By Hector Igbikiowubo
SHELL Nigeria Exploration and Production Company, SNEPCo, operated Bonga Floating, Production, Storage and Offloading, FPSO vessel is scheduled to shut down for 4 weeks for the first of a 5 yearly routine maintenance exercise.

It was gathered that the shut-down is planned to occur in phases – from train to train, to minimize volume 225,000 that will be shut-in during the process.

During the process which is scheduled to commence on Thursday, 25th February, 2011 it is expected ‘process valves’ and other defective parts will be opened up and cleaned or changed as part of efforts to get the FPSO back to optimal functionality.
Checks revealed that the Department of Petroleum Resources, DPR has engaged the services of Lloyds, a Register of Shipping for the certification and inspection process, to ensure it meets acceptable international standards.

The DPR superintends activities in the oil and gas industry in Nigeria to ensure standards are adhered to and maintained.

It is expected that the process will be wrapped up with a ‘safety blow-down test’ to verify all systems check, before actual resumption of production, storage and offloading.

The Shell’s Bonga oilfield which was discovered in 1993 has a life span of 20 years; it lies 120km off the coast of the Niger Delta, covering an area of 60km². The Bonga vessel became operational in 2004 and is permanently installed in water depths ranging from 1,000m to 1,125m. First oil production was made in November 2005.

The Bonga FPSO was built by Samsung Heavy Industries in Korea for the owner operator, Shell Nigeria Exploration and Production Company Limited, SNEPCo and the Nigerian National Petroleum Corporation, NNPC.

The hull has a length of 305.1m or 295m between perpendiculars. It has a moulded breadth of 58m. The design draught is 23.4m and it has a scantling draught of 23.9m.

After construction, the 47,200t hull was sailed to Tyneside for the process topsides to be installed by Amec at their Wallsend facility (the ship was one of the largest to ever enter the Tyne). This topside processing system, weighing some 22,000t, was installed on a deck elevated 5.5m above the main deck. Unladen the vessel has a displacement of 90,000t (with topsides installed) and fully laden she has a deadweight of 312,500t.

PROCESSING AND STORAGE ON BONGA FPSO
The processing equipment installed is able to process 225,000 barrels of stabilised crude oil per day. The crude is then exported into a shuttle tanker at a rate of 7,000m³/h (1 million barrels per 24 hours).

Following the completion of the topside installation in 2004, the FPSO sailed to Nigeria and installed on Bonga by means of four groups of three mooring legs to begin operations. The vessel is connected to 16 subsea oil production and water injection wells and the connections use inconel clad Steel Catenary Risers. This is the first time this type of riser has been used on any FPSO.

The Bonga FPSO has a storage capacity of two million barrels of crude oil. The FPSO will also have a gas export facility of 150 million standard cubic feet per day. It can also carry 10,970m³ of diesel oil as well as 138,131m³ of water ballast. Its double bottom is laid out as sludge tanks.

The oil is contained in 15 cargo tanks arranged in a 5 x 3 configuration as well as five pairs of wing tanks full of water ballast. There are two diesel tanks, two methanol tanks and two slop tanks. The methanol tanks are separated from the other compartments by coffer dams.

The product is pumped by 15 hydraulic submersible pumps supplied by Framo, each with a capacity of 1,500m³/h. The cargo and ballast control system is supplied by Nakakita Siesa Kusho.

The width of its double skin is 5.4m. The Bongo FPSO is manned by a complement of four officers and 66 crew that are housed in four single and 33 double rooms.

PROPULSION AND NAVIGATION OF THE BONGA FPSO
The vessel’s power is derived from two diesel driven alternators, each with a capacity of 1,900kW at 1,000rpm. The engines are made by Wartsila and the AMG 630 S6 alternator is made by ABB. The machinery spaces are located under the accommodation deck.

The bridge contains two satellite navigation systems supplied by Invsat. This breaks down into one Inmarsat B unit and one Inmarsat-C T T 30 20 C Saturn B. There is also a FR-2105 radar system.

The safety systems include a Saracom Thorn addressable programmable fire detection system as well as a number of fire extinguishing systems supplied by NK Fire Protection. These include both a foam/saltwater system for the cargo tank deck and a water mist/saltwater system for the machinery room. The lifesaving equipment comprises five 50-person, totally enclosed lifeboats with water break protection.

The waste disposal system was supplied by Team Tec. It consists of an incinerator waste contractor and waste shredder crusher. The sewage plant has been supplied by Hamworthy KSE.

The vessel is classified by Lloyd’s Register of Shipping.