The Independence Hub was a producing gas and condensate hub located at Mississippi Canyon block 920, at a water depth of 8,000ft. It was decommissioned in 2019.
The hub was the result of Atwater Valley Producers Group and Enterprise Products Partners, 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.
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The Atwater Valley Producers Group included five independent exploration and production companies, namely Anadarko, Dominion, Kerr-McGee, Spinnaker, and Devon Energy.
The development was 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 ranged between 7,800ft and 9,000ft. First production from the platform occurred in July 2007. The platform reached its design capacity of one billion cubic feet of gas per day by the end of 2007.
The Independence Hub platform ceased production in December 2015, after more than eight years of production and extraction of approximately 1.3 trillion cubic feet of gas.
Independence wells
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. Atlas / Atlas NW were discovered in Lloyd Ridge blocks 5 / 49 / 50.
The company discovered the Jubilee field at a water depth of 8,800ft within Atwater Valley blocks 305 / 349 and Lloyd Ridge blocks 265 / 309 in April 2003. The discovery well encountered 83ft of net pay and was drilled to the target depth of 18,310ft.
Kerr-McGee discovered Merganser within Atwater Valley blocks 36/37 in 2001, approximately 180 miles (289.68km) south of Mobile at a water depth of 7,900ft. Four high-quality Miocene reservoirs were penetrated and each had excellent flow characteristics. Kerr-McGee and its partner Devon Energy owned the field on a 50:50 basis.
Dominion announced the San Jacinto natural gas discovery in DeSoto Canyon blocks 618 / 619 in April 2004. The discovery was situated approximately 140 miles (225km) south of Mobile Bay. Dominion (53%) was 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. It was followed by an appraisal well encountering 100ft of net pay in the same multiple reservoir sands.
The Spiderman field was discovered within DeSoto Canyon blocks 620 / 621 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%) operated the field on behalf of Dominion (36.67%) and Spinnaker (18.33%).
Vortex, which was owned by Anadarko (50%) and Kerr-McGee (50%), was discovered within Atwater Valley blocks 217 / 261 and Lloyd Ridge blocks 177 / 221 in December 2002 and was located at a water depth of 8,344ft. The exploration well penetrated approximately 75ft of high-quality pay in a Miocene-age reservoir.
Anadarko discovered the Mondo NW field within Lloyd Ridge blocks 1/2 in December 2004. It held 50% interest in the field, while Murphy Exploration & Production Company owned the remaining 50% interest in the field. The field was located at a water depth of 8,412ft.
Q field was discovered at a water depth of 7,973ft within Mississippi Canyon blocks 960 / 961 / 1004 / 1005 in June 2005. It was operated by StatoilHydro, which is now known as Equinor, with a 50% interest in the field. The remaining 50% was held by Eni.
Independence Hub platform details
The Independence Hub fields were tied back to the platform through producer-owned subsea flowline systems.
The deep-draft, semi-submersible platform with a two-level production deck, was capable of processing 5,000bpd of condensate and one billion cubic feet of gas per day. There were 12 10in risers and four 8in risers, as well as 12 control umbilicals. Gas was exported by a 20in riser.
The semisubmersible had a payload of 13,800t and displacement of 45,860t. It was moored by a 12-leg mooring system with a 9in rope. The hull had a length of 232ft and a height of 170ft. The topsides weighed 10,250t and measured 140ft by 220ft by 35ft. The platform was designed to accommodate 16 people.
Built at a cost of $385m, the Anadarko-operated platform has an excess payload capacity to tie back up to ten additional fields.
Enterprise also installed 140 miles (225km) of 24in-diameter pipeline with a capacity of approximately 850ft³ per day of gas. Owned and operated by Enterprise, the pipeline is called Independence Trail. The pipeline redelivered the production from Independence Hub into the Tennessee Gas Pipeline, located in West Delta 68. The total cost of the pipeline was estimated at $280m.
Contracts involved
Atlantia Offshore was awarded the contract for hull and mooring systems design, fabrication, construction and dry transportation to the staging site at Ingleside, Texas.
Heerema Marine Contractors were contracted for hull and mooring systems transport and installation.
Alliance Engineering provided the topsides engineering while an offshore and underwater facilities contractor Kiewit Offshore Services was engaged for topsides fabrication and installation onto the hull.
Allseas USA, an offshore pipelay and subsea construction company, was awarded the contract for the installation of the gas pipeline.
The mooring lines were supplied by Marlow Ropes, a synthetic fibre ropes manufacturer.
US-based life-of-field mooring solutions provider InterMoor executed the project management and engineering work for the decommissioning of five umbilicals from the Independent Hub platform. The umbilicals were decommissioned using Joshua Chouest, an anchor handling vessel (AHV).
