The field has the capacity to produce 100,000 barrels of oil (gross) and 60 million standard cubic feet of gas (gross) a day, according to BHP Billiton. BHP Billiton said production would increase over the year as additional wells were completed and brought online.

Last week the Angostura project in the West Indies produced first oil while Minerva in offshore Victoria was commissioned two days ago.

Mad Dog is located in about 4,300 feet of water in green canyon Block 782 about 200 miles south of New Orleans, Louisiana.

BHP Billiton holds a 23.9% working interest in the field, which is operated by its 60.5% owner BP. Unocal holds the remaining15.6% working interest.

BP and BHP are also partners in the larger Atlantis field in the Gulf which is due to start production in 2006.

Mad Dog is BHP Billiton's first producing well in the Gulf of Mexico's Atwater Foldbelt, where the group made its initial deepwater exploration investments in the mid-1990s, BHP Billiton's energy group president Philip Aiken said.

"Today the company holds interests in more than 450 blocks in the Gulf of Mexico, with an active exploration and appraisal program, as well as development of the Atlantis field, which is scheduled to come onstream in 2006," Aiken said.

“It is an exciting time for us as we move forward to progress development studies at Neptune and Shenzi and appraise our discoveries at Puma, Chinook and Cascade. The Gulf has now emerged as Petroleum’s third core business after Bass Strait /Eastern Australian gas and the Pacific Basin LNG / Western Australian oil and gas.”

The Mad Dog development consists of a truss spar, equipped with facilities for simultaneous production and drilling operations.

Oil from Mad Dog will be transported via the Caesar pipeline, in which BHP Billiton has a 25% equity share, to the Ship Shoal 332B platform, where it will interconnect with the Cameron Highway Oil Pipeline System (CHOPS).

Mad Dog gas will be exported via the Cleopatra pipeline, in which BHP Billiton has a 22% equity share, to the Ship Shoal 332A platform, where it will interconnect with Manta Ray Gathering System, and from there to the Nautilus Gas Transportation System into Louisiana.

Mad Dog was discovered by the joint venture in 1998. Construction of the spar components and topsides commenced during 2002 in Pori, Finland and Morgan City, Louisiana. The overall capital cost of the project is around US$ 1.5 billion (BHP Billiton share US$ 368 million).