The platform is located around 185 kilometres west of Haugesund, where sea depth is 127 metres.
The field was discovered by Hydro in 1991, and came on stream on 23 September 2003.
Grane is the first field on the Norwegian continental shelf to produce heavy crude oil. This oil differs from other types in that it is found in younger geological formations than what is usual on the continental shelf, namely in sandstone from the Tertiary period, deposited around 60 million years ago.
The oil is transported by pipeline to the Sture terminal, where it is stored in large rock caverns in the mountainside prior to shipment to the world market.
When the Grane field came on stream, its recoverable reserves were estimated to total 700 million barrels of oil.
The Grane oil is transported through a 212 kilometre long pipeline to Equinor's Sture terminal in Øygarden, west of Bergen.