process for converting an existing semi-submersible platform.

摘要

A method for converting a semi-submersible drilling or accommodation rig into a dynamically positioned vessel in which the rig has pontoon bodies submergible below a surface of a body of water for producing displacement, support columns extending upright from the pontoon bodies and oriented for intersecting the surface of the body of water to define a waterline area for the rig, and a work deck supported on the support columns and arranged to be disposed at a position above the surface of the body of water. The conversion method includes prefabricating a rig extension in which the rig extension has a pontoon body extension, a work deck extension and a supplemental support structure connecting the work deck extension to the pontoon body extension. The rig extension is then connected to the semi-submersible rig at locations proximate one of the pontoon bodies and at the work deck. Thruster(s) may be optionally added at the pontoon body extension. The conversion is utilized to increase the water displacement of the rig to produce a water displacement of the converted vessel greater than the water displacement of the rig and to provide the converted vessel with a water line area greater than a water line area of the rig thereby increasing a deck-load capacity and stability of the converted vessel. Supplemental power generating and distribution equipment is installed which includes at least one diesel generator in the rig extension. The thruster is at least primarily powered by the supplemental power generating and distribution equipment.