The oil giant successful drilled an appraisal well in a previously untested northern segment of the Mad Dog field.

BP plc (LON:BP) announced today the drilling of a successful appraisal well in a previously untested northern segment of the Mad Dog field in the US Gulf of Mexico.

The well results confirm a significant resource extension for the Mad Dog Field complex, which includes the existing field, in production since 2005, and appraisal drilling of the Mad Dog South field in 2008 and 2009.

Pending confirmation through future appraisal drilling, the total hydrocarbons initially in place in the Mad Dog field complex are now estimated to be up to four billion barrels of oil equivalent.

The well, drilled by BHP Billiton on behalf of the unit operator BP, is located on Gulf of Mexico Green Canyon block 738 approximately 140 miles (225 kilometres) south of Grand Isle, LA., in about 4,500 feet (1,371 metres) of water.

The well encountered about 166 net feet (50 metres) of hydrocarbons in the objective Miocene hydrocarbon-bearing sands and discovered an oil column of more than 300 feet (91 metres).

Bob Dudley, BP group chief executive: "With these additional hydrocarbon resources north of the main field, Mad Dog has been firmly established as a giant field in BP's Gulf of Mexico portfolio, rivalling Thunder Horse in size of resource."

BP maintains a 60.5 per cent working interest in Mad Dog. BHP Billiton has a 23.9 per cent interest, Chevron Corporation, through its subsidiary Union Oil Company of California, has a 15.6 per cent interest.