Nigeria: Total to Start Production from Usan Field in 2012

With oil reserves equivalent to over 30 billion barrels, Nigeria is OPEC’s fourth biggest oil producer. A fraction of those reserves is now to be extracted in the middle of the Atlantic Ocean, 100 kilometers away from Nigeria’s coastline. Unusually, the oil field has no pipeline. Instead, a ship will be used to produce the oil, process it on the high seas and store it until tankers arrive to transport it to land. So we are talking about no ordinary vessel.

A ship without an engine to propel it. An oil field in the middle of the ocean without a pipeline for bringing the oil to land. Something seems amiss. But everything is in perfect order. The solution to the problem of an oil field for which it is not worth building a pipeline is a “floating production storage and offloading vessel” (‘FPSO’ for short). The ship resembles a gigantic tanker, but is used for processing and storing oil and gas rather than transporting them. That is done by tankers that bring the oil to the land. “Total”, the French oil concern, recently contracted the construction of an FPSO vessel at the South Korean shipyard of Hyundai Heavy Industries. The vessel is now on its way to the Usan oil field in Nigeria where it should arrive mid-year.

Without an engine to propel it, it is pulled along by tug boat. The vessel will cover just under 14,000 kilometers. Sailing past Australia, India and South Africa, it will cross from the Indian to the Atlantic ocean, where the Usan oil field is situated around 100 kilometers to the south of Port Harcourt. There, a volume of oil equivalent to 500 million barrels lies under the earth’s crust. Production is scheduled for 2012.

“The oil field is so far from the coast that it would not be economically viable to build a pipeline,” explained Nicolas Lauras from Total. A FPSO is the ideal alternative. The 320-meter long and 61-meter wide vessel takes up the crude oil from the platform, processes it, and stores up to two million barrels of it on board. If 160,000 barrels of oil are produced per day as planned, enough capacity is available on board for ten days, following which tankers arrive and convey the oil onto land for further processing.

Emergency genset provides safety

The FPSO is a special ship in more ways than one. The on-board power supply is not covered by diesel engines, but by gas turbines. 45 megawatts of electrical power are needed for pumping out and processing the oil. If the main power supply does happen to fail, a diesel engine takes over in the farm of an MTU emergency genset. lts output of 1,760 Kilowatts may not be enough for oil production, but is still sufficient to uphold crucial functions on board to prevent danger to human life.

“As far as the engines are concerned, we paid a lot of attention to quality, since we have to be able to count on them,” said Mr Lauras. “One thing is clear: in a high-sea location where millions of barrels  of oil are being stored and up to 200 people are working, nothing can be left to chance. Especially not the emergency power supply, which is subject  to specific safety standards,” explains Robert Wagner, team leader at MTU for applications in the oil and gas industry.

These start with the container which houses the genset. It is specially insulated to protect the genset from damage in ease of fire on board. In the event, the venting slots will close and the engine will be supplied with combustion from a separate duet coming from a ‘safe area’ of the ship. The engine is also equipped with emergency air shut-off flaps which close down the air supply to the engine in the shortest possible time in case of risk. To ensure the highest possible level of safety, the genset is laid out with ‘duplicate’ sensor systems. If one monitoring system fails, the second steps in. Water-cooled exhaust pipes and turbochargers keep the surface temperature of the engine as low as possible to prevent fire in the event of a fuel leak.

Man the pumps!

Even if fire does break out, four diesel engines come to the rescue. These are used to power four gigantic fire extinguishers installed on the vessel. As can be expected, the fire-extinguishing water comes from the ocean. An immersion pump driven by hydraulic engine, which is in turn powered by an MTU Series 4000 diesel engine with 1,600 kilowatt output, sucks up the sea water and conveys it to a booster pump. The booster pump increases the pressure to 15 bar and feeds the water to the duets. The four fire-extinguishing pumps can take up a total of almost 2,000 liters of water per second.

Flexibility a major asset

FPSO vessels have arrived on the scene at exactly the right time. Although the energy sector is characterized by constant change and extreme price fluctuations, in the long term prices rise. With the help of mobile systems, oil can be extracted from remote oil fields under harsh environmental conditions.

“The biggest advantage of FPSOs is their flexibility,” says FPSO expert Nicolas Lauras. If an oil field becomes unprofitable, oil companies can shift the FPSO without problem to a different oil field. However it will be a long time before Nigeria’s Usan oil field gets to that stage. Oil production is scheduled to begin there in 2012. The FPSO vessel set sail in March 2011. Without an engine. To an oil field without a pipeline.

[mappress]

Source:MTU Report 01/11 ;Image: HHI