sentences:  The Schiehallion field, together with Foinaven, Clair, Lancaster and Solan fields, forms the frontier area generally termed as the "West of Shetland".Schiehallion field was discovered in 1993 by the semi-submersible drilling vessel "Ocean Alliance" while drilling the third exploration well in block 204 (well 204-3).The field is located in blocks 204/20 and 204/25 of the United Kingdom Continental Shelf in a water depth of .