Two for one

Audrey Leon

August 1, 2015

When developing the Lucius and Heidelberg fields in the deepwater Gulf of Mexico, Anadarko Petroleum opted for a “design one, build two” strategy. Audrey Leon reports on how the Lucius field, which began production in January, came to be.

Anadarko’s Lucius truss spar when it came onstream in January 2015.
Photo from Robert Seale/Anadarko Petroleum.

In January, Anadarko Petroleum brought its Lucius field online using a truss spar design. The Lucius development is the first created via the US independent’s “design one, build two” strategy. A second spar, Heidelberg, left Corpus Christi, Texas, in late June and has been upended at its namesake field. It is now swiftly moving toward first production, due by April 2016.

The Lucius field is approximately 275mi southeast of Galveston, Texas, and includes portions of Keathley Canyon blocks 874, 875, 918 and 919 in the deepwater Gulf of Mexico, in about 7000ft water depth. The first exploration well, drilled in 2009, encountered roughly 200ft of net pay in subsalt Pliocene and Miocene sands. The find was described as a three-way structure against salt with indications of thick reservoir sands with very good porosity and permeability.

Anadarko operates Lucius with 23.8% interest. Its partners are Freeport-McMoran (25.1%), ExxonMobil (23.3%), Petrobras (11.5%), Eni (8.5%), and Inpex (7.75%).

At the time the discovery was announced, Anadarko had considered utilizing its recently decommissioned Red Hawk spar (OE: May 2015) to produce the Lucius field. Instead, the independent chose to construct a new standalone facility. A tension leg platform was dismissed as a possibility due to the water depth as well as the current technical and cost limitations on tendons, Anadarko’s Lucius Project Manager Matthew Lamey and his co-authors said in OTC paper 25868-MS, presented at this year’s OTC in Houston. Additionally, other considerations included the need to avoid landing the umbilicals and steel catenary risers (SCRs) in less desirable areas with slopes, indicating less stable surfaces.

Ultimately, Anadarko went with a truss spar given its previous experience with the technology on its Boomvang, Nansen, Gunnison, and Constitution developments.

“A truss spar was chosen because it could utilize three groups of mooring lines, while four group of moorings lines associated with a semisubmersible would have been difficult to implement given the geotechnical challenges identified on the site,” Lamey et al. wrote. The mooring system consists of nine legs, grouped 3x3. The chain mooring lines are secured to the seabed with suction piles.

Additionally, the truss spar for this wet tree-only development was selected to mitigate site terrain challenges, simplify riser design and minimize both cost and schedule risk. The Lucius field, along with ExxonMobil’s Hadrian South – 8mi from Lucius – tie back to the new spar facility. The Lucius project was brought online only three years after it was sanctioned and five years after its discovery.

The 110ft-diameter spar was designed for 80,000 bo/d and 450 MMcf/d of natural gas. Reserves will be produced through six initial wet tree wells. Lamey et al. said that the hull team and the subsea engineer team worked together to develop concepts for pull tubes to support six future risers that could accommodate up to 15,000psi riser design for future tiebacks.

Dockwise’s Mighty Servant I carried the Lucius spar from Technip’s yard in Pori, Finland, to Kiewet Offshore Services in Ingleside, Texas, in 2013, and repeated the same journey for Lucius’s sister spar Heidelberg in 2014. Photo from Dockwise.

Big support

The Lucius spar has bragging rights. It is often referred to as Anadarko’s largest spar built to date by the contractors that worked on the development. It is obvious this massive project would need assistance from the world’s largest support vessels.

In 2011, Technip was chosen to provide engineering, construction, and transportation of the Lucius spar hull. A second contract followed in 2012, for the development of the Lucius field. The scope of work included the installation of one flexible flowline, multiple flexible gas lift jumpers; main gas lift and infield umbilicals; subsea distribution units; electrical, fiber optic and hydraulic flying leads. It also called for the design and fabrication of the flexible flowline end termination, fabrication and installation of rigid jumpers, burial of flowlines, flooding and hydro-testing of the flowline system.

Technip’s deepwater pipelay vessel Deep Blue was used for installation work at the field alongside sister vessel, Deep Energy.

