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  Woollybutt Project Overview
Woolybutt Project history

EAL contracted to Premuda to enable the development of the Woollybutt field.  Premuda’s scope of work encompassed:

          The provision and installation of the Floating Production Storage and Offloading (FPSO) facility and all related facilities from the wellhead to the end of the offloading hose; and

          Operation of the facility for an estimated six years, then decommissioning and abandonment.

Premuda carried out the detailed design, procurement, fabrication, tanker conversion and FPSO installation for the development. 

Australian FPSO Management, (AFM), a 100% owned subsidiary of Premuda are sub-contracted to provide operational personnel, management and infrastructure to operate the production facilities and FPSO on behalf of Premuda.

The development consisted of the following primary elements:

          Converted trading tanker (formerly the “Four Lakes”);

          Production and support facilities;

          Disconnectable single point mooring (DSPM); and Subsea Facilities.

Conversion tanker – MT “Four Lakes”

The vessel “Four Lakes” has been converted to the FPSO “Four Vanguard”, suitable for the field life.  The basic details of the “Four Vanguard” are as follows:

Vessel Details

Vessel Name Four Vanguard

Flag State

Cayman Islands

Year Built

1992, Fincantieri, Italy, converted 2002/2003


Four Vanguard Serviços e Navegação Lda




* 100-A.1.1 Navil-CST (Oil) ESP-1AQ-1-11Q

DWT (Summer)

94,225 mt

Length Overall

223.3 m

Beam (Extreme)

42.6 m

Cubic Capacity

101,854 m³ (600,000 BBLS)

Cargo Tanks


Double Hull


Ballast Pumps

2 x 1500 m³/hr

Inert Gas System

9400 m³/hr

Mooring Winches

6 x 20 mt


Produced crude is stored in the FPSO hull and offloaded via existing offloading pumps to a trading tanker.  Produced water and seawater are discharged directly overboard.  Off-spec produced water is routed to the slops tanks using actuated diverter valves until the produced water meets specification.  Open drains fluids are routed to the slops tank via deck seals with high deluge rates routed directly overboard.  On-line oil-in-water analysers are provided for treated produced water and for treated slops water discharge. 

A steam power generation package has been added to the FPSO, with two deck-mounted boilers and a turbo alternator located in the engine room.  These facilities have been integrated with the ship’s power system, such that the new facilities normally provide power throughout the FPSO.

The flare system consists of a flare knock out drum, flare tower and pipe flare tip which is suitable for continuous flaring of initial excess produced gas and for emergency flaring. 

The process control electrical module (PCEM) is located on the deck, just aft of the process, and contains high and low voltage distribution switchboards, control panels, DC systems and AC systems to support the operation and control of the production facilities.

A new, fully hydraulic offshore marine pedestal crane has been installed on starboard side of the ship, adjacent to the process facilities.  The crane is utilised for handling general ship supplies, process spares and performing personnel transfer between the FPSO and other vessels.  The crane is appropriately rated for personnel transfer.

Crude is exported by means of a crude offloading system, through metering equipment to the tanker.  The system includes means of assisting the tanker to remain on station.   An anti-pollution breakaway coupling is provided in the offloading hose to minimise the risk of pollution.  This is a dual valve type to ensure that potential spillage is reduced as far as possible, in accordance with project and corporate HSE policies.

A helideck suitable for a Super Puma L332 has been added to the port side of the accommodation.  The accommodation has been modified to suit a normal crew level of 18 – 20 personnel, with facilities available for up to 40 personnel. 

A new free fall lifeboat suitable for 44 personnel has been positioned on the stern.

Disconnectable single point mooring

The FPSO is moored with a disconnectable single point mooring system (DSPM).  The DSPM incorporates a disconnectable riser buoy which drops to a predefined depth when the FPSO lets go.  The FPSO is only anticipated to leave the field due to extreme weather conditions.

A six line mooring configuration is employed, with the mooring lines connecting to the riser buoy.  The buoy is held in place by a hydraulic QCDC clamping arrangement within the moonpool.  The top half of the QCDC structure is joined to the FPSO via a turntable and bearing, which enables the FPSO to weathervane around the buoy.  Drag anchors are connected to the end of each mooring line. 

Subsea facilities

Two subsea-completed wells are individually tied back to the FPSO via production and gas lift flexible flowlines and risers. The wellhead valves are controlled via direct hydraulic control from the control panel located on the FPSO.  The umbilicals include hydraulic hoses, chemical injection hoses and twisted pair wiring for reservoir performance monitoring. 

The risers, flowlines and umbilicals are each in one continuous segment with one end fitting at the wellhead and one at the top of riser buoy.  There are no intermediate connections.

The risers from the FPSO riser buoy to the seabed use a “Lazy S” configuration with a “mid depth” buoy, anchored to the seabed by a gravity base, providing the buoyancy. 


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