FPSO Seillean

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Name: FPSO Seillean
Operator: Frontier Drilling
Port of registry: Panama
Builder: Harland & Wolff
Laid down: 18 September 1986
Acquired: 1989
Status: operational
General characteristics
Class and type: Lloyd's: 100A1 Oil Processing Tanker
Length: 249.7 m (819 ft)
Beam: 37 m (121 ft)
Draught: 11.54 m (37.9 ft)
Depth: 20.5 m (67 ft)
Capacity: processing: 25,000 bbl/d (4,000 m3/d)
storage: 310,000 bbl (49,000 m3)
Crew: 85

The FPSO Seillean is a unique dynamically positioned oil production vessel. The name means "honeybee" in Gaelic.


The vessel was designated as a 'Single Well Oil Production Ship' (SWOPS) when constructed for BP by Harland and Wolff in 1989. The vessel was designed for the Cyrus oilfield on Block 16/28 in the UK sector of the North Sea. Later she served on the Donan field. Seillean was sold by BP in 1993 to Reading & Bates.[1] As Brazilian oil company Petrobras took the decision to develop the Roncador field, a four-year charter for Seillean was signed. In 1997-1998, Seillean was upgraded and arrived in Brazil in December 1998.[2]

After acquisition of Reading & Bates by Transocean, the vessel was acquired by Frontier Drilling in 2002.[1]


Seallean is a self contained, dynamically positioned, itinerant test and production Ship. Its principal functions are:

  • To produce crude oil from exploration wells completed on the seabed
  • To store the stabilised produced oil
  • To discharge the stored oil to a shuttle tanker

She is equipped with a flare, two cargo-handling cranes, a process plant inside the hull, a completion tower and crew accommodation. The vessel has a displacement of 79,600t, the capacity to process up to 20,000 barrels per day (3,200 m3/d) of oil and to store up to 306,000 barrels (48,700 m3).

The Seillean is at all times considered a ship and must therefore meet all the Statutory Requirements of the Department of Transport. The Seillean is classed by Lloyd's Register of Shipping as a 100A1 Oil Processing Tanker. When in production mode, maintaining position above the seabed wellheads is reliant upon the dynamic positioning, with the vessel's stern towards the waves and wind, controlled by azimuthing controllable pitch (CP) thrusters.

Shipboard power is provided by a hybrid system of gas turbine and diesel driven generators. These are operated such that when fuel gas is available from production operations, the gas turbine generators generate electrical power. When fuel gas is unavailable, the diesel driven generators provide the power, supplemented by the gas turbine driven generators operating on diesel oil.

The Seillean is capable of discharging cargo oil in the conventional way which tankers do, but during the 1998 upgrade, an offtake reel system was installed which allows a pioneering DP ship to ship discharge of cargo to a DP shuttle tanker.

Extensive fire & gas detection, protection, and extinguishing systems are provided. Monitoring, status indication and control is affected from the bridge.

The Process Cargo Control Room (PCCR) and Machinery Control Room (MCR) panels act as a backup in the event that the bridge is unavailable and provide a monitoring facility for normal operations. The confirmed detection of gas anywhere on the ship, or fire in the Oil Production Facility (OPF), will cause an automatic, orderly shutdown of the process plant.

Dynamic positioning

When the ship is in the production mode (as opposed to Transit/propulsion mode), the vessel is connected to the seabed by the production riser, which has no anchoring effect. Many rigs and FPSO units are often anchored to the seabed. One of the main features of dynamic positioning (DP), is the ability to operate in any depth of water, whereas anchoring is subject to shallower water depths. Therefore the Seillean is almost constantly in propulsion opposed to some rigs and FPSO's which are fixed.

The thrusters are arranged as follows:

  • One Transverse Tunnel Thruster in the Forepeak
  • Two Steerable (azimuthing), retractable thruster units in the forward thruster room
  • Two Steerable (azimuthing), retractable thruster units in the engine room
  • Two Steerable (azimuthing), non-retractable thruster units in the aft thruster room

The Aft Steerable Thrusters are normally used for the Ship's propulsion, when in passage and may be supplemented by Thrusters 4 and/or five in the Engine Room.

Production facilities

When on station, the process plant stabilises the crude oil produced from the subsea wells. Most of the separated associated gas is used to fuel the gas turbine driven electrical generators, with the surplus burnt at the flare.

The Seillean has the following production facilities:

  • 26,500 barrel per day processing plant (gross throughput). Maximum oil production is 25,000 barrels per day (4,000 m3/d) and maximum produced water handling capability is 15,000 barrels per day (2,400 m3/d).
  • Storage and transport facilities for 310,000 barrels (49,000 m3) of oil.
  • A 6-5/8" riser which can connect to a subsea wellhead.

Any water produced with the crude oil is separated and treated, then can be either discharged, via an oil in water monitor, overboard or stored onboard in dedicated produced water and slops tanks.

The stabilised crude oil is pumped from the process plant to six cargo oil tanks. The flow of crude oil into the cargo tanks is metered to fiscal standards.


  1. 1.0 1.1 Brenner, Noah (2010-06-17). "Hayward says spill 'never should have happened'". Upstream Online (NHST Media Group). http://www.upstreamonline.com/live/article218091.ece. Retrieved 2010-06-17. 
  2. "Roncador, Campos Basin, Brazil". Offshore-Technology. Net Resources International. http://www.offshore-technology.com/projects/roncador/. Retrieved 2010-06-17. 

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