Gullfaks B: from steel to concrete
The feasibility report for Gullfaks Phase I was submitted to the authorities on November 20, 1980. In it, the license group reviewed several possible development solutions for block 34/10.
On June 10, 1981, the Norwegian Parliament approved a phased development of the field, where the construction of two platforms in the western part of the reservoir would constitute Phase I. The government approved the plan on October 9 that same year.
Plans for Gullfaks A were already relatively concrete when the field development was approved in 1981. It was to be an integrated living, production, and drilling platform with a concrete substructure. The concept for Gullfaks B, however, was still taking shape.
In Statoil’s 1981 annual report, Gullfaks B was mentioned in just one sentence. It was described as a combined drilling and accommodation platform, scheduled to begin operations in 1989.[REMOVE]Fotnote: Det norske stats oljeselskap a.s. (1981). Årsberetning og regnskap 1981 (s. 7). As for the substructure, nothing was set in stone—or concrete.
From steel to concrete
In 1980, planning for Gullfaks B was based on a preliminary assumption that it would be a steel platform. Since Gullfaks B was intended to send production to Gullfaks A, it did not require its own processing facilities. This reduced the weight the substructure needed to support, making a steel structure a viable option.
However, concrete eventually became the preferred construction material. This shift was partly due to the realization that the required amount of steel was greater than initially estimated. Other factors included Statoil’s growing familiarity with concrete, which had been used for all the Statfjord platforms. Additionally, a concrete substructure would increase storage capacity at the field.[REMOVE]Fotnote: Hatlestad. H, Femti år med oljeproduksjon: min historie (2021). s. 39
By 1982, Statoil’s annual report confirmed that the B platform would be built with a concrete support structure. “[REMOVE]Fotnote: Det norske stats oljeselskap a.s. (1982). Årsberetning og regnskap 1982 (s. 10).
By early 1983, it was decided that Gullfaks B would also be built as a concrete platform. However, several different substructure designs were still under consideration.
Designing the concrete substructure
Statoil received two bids for the construction of the Gullfaks B substructure. One came from the French Doris Group, which had designed the Ekofisk tank, while the other came from Norwegian Contractors (NC). Both proposals featured a three-shaft deck support structure.
However, the designs for the base structure were quite different. The Doris Group proposed four large storage cells, one at each corner of a square foundation. NC’s design resembled the substructure used for previous Condeep platforms.
The contract for building the substructure was awarded to NC. Statoil justified the decision by stating that NC had offered a significantly lower price. Both concepts were considered feasible and functional.
Construction began in March 1985 in Hinnavågen and Gandsfjorden, following the same process as the Gullfaks A substructure. The contract was valued at NOK 940 million (1983 value) and included pre-engineering of the mechanical equipment for the concrete structure.[REMOVE]Fotnote: Status: internavis for Statoil-ansatte. (1983). Nr. 17, s. 2.