It is in 4400 feet of water, 125 miles of the Louisiana coast, in Green Canyon Block 654, in the Western Atwater Foldbelt trend. This is where BHP has made three other discoveries in recent years - Mad Dog, Atlantis and Neptune.
BHP said further appraisal drilling needed to be carried out before a reserves estimate could be put on the discovery. Shenzi lies nine miles northwest of the Atlantis discovery and 15 miles west of Neptune.
The size of Shenzi discovery can be far lower and still be a commercial proposition given its proximity to the other discoveries and the economics of clustered subsea field development.
BHP said it was planning to spend almost $4.4 billion on development of the earlier discoveries in the next few years.
The other partners are BP (28%) and Amerada Hess (28%).