Project Profile
Value: US$1,200 million
Location: Gulf of Mexico in Atwater blocks 573, 574, 575, 617, and 618, approximately
120 miles from the coast of Louisiana, USA
Reserves: 100 and 150 million barrels of oil equivalent
Water depth: from 4,200ft to 6,500ft
Start-up Year: July 2008
The Neptune field is located in the Gulf of Mexico in Atwater blocks 573, 574, 575, 617, and 618, approximately 120 miles from the coast of Louisiana. The water depths range from 4,200ft to 6,500ft. Recoverable reserves at the Neptune field are estimated to range between 100 and 150 million barrels of oil equivalent. BHP Billiton is designated operator with a 35% share, partners being Marathon Oil (30%), Woodside Energy (20%) and Repsol subsidiary Maxus Exploration (15%). Neptune was discovered in 1995 and marked the first discovery in the Western Atwater Foldbelt. An initial appraisal well (Neptune-2) was drilled in 1997. BHP Billiton took over operatorship in 2002. In order to delineate the field, the operator subsequently drilled four more appraisal wells, with two sidetracks. In 2004 BHP Billiton signed a two-year contract with the drilling contractor GlobalSantaFe for the use of this rig in the GoM. Production was due to have started by the end of December 2008 but was first deferred to the first quarter. Then, in March 2008, BHP Billiton, during a routine inspection immediately prior to start-up of the TLP, discovered \'structural anomalies\' in its hull, delaying start-up further. Production finally began in July 2008. Gross costs for the development were originally estimated at approximately US$850m but the total cost is now widely reported to be US$1.2bn.
Neptune facility:
The Neptune facility has a design capacity to produce up to 50,000 barrels of oil and 50 million cubic feet of gas a day. Produced water is estimated at 30,000 barrels a day. There are permanent quarters for 26 people and temporary quarters for a further 24. The helideck is able to accommodate an S-92 helicopter. The design has three deck levels. There are three pontoons and it is linked to the seabed by six tendons (three by two). The tendon segments are in lengths of 289ft (88m) and were supplied by Europipe. The design of the hull and topsides was carried out by SBM Atlantia, which procured and project managed the project. The topsides were fabricated by Gulf Island fabricators in Houma, Louisiana while the hull was manufactured by Signal International in Orange, Texas. They were assembled by Heerema Marine Contractors, which also installed the tendons and the platform using the Thialf. The oil and gas is exported by the Caesar and Cleopatra trunk lines, in which BHP Billiton holds a 25% and 22% interest respectively. The new laterals were installed, and are owned and operated by Enbridge Offshore (Gas Gathering) LLC.
Operators:
BHP Billiton: Operator with 35% interest (since 2002)
Marathon Oil: 30% interest
W&T Offshore: 20% interest
Repsol subsidiary Maxus Exploration: 15% interest
Contractors:
GlobalSantaFe: Drilling contractor
Europipe: Supply of tendon segments
SBM Atlantia: Design of the hull and topsides
Gulf Island: Fabrication of topsides
Signal International: Manufacture of the hull
Heerema Marine Contractors: Installation of the tendons and the platform
Enbridge Offshore (Gas Gathering) LLC: Installation of the new laterals for the Caesar and Cleopatra trunk lines