NC starts work on Statfjord C GBS

By Trude Meland, Norwegian Petroleum Museum

Norwegian Contractors (NC) began work on building the concrete gravity base structure (GBS) for Statfjord C on 10 November 1980, before the contract had officially been signed. The sheet pile retaining wall was re-established to be ready by 1 December, and notifications issued to shipping in the Gands Fjord. NC took the chance of starting up on its own account in order to provide work for personnel it wanted to retain.

— Casting of the Statfjord C GBS. Photo: Norwegian Contractors/Norwegian Petroleum Museum

Slip casting the Statfjord C GBS (concrete base structure). PhOTO: NORWEGIAN CONTRACTORS/NORwegian Petroleum Museum

This contract was the first awarded for the Statfjord C construction project, and covered a four-shaft GBS. The structure was virtually identical to Statfjord B, with 20 oil storage cells forming its bottom section. Each cell had an internal diameter of 23 metres and could store 260 000 tonnes of crude.

NC needed 200 additional permanent employees, and 1 500 people would be working at the Hinnavågen facility during the most hectic phase when the shafts were slipformed. Schoolchildren and students once again had the chance to earn a few thousand kroner during the four weeks that this operation would take.

Installation of the steel skirts to ensure that the platform stood stably on the field started during January. This initial period presented the biggest challenges.

NC’s design personnel only had a short time to do their work before construction began in the dock. Bottom conditions at the Statfjord B and C sites were completely different, and a new base structure was required.

The computers used to calculate pressure, stress and other key conditions lacked the capacity that such machines now possess. It took them 12.5 days to conduct the global analysis – the most extensive of the lot – covering stresses in the concrete.

Physical work in the dry dock could begin on 12 January 1981. Three years later, on 18 January 1984, after a three-day delay because of bad weather, the concrete structure could leave the Gands Fjord off Stavanger for Vats and mating with the topside. [REMOVE]Fotnote: Norsk Oljerevy , no 12, 1983. “Statfjord C – 800 000 tonn stål og betong”.

To learn more, see: Building Statfjord C