West Navion, a Dynamically Positioned Drill Ship

which can maintain position whilst drilling (when

not drilling It can also move from one location to

another easily). The picture on the left shows the

upper works of a RamRig drilling derrick. The

Rams either side of the dilling station have a long

stroke and can move with consistant force from

end to end of stroke. It also has a system for

heave compensation which againg accomodates

the small heave movements of the ship whilst

maintaing a consistant drilling rate. Finally West

Odin had two such rigs interconnected. This

allows a hole to be drilled by one drill station whilst

the other station is making up dounle lengths of

pipe. Muck of the pipe handling and drilling is

automatically controlled to minimise manual

handling. This type of rig was the step change

around 2000, subsequently rigs have been made

more automatic and other derrick designs and Box

Girder style structures are used. The main

emphasise of this type of rig is that it was

constucted as a Module in one location ,

transported and lifted in in situ. Its foundations are

slightly different to other modules in that the loads

from drilling are large and transmitted into the

ships frame via haunches which spread the loads

into adjacent frames. West Navion had other

conventional modules for Power Generation which

were box like and similarlry lifted in by floating

Shear Legs.

The string of pictures below show some of the elements of the installation of various pieces of the drilling compensation system.