The Independence Hub is located on Mississippi Canyon block 920 in a water depth of 8,000ft. It 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. The group is an affiliate of Enterprise and the Atwater Valley Producers Group, which includes Anadarko, Dominion, Kerr-McGee, Spinnaker and Devon Energy.
The development is 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. First production from the platform occurred in July 2007. By the end of 2007 the platform reached its design capacity of one billion cubic feet of gas per day.
In March 2010 one Mondo field well was completed and another is planned towards the end of 2010. The new wells will be connected to the platform in 2011.
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%.
Independence Hub's new Mondo wells will be connected to the platform in 2011."
San Jacinto (DeSoto Canyon blocks 618 / 619): Dominion announced the San Jacinto natural gas discovery in April 2004. It lies 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 - Anadarko (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.
Mondo NW (Lloyd Ridge blocks 1 / 2): Anadarko (50%) discovered the field in December 2004. Murphy Exploration & Production Company owns the remaining 50% interest in the field. The field is located at a water depth of 8,412ft.
Q (Mississippi Canyon blocks 960 / 961 / 1004 / 1005): Q field was discovered in June 2005 and is operated by StatoilHydro, which has a 50% interest in the field. The remaining 50% is held by Eni. Q field is located at a water depth of 7,973ft.
Independence Hub platform
The Independence Hub fields are tied-back to the platform through producer-owned subsea flowline systems. The Independence Hub is owned by Enterprise, which designed, constructed and installed the platform in 2007.
"The Anadarko platform cost $385m."
The deep-draft, semi-submersible platform with a two-level production deck, is capable of processing 5,000bpd of condensate and one billion cubic feet of gas per day. There are 12 10in risers and four 8in risers, as well as 12 control umbilicals. Gas is exported by a 20in riser.
The semisubmersible has a payload of 13,800t and displacement of 45,860t. It is moored in a 12-leg mooring system with 9in rope. The hull measures 232ft square and 170ft in height. The hull columns measure 46ft² 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 Anadarko-operated platform was built at a cost of $385m. It has an excess payload capacity to tie-back up to ten additional fields.
Enterprise also installed 140 miles of 24in pipeline with a capacity of approximately 850ft³ per day of gas. Owned and operated by Enterprise, the pipeline is called Independence Trail. The pipeline redelivers the production from Independence Hub into the Tennessee Gas Pipeline, which is located in West Delta 68. The total cost of the pipeline was estimated at $280m.
Independence Hub contracts
Enterprise awarded key contracts to:
•Atlantia Offshore 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 for installation of the gas pipeline
•Marlow Ropes for mooring lines