The Marathon-operated West Brae Field straddles Blocks 16/06a and 16/07a in the UK Central North Sea approximately 140 miles (225 km) NE of Aberdeen. The field was discovered in 1975 with drilling of exploration well 16/07-2. The West Brae reservoirs consist of Eocene Balder Formation and Upper Sele Formation Sandstones that were deposited in NW-SE trending submarine channels across the area. Development of the field commenced in April 1997 with first oil being achieved in October the same year. The field has been developed using sub-sea tie-back to the Brae A platform, which lies 5.6 miles (9 km) SE of the sub-sea manifold. Recoverable reserves are estimated to be 60 MMBBLs, of which some 23 MMBBLs had been produced by 31 December 1999.