25/2-18 S (Langfjellet) is a discovery in the central North Sea, 20 kilometres east of the Frigg field. The water depth is 120 metres. The discovery was proven in 2016. The reservoir contains oil and gas in Middle Jurassic sandstone in the Hugin Formation, at a depth of 3,500 metres. The plan is to develop Langfjellet as part of the Yggdrasil development (formerly NOAKA), together with other discoveries and abandoned fields in the area between the Oseberg and Alvheim fields. In December 2022, three plans for development and operation (PDO) were submitted for the Yggdrasil development, including the projects Hugin, Fulla and Munin. The PDO for Hugin includes the development of Langfjellet as a subsea tie-back to a new process platform, Hugin A, located at Frigg-GammaDelta in the southern part of the Yggdrasil area.
