The first steel-cutting ceremony was attended by Norway Petroleum and Energy Minister Kjell-Børge Freiberg.
Kværner received a contract from Equinor in February to deliver the topside modules for the FPSO vessel and integrate them with the hull.
Equinor technology, projects and drilling executive vice-president Anders Opedal said: “Johan Castberg is the next major development on the Norwegian continental shelf and will open a new area in the Barents Sea for Equinor.
“Johan Castberg’s development will have ripple effects equivalent to 47,000 man-years in Norway during the development phase. The value of Norwegian goods and services will amount to around Nkr25bn ($2.92bn).”
During the construction phase, the contract is expected to create 4,800 jobs.
Besides Stord, construction of the topside components will take place in Verdal, Egersund and Sandnessjøen over the next few years.
Upon completion, the topside will be installed on the 200m-long FPSO vessel.
The platform will be engaged in production on the Johan-Castberg field for 30 years. Production start-up is expected to take place in 2022.
Meanwhile, construction of the hull and the turret are respectively underway in Singapore and Dubai.
Equinor expects these components to arrive at the Stord yard in 2020 for assembly and completion.
The development cost of the field is estimated to be around Nkr49bn ($5.73bn).
The field development plan comprises an FPSO vessel and subsea development, including a total of 30 wells, ten subsea templates and two satellite structures.