Like a challenge? Try this. Undertake one of the largest offshore projects ever developed by independent exploration and production (E&P) companies with a floating platform in record water depth producing from record water depth subsea wells. Add two owners and five producer companies contributing production. Part of the way through the project, add three more fields to the mix and increase processing capacity nearly 18%. Toss in a significant political exposure to increase the pressure. Then complete the whole job, from discovery of the first field to first gas production, in 5 1/2 years.
That's the Independence Project.
"We are confident this project will set a great example of environmental responsibility, collaboration among multiple companies and speed to first gas production which all demonstrate the positive benefits of opening additional acreage for leasing. More leasing access is good for the country," said Jim Alsup, Eastern Gulf of Mexico Area Manager for Anadarko Petroleum Corp., the operator of Independence Hub.
Anadarko went to work immediately after leasing the DeSoto Canyon and Lloyd Ridge blocks at Minerals Management Service Sale 181 for the Eastern Gulf in December 2001. It discovered Jubilee in April 2003 in 8,800 ft (2,684 m) of water in Atwater Valley blocks 305 and 349. Atlas in Lloyd Ridge 50 followed in June the same year and will be combined with Atlas Northwest in Lloyd Ridge 5 to share a gathering line called the Eastern Corridor System. The Spiderman discovery, located in DeSoto Canyon 620 and 621, followed in November 2003 with partner Hydro Gulf of Mexico LLC (formerly Spinnaker Exploration Co.) and Dominion E&P.
Dominion E&P was close behind with San Jacinto in DeSoto Canyon 618 and 619 with partners Hydro Gulf of Mexico and Kerr-McGee Corp. In addition to its interest in San Jacinto, Kerr-McGee Corp. was successful with Merganser, which was the first discovery in the area in December 2001 with partner Devon Energy. Merganser is located in Atwater Valley 36 and 37 in the Central Gulf. Kerr-McGee also participated in Vortex in Atwater Valley 261 (current partner Anadarko).
The speed with which these operators and partners reacted to the opening of that segment of the Eastern Gulf of Mexico should send a message to Congress. The industry will produce significant amounts of oil and gas quickly when additional areas are opened for leasing, Alsup said.
Producers group
To get the production to market, the producers formed the Atwater Valley Producers Group, an informal collection of operators and partners with discoveries in the area.
Those discoveries and partnerships led to the Independence Hub concept, a central semisubmersible platform located in Mississippi Canyon 920 to produce all seven fields in a hub and spoke concept. The original concept called for a two-level production deck and hull with the capacity to handle 4,250 b/d of condensate, 850 MMcf/d of gas and 3,000 b/d of produced water.
The producers agreed to a commercial solution where Enterprise Products Partners LP would design, construct, install and own the Independence Hub while Anadarko operated the facility. Enterprise later sold a 20% ownership to Helix Energy Solutions Group, Inc. (formerly Cal Dive International). In addition to the hub, Enterprise agreed to design, install and own the 134-mile (216-km) gas export pipeline from the hub to a new-built shallow water platform in West Delta 68 that interconnects with Tennessee Gas Pipeline. The third-party ownership system worked well for Anadarko at its Marco Polo field, and the arrangement freed up money for exploration and development that the operators otherwise would have had to invest in platform and pipeline hardware. "We like the model," Alsup said.
Expansion
The majority of the deck space will be filled with gas processing and compression equipment, water treatment facilities, glycol reclamation, and accommodation quarters for 40 people. Since all fields will utilize subsea tie-backs to the hub, a drilling rig will not be installed.
This year, the group added Anadarko's Cheyenne and Mondo Northwest (with partner Murphy) discoveries along with Hydro Gulf of Mexico's Q discovery with Dominion E&P. The Cheyenne field, which was originally drilled to test a deep prospect, will set the subsea production water depth record at 8,950 ft (2,730 m). Shell's Coulomb field in Mississippi Canyon 657 holds the current water depth record at 7,555 ft (2,304 m).
The additional discoveries called for additional capacity; Enterprise/Helix and the producer group agreed to increase the gas processing and pipeline export capacity to 1 Bcf/d of gas. Primary modifications to the topsides included the addition of a compressor, heat exchanger and increased capacity for the condensate and firewater pumps; the hull remained relatively unchanged.
In total, Alsup estimated the capital investment of the project at about US $2.5 billion including the hub, pipeline, drilling, completions and subsea infrastructure.
