The Gullfaks C mating

Av Ole Jone Eide

On 27 February 1989, the Gullfaks C topside was mated to the substructure.

— Digernessundet, 27 February 1989: The steel deck is being moved over the concrete substructure. Photo: Øyvind Hagen/Equinor.

At the turn of the year 1988/89, the topside and the substructure (also called GBS, or Gravity-Based Structure) of Gullfaks C were located a few kilometres apart, at Aker Stord’s yard in Leirvik and in the Digernessundet sound a little farther south, respectively.

Norwegian Contractors won the contract to load the topside onto barges and transport them to Digernessundet for mating with the substructure. The contract was worth nearly NOK 100 million.[REMOVE]Fotnote: Norsk oljerevy / Norwegian Oil Review. 1987, Vol. 13, No. 9, p. 51. Aker Stord was tasked with connecting the main interfaces of the topside to the concrete structure in Digernessundet. Because of bad weather, the tow only started after several postponements, which cost Statoil [now Equinor] NOK 10 million.[REMOVE]Fotnote: Status (1989), No. 4, p. 12. “The storm costs millions.

Between 2 and 3 a.m. on February 27, the tow of the topside began. During the day, work started to mate the topside to the substructure. In total, 355 bolts were to fasten the two together. This demanded high accuracy in fine-tuning the positioning of the topside relative to the substructure. At 6 p.m., the two parts made contact for the first time. Late in the evening, around 10 percent of the topside weight had been transferred to the concrete structure.

The deck on its way over the shaft, seen from underneath Photo: Rolf C T Nielsen/Norwegian Petroleum Museum

Early on the morning of March 1, the full topside weight rested on the substructure. On March 3, the platform had been raised so the topside stood 56 meters above sea level, and the next day the first Statoil [now Equinor] representatives came aboard.

Aker Stord had a seven-week window (four weeks less than originally planned) to finish preparations before tow-out to the field. Project manager Torleif Gram at Aker Stord therefore looked ahead to a very busy period, noting that the limited weeks remaining had to be used to the fullest, requiring good planning and follow-up.[REMOVE]Fotnote: For more information of the mating operation, see several shorter articles by Tor Resser et al. In: Sunnhordland, 28 February 1989, pp. 1 and 10. (The quotation is taken from p. 10 under the headline “Busy Days at Aker Stord.”)