs.  Their superstructure is usually well forward and they have a long clear deck aft, on which pipes or other heavy equipment can be carried.  As well as supplies for those working on rigs, ORSVs also have tanks to carry concrete which is used to line drilling shafts and mud which lubricates the drill bit.  As oil exploration has moved further into deeper and stormier waters, ORSVs have grown bigger and more powerful to withstand the worst weather.  They also work as safety vessels, positioned off a platform to take action in case of an accident.  They will often have to ride out a storm whilst standing by a rig or platform.

Drilling in the deep

An impressive vessel built for oil exploration work is the drill ship.  Its large hull has a drilling rig built on it, with arrangements for the drill bit to pass through the hull.  As it is vital for the drill ship to stay in position, it has a sophisticated dynamic positioning system including thrusters and propellers, often computer controlled.  The drill ship has several advantages over fixed drilling rigs which sit on the seabed, in that it can rapidly move from one drill site to another and does not require extensive anchorage systems.

Diving support vessels

Divers are often needed for building and maintaining offshore structures and pipelines.  Specialised vessels to support divers have a moon pool, a pressurised chamber from which divers can descend, and which allows gradual decompression.  These vessels may also have sophisticated workshop facilities, closed circuit television for monitoring underwater structures, and facilities to carry out underwater welding work.  

Perhaps the most sophisticated of all oil industry support craft are the manned or unmanned submersibles to allow inspection or maintenance of underwater structures at depths beyond which divers can work.  With hulls designed to withstand high pressures, and sophisticated control equipment, they owe a lot to military submarine technology.

Surviving offshore: oil rig support
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