The Exact Positioning of Oseberg 'A' Platform

This paper describes the planning and execution of the exact positioning of the 800,000 tonne Oseberg A production platform.

Oseberg A is the tenth Condeep concrete platform to have been designed, constructed and installed in the North Sea by Norwegian Contractors, and of all the Condeep structures installed to date, none have been positioned with the same degree of accuracy as this one.

As have all Condeep platforms, Oseberg A was constructed to near 100% completion inshore, in sheltered waters, on the west coast of Norway. And then finally, in June 1988, the floating structure was towed to the Oseberg field in the North Sea where the platform was positioned and installed on site in 109 metres of water.

Whereas previous positioning of such giant structures had been carried out through the utilization of free running tugs in combination with dowels, a new method of positioning had to be developed for the Oseberg A allowing for much more precision. Compared with the generous installation tolerances of the past, that had always been met with ample margins, the absolute requirements in regard to the exact positioning of Oseberg A on the field represented quite a marine engineering and operation challenge. This paper describes how that challenge was met, and how the platform was successfully positioned less than 0.1 meter (4 inches) from theoretical centre.