Argus North Sea Dated (Crude) The North Sea crude market is one of the most important crude markets in the world. The Argus North Sea Dated price is derived from a methodology which involves four crude grades, Brent, Forties, Oseberg and Ekofisk (BFOE). This index is the market's implied value for the North Sea Dated price reference obtained by cross referencing forward trade, Contracts For Difference trade and physical differentials for the four BFOE crudes within the 10 days - month ahead assessment period.