15/12-21 (Grevling) is a discovery in the central part of the North Sea, 15 kilometres south of the Sleipner Øst field. The water depth is 90 metres. Grevling was proven in 2009, and delineated by wells 15/12-21 A, 15/12-23 and 15/12-23 A. The discovery is situated above a large salt structure. The reservoir contains oil in sandstone of Late Triassic to Middle Jurassic age in the Skagerrak, Bryne, Sleipner and Hugin Formations. Various options are being evaluated for a combined development with the adjacent 15/12-18 S (Storskrymten) discovery. The plan for development and operation (PDO) is expected to be submitted by the end of 2022.