Collaboration
Following several months of evaluating more than 40 infrastructure scenarios, the producers agreed on how they would develop the complex. This early alignment allowed the project to proceed without significant delays.
The plan called for three separate, record-setting facilities projects; subsea infrastructure design and installation; the processing hub design, fabrication, and installation; and the gas export pipeline design and installation. The subsea gathering complex reaches some 60 miles (97 km) from Spiderman in the north to Cheyenne at the south end and 30 miles (48 km) wide from Merganser to Atlas. The arrangement required a high level of communication among the multitude of project teams, companies and contractors. One of the key components to collaboration on the project is the formation and use of integrated project teams, allowing the companies to maintain continuous alignment. Enterprise leads the team for the hub, but all of the producing companies have representatives on it.
The coordination effort extends well beyond the producers and Enterprise/Helix. Alliance Engineering was contracted to perform the topsides engineering, Atlantia Offshore Ltd. is responsible for the hull and mooring design, fabrication and transportation. Heerema Marine Contractors will install the polyester/chain mooring system and several of the flow lines, Kiewit Offshore Services is nearly finished with the topsides fabrication and assembly, AllSeas is installing the gas export pipeline and several of the larger flowlines and risers, and Subsea 7 is installing the umbilicals.
Some of the collaborative components were easier than others. Most of the technology and equipment was an extension of existing hardware, Alsup said. For example, the subsea trees all were certified for operation in 10,000 ft (3,050 m) of water. "The engineering companies and equipment providers had done most of the engineering and certification to assure the equipment would work in these water depths," he said. For the most part, the partners all are using the same equipment for development to minimize maintenance and inventory. The different operators agreed on essentially the same subsea trees, wet gas flow meters, subsea manifolds and other equipment. The larger purchase orders and installation contracts worked to the group's favor due to economies of scale. Other parts of the job were more difficult.
Challenges
The biggest challenge involved steel catenary risers and umbilicals hanging nearly 2 miles (3.2 km) off the platform to the sea floor. Stresses on these elements due to wave motion, floating platform motions and vortex-induced vibration had to be addressed.
The group increased the expected design life of the risers with a combination of strakes and fairings to offset vortex-induced vibration. To increase the tensile strength of umbilicals, Kvaerner is installing carbon fiber rods - this pioneering work will likely be used on future ultradeepwater projects.
Still another challenge was finding contractors capable of working at these depths, Alsup said. Heerema and AllSeas had to be booked well in advance of the actual installation project, and AllSeas upgraded its Solitaire pipelay vessel to ensure the requirements of the job could be met. It extended the pipelay stinger on the back of the vessel, increased tension capacity two-fold and increased the buoyancy of the ship.
The Atwater Valley Producers Group paid particular attention to the flow assurance capabilities on the platform. To prevent methane hydrate formation in the flow lines, they chose to inject monoethylene glycol (MEG). As gas flows from the wells to the platform, the process equipment recovers and regenerates the MEG for use again. "We will have the largest offshore MEG reclamation unit in the world. It's 40% bigger than any existing offshore unit," Alsup said.
In a lease-like commercial arrangement, the producers pay for processing capacity in relation to their use of the platform. "Anadarko reserved 49% of the gas processing capacity for the first 5 years," he said. After the expansion to 1 Bcf/d of gas, the companies will not reallocate firm capacity for the first 5 years of operations.
The deepwaterGulf of Mexico is an important part of Anadarko's production growth, Alsup said. The company is committed to a leadership role in the deepwater frontier. Part of Anadarko's early pioneering work offshore was in its interpretation of subsalt reservoirs and subsequent discoveries at Mahogany, Tanzanite and Hickory. It extended that experience in tandem with Enterprise and Helix with the Marco Polo platform, which held the record for the deepest water tension-leg platform in the world at the time of installation in 2004.
Model
The model of multiple operators contributing to a central hub which is owned by a third party "absolutely" works in the Gulf of Mexico, he said. Whether that same model would work in other countries would depend on the terms agreed upon with the host governments, he added, but the aggregation and production of reserves through a hub-and-spoke design should work well anywhere in the world.
Asked about lessons learned in the project, Alsup said the group has learned a lot. The involvement of all of the parties in reaching early alignment was critical to the success of the project. The group learned many technical lessons along the way, he added, but collaboration among the integrated project teams meant they didn't have to learn those lessons the hard way. Each of the producers and Enterprise have their own deepwater experience that they bring to the project, leveraging the combined experience of all the parties.
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