Independence Hub, Gulf of Mexico, USA

The Independence Hub is the result of five independent exploration and production companies and a midstream energy company coming together to facilitate the development of multiple ultra-deepwater natural gas and condensate discoveries in the previously untapped Eastern Gulf of Mexico. It is an affiliate of Enterprise and the Atwater Valley Producers Group, which includes Anadarko, Dominion, Kerr-McGee, Spinnaker and Devon Energy.

The development will be based on six natural gas anchor fields in the Atwater Valley, DeSoto Canyon and Lloyd Ridge areas of the deepwater Gulf of Mexico. The fields' water depths range from 7,800ft to 9,000ft.

ATWATER VALLEY, DESOTO CANYON, LLOYD RIDGE

Atlas / Atlas NW (Lloyd Ridge blocks 5/49/50): Anadarko (100%) encountered 180ft of gross pay in nearly 9,000ft of water in June 2003. Atlas was followed by a satellite discovery, Atlas NW, in January 2004.

Jubilee (Atwater Valley blocks 305/349 and Lloyd Ridge blocks 265/309): Anadarko (100%) discovered the Jubilee field in April 2003 in 8,800ft of water. The discovery well encountered 83ft of net pay and was drilled to the target depth of 18,310ft.

Merganser (Atwater Valley blocks 36/37): Kerr-McGee (50%) discovered Merganser in 2001 approximately 180 miles south of Mobile in a water depth of 7,900ft. Four high-quality Miocene reservoirs were penetrated and each has excellent flow characteristics. Devon Energy holds the remaining 50%.

San Jacinto (DeSoto Canyon blocks 618/619): Dominion announced the San Jacinto natural gas discovery in April 2004, approximately 140 miles south of Mobile Bay. Dominion (53%) is the operator on behalf of Spinnaker (27%) and Kerr-McGee (20%). The discovery well was drilled to a total measured depth of 15,829ft and encountered approximately 100ft of net pay in multiple reservoir sands. This was followed by an appraisal well encountering 100ft of net pay in the same multiple reservoir sands. The field will be developed jointly with the Spiderman discovery.

Spiderman (DeSoto Canyon blocks 620/621): The Spiderman field was discovered in November 2003. It was drilled in 8,100ft of water to a total depth of 18,065ft and encountered more than 140ft of net pay. Anadarko (45%) operates the field on behalf of Dominion (36.67%) and Spinnaker (18.33%)

Vortex (Atwater Valley blocks 217/261 and Lloyd Ridge blocks 177/221): Vortex - Anadark(50%) and Kerr-McGee (50%) - was discovered in December 2002, and is located in a water depth of 8,344ft. The exploration well penetrated approximately 75ft of high-quality pay in a Miocene-age reservoir.

INDEPENDENCE HUB PLATFORM

The fields will be tied-back to the platform through producer-owned subsea flowline systems. Enterprise will design, construct, install and own Independence Hub, a deep-draft, semi-submersible platform with a two-level production deck, which will be capable of processing 4,250b/d of condensate and 950MMft³/d of gas. There are 12 10in risers and four 8in risers as well as 12 control umbillicals. Gas is exported by a 20in riser.

The semisubmersible has a payload of 19,300t and displacement of 46,160t. It is moored in a 12-leg mooring system with 9in rope. The hull measures 232ft square and 160ft in height. The hull columns measure 46ft square and the pontoons are 36ft by 26ft. The draft is 105ft. The topsides weight 10,250t and measure 140ft by 220ft by 35ft. There is accommodation for 16 people.

The platform, which is estimated to cost $385 million, will be operated by Anadarko. It has excess payload capacity to tie-back up to ten additional fields. Independence Hub will be located on Mississippi Canyon block 920, in a water depth of 8,000ft.

Enterprise will own, install and operate 140 miles of 24in pipeline with a capacity of approximately 850MMft³/d of gas. Named Independence Trail, the pipeline, which is estimated to cost $280 million, will redeliver the production from Independence Hub into the Tennessee Gas Pipeline located in West Delta 68. First production is expected in 2007.

DEVELOPMENT CONTRACTS

Enterprise has awarded key contracts to:

• Atlantia Offshore Limited for hull and mooring systems design, fabrication, construction and dry transportation to the staging site at Ingleside, Texas
• Heerema Marine Contractors for hull and mooring systems transport and installation
• Alliance Engineering for topsides engineering
• Kiewit Offshore Services for topsides fabrication and installation onto the hull
• Allseas USA, Inc. for installation of the gas pipeline
• Marlow Ropes for mooring lines

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