Hereema Marine Contractor’s then-newbuild Aegir’s first job was to install risers and flowlines at the Lucius field, while the deepwater construction vessel (DCV) Balder handled the hull and mooring commissioning. HMC’s semisubmersible crane vessel Thalif, capable of lifting 14,200-tonne (15,600-ton), was tasked with Lucius’ topsides installation. The facility weighed an initial 15,000-ton, however, the job was broken into nine lifts, the heaviest of which was 10,250-ton (OE: October 2013).

Allseas’ massive pipelayer Solitare was used to install an 18in oil export pipeline, while Saipem’s Casterone handled the installation of a 20in gas export line. Allseas’ Audacia installed an oil export pipeline end termination in Keathley Canyon 831.

Engineering and subsea development

A view of the 605ft-long, 23,000-ton cylindrical hull of the Lucius spar before it was upended in the Gulf of Mexico in 2013.
Photo from Anadarko Petroleum.

Wood Group Mustang provided front-end engineering design, detailed design, procurement support, and engineering support for the fabrication and offshore construction efforts of Lucius’ topsides. Wood Group Kenny provided detail design, procurement support, and engineering support for fabrication and offshore construction concerning the subsea facilities.

The main model deck structure for the topsides was built at Kiewit Offshore Services’ yard in Ingleside, Texas, along with the temporary work deck, sub cellar module, and stair tower. The topsides’ living quarters were fabricated at Beacon Maritime in Orange, Texas, while the compressor modules, production system, and fuel gas system were fabricated at Dolphin Services in Houma, Louisiana.

Lamey et al. said the spar hull is designed to support the four initial Lucius risers and the two initial Hadrian South risers. Lucius uses four umbilical slots while Hadrian uses one. The risers, Lamey and his co-authors said, have an 8.625in outer diameter with 9300psi (g) design pressure. Each riser pair has a control, chemical umbilical and one gas lift umbilical, the latter will be used for enhanced recovery and flow assurance. The pipeline end manifolds on Lucius come with spare connections for future wells, and come with a removable pigging loop to allow for the tieback of additional structures or fields.

As part of a contract awarded in 2012, FMC Technologies supplied six enhanced horizontal subsea trees rated for 10,000ft water depth and pressures of 10,000psi as well as two production manifolds, and associated tie-in equipment.

Timothy Dean of Anadarko, Paul Haines of Wood Group Kenny, and Marsha Calstrom of EXP Engineering International discuss Lucius’ subsea system in OTC paper 26016-MS, saying the field was developed with six initial wells split between two 8in nominal production loops, each with a six-well manifold. An early discovery well is away from the well clusters and Dean et al. said it is daisy-chained into the west manifold flowline loop. Two other delineation wells are produced back to the east manifold with short step out flowlines, which add some flow assurance complexity.

The authors say at the core of the system are 5x2 10,000psi horizontal subsea trees equipped with a subsea choke and a sacrificial flowline isolation valve. A clamp-type flowline connector is used on the tree and for all flowline jumpers.

Next up: Heidelberg

In late June, Anadarko’s Heidelberg truss spar set sail from Ingleside, Texas, to its future home at Green Canyon block 859 in the US Gulf of Mexico, some 390mi off the Texas coast.

Heidelberg’s topsides, like Lucius, were constructed at the Kiewit yard in Ingleside. The pair’s hulls were constructed by Technip in Pori, Finland. To reach Texas, the Heidelberg spar sailed 7300nm over 27 days from September to October 2014 on Dockwise’s Mighty Servant I.

The 80,000 bo/d, 80 MMcf/d-capacity Heidelberg spar is able to operate in water 5300ft deep. It has a maximum topsides operating weight of 16,000-ton, and a hull weight of 23,000-ton. The spar is 605ft long with a 110ft diameter.

The Heidelberg development consists of six production wells, the standalone spar, two drill centers, dual looped 8in flowlines, and 16in oil and gas export lines.

Anadarko operates Heidelberg with 31.5% interest. Its partners include Cobalt (9.375%), Eni (12.5%), ExxonMobil (9.375%), Freeport McMoRan (12.5%), Marubeni (12.75%), and Statoil (12%).