Perdido Field: New Frontier in Ultra-Deepwater Development

The differences between deepwater exploration on the US and Mexican sides of the Gulf of Mexico could not more clearly reveal the contrast that has come as a result of two different oil and gas development strategies. Over the last decade, companies working in the US sector have invested billions in cutting edge, record-breaking deepwater projects, whilst Mexico is still in the preliminary stages of its exploration drilling programme.

The Perdido project – the most technologically advanced ultra-deepwater project in the world – developed by Shell in collaboration with partners BP and Chevron, is located 354km away from Galveston, Texas, and sits very close to the Mexico-US maritime border. The project comprises a spar production facility, which produces from three fields: Great White, Silvertip and Tobago. All three are located in what is known as the Perdido folded belt in the northwest section of the Alaminos Canyon outer continental shelf. The water depth in the region ranges from 2,300m to 3,000m, some of the deepest waters in the Gulf. Perdido began production in 2010, breaking the record for water depth by over 50%.

Work on the three fields, which are spread over a 70km2 area, began in 2002 with the discovery of the Great White field. The semi-submersible Deepwater Nautilus drilled the first five appraisal wells. The Nautilus drilled the first well to a depth of 4,856m, and spudded the final well in March 2004. Shell operates the field and holds a 33.34% stake, while Chevron and BP each hold a 33.33% interest.

The second field discovered in the region was Silvertip, which is 60% owned by Chevron. Shell participates in the field with the remaining 40% interest and is the operator. Shell discovered the field in 2004. Located under 2,804m of water, the field’s final drilling depth reached 4,504m.

Tobago completes the trio of fields that the Perdido production spar will exploit. Work at the Tobago field is the world’s deepest subsea completion to date, and breaks the record previously held by the Silvertip field. Located under 2,926m of water, the well was drilled to a depth of 5,642m with a sidetrack well drilled to a depth of 5,616m. The field is 32.5% owned by Shell, with Chevron holding a 57.5% interest and Nexen holding the remaining 10% interest.

Although the fields were discovered by 2004, development did not begin until July 2007, when the Noble Clyde Bourdreaux semi-submersible began work. In order to reduce both cost and environmental impact of drilling multiple wells at fields located at water depths far greater than any other project in the world, the operator took the decision to use a production spar instead of a tension leg platform. Subsea development of the fields began soon afterwards.

Several different multinational service companies collaborated to put together one of the world’s most technically demanding offshore projects with a number of innovative solutions to cope with the unique nature of the project. Oceaneering International was responsible for the fabrication and installation of subsea hardware at the project, including flowlines and well jumper spools, as well as a pipeline tie-in sled. FMC Technologies worked on Perdido’s subsea completion and processing systems, comprising 17 subsea trees, two subsea manifolds, five subsea caisson separation and boosting systems, controls for both topside and subsea, and related subsea equipment. FMC was also responsible for providing steel catenary risers, top tension risers and umbilicals for the project.

The transport and installation of Perdido’s subsea production umbilicals was done by Acergy North. This included the provision of 60km of steel tube super duplex subsea production umbilicals, four of which were dynamic and three static, as well as the associated flying leads and subsea hardware.

In order to connect the spar to the wells of the three fields, five risers drop from the platform to the seafloor, which branch out to connect to 22 wells, and extend more than 4,267m from the platform. Baker Hughes provided the electric submersible pumping systems (ESPs) to the Perdido spar, whose 1,600 horsepower systems will combat the problem of pumping oil to the surface at such high pressures. Meanwhile, gas will be separated on the seafloor and sent to a separate production unit on the platform.

The spar hull itself was installed in 2008, after completing a 13,200km journey from the construction yard in Pori, Finland where Technip built the equipment. Once the spur was towed into position, it was rotated from a horizontal to vertical position by pumping water into tanks at the bottom of the spar; the process took more than 20 hours to complete. Once the spar was upright, nine chains and polyester rope mooring lines 3km in length were used to secure the spar to the seabed. Heerema Marine Contractors was responsible for installing the world’s deepest permanent mooring anchor pile in 2,632m of water using the deepwater crane vessel Balder.

The three topsides of the platform support oil and gas processing units, living quarters for 150 people and a drilling rig. In mid-March 2010, the project reached another milestone when Heerema’s Thialf crane barge installed the spar platform’s 9500 tonne topsides. The completed platform is 267m tall, with the spar hull accounting for 173m of this. The life expectancy of the spar is 25 years. Although Shell never disclosed the total project cost for Perdido, experts estimate that the project cost around US$4 billion to complete given the unique and ground- breaking nature of the installation.

The spar acts as common processing hub for the three fields, and the drilling rig attached to the platform and the nature of the floating unit means that by adjusting the tension of the mooring lines, Perdido is capable of direct vertical access to 22 wells in the Great White field. It can also gather, process and export production within a 48km radius of its location.

Production began at the end of March 2010 from five wells at the Great White field, with all wells expected to come online by 2016. The spar was designed to produce 100,000 bbl/day and 200 Bcf/day. Russ Ford, Shell’s technology Vice President for the Americas, said: “Perdido is a technological tour de force that is opening up a new frontier for global oil and gas production. Once the global economy recovers, the energy challenge will return with a vengeance, and new sources of energy will be required. Producing oil safely and responsibly this far out and this deep should allay concerns about industry access to the 85% of the US Outer Continental Shelf that remains undeveloped.”