Leaks in Statfjord A

By Trude Meland, Norwegian Petroleum Museum

Cracks in the concrete gravity base structure (GBS) for Statfjord A were discovered in 1976 during maximum submersion as part of the operation to mate with the topside. This damage had arisen as a result of excessive temperature fluctuations and a weak section in the concrete, and took two months to repair.

— “Twenty buckets a minute. The leak in Statfjord A will be sealed today”. Headline in Stavanger Aftenblad, 14 September 1976.

It transpired that there were two cracks, each 20 centimetres long, in the concrete between one “star” cell and a storage cell.[REMOVE]

Fotnote: Hanisch, Tore Jørgen og Nerheim, Gunnar; Norsk oljehistorie. Fra vantro til overmot? 1992, p. 392.

The GBS was taking in 15 000 litres of water per hour or 20 buckets a minute.[REMOVE]Fotnote: Stavanger Aftenblad. 14 September 1976. 20 bøtter i minuttet.

But the structure was never in any danger of tipping over or sinking. The pumps installed in the GBS were capable of discharging 1.2 million litres per hour, and had no problem controlling the water intrusion. Without the pumps, the GBS would have sunk 60-70 centimetres per day because of the extra displacement caused by the water.[REMOVE]Fotnote: Hanisch. op.cit. p 392

People from Aker Offshore Contractors (AOC) and Norwegian Contractors (NC) devoted the weekend to identifying what had happened. When the cracks were located, NC – the company responsible for the concrete structure – injected them with epoxy, a special and elastic form of concrete.

Sealing the cracks was a big job, and the incident led to delays. Installing such modules as the living quarters and the helideck had to be postponed until the damage was repaired.

To learn more, see: Building the Statfjord A topside at Stord Verft.