Equinor grows Johan Castberg resource base with Polynya Tubåen oil discovery

Equinor and its partners have discovered another oil accumulation within tieback range of the Johan Castberg field infrastructure in the Barents Sea.

The semisub COSL Prospector drilled well 7220/7-5 on the Polynya Tubåen prospect in 361 m of water, 16 km southwest of the original Johan Castberg discovery well and 210 km northwest of the port of Hammerfest.

Early analysis indicates 14-14 MMboe recoverable.

The well 7220/7-5 encountered a 26-m gas column and a 26-m oil column in the Tubåen Formation in reservoir rocks totalling 39 m, the Norwegian Offshore Directorate reported, with good reservoir quality.

Grete Birgitte Haaland, Equinor’s area director for Exploration and Production North, said: “We plan to drill one to two exploration wells annually in this region going forward to increase the resource base and maintain plateau production for a longer period [from Johan Castberg].”

Equinor originally estimated Castberg’s recoverable volumes at 500–700 MMbbl. It now aims to increase this range by an additional 200–500 MMbbl.

In June 2025, the partners discovered 13-20 MMbbl of oil with a well on the Drivis Tubåen prospect.

Construction recently started for Isflak, the first discovery to be tied into Johan Castberg since production started on March 31 last year. Aker Solutions is building a well frame in Sandnessjøen for the two new wells that will be connected to existing subsea facilities.

The Johan Castberg field and its FPSO are 220 km northwest of Hammerfest. The partners are Equinor Energy (operator) 46.3%, Vår Energi 30%, and Petoro 23.7%.