Sparks About Gas

Going big with floating production vessels

 By Nicholas Newman
About gas

Oil and gas Floating Production Storage and Offloading (FPSO) vessels have opened up hydrocarbon reserves too deep for the reach of rigs and often too far from seabed pipelines and coast…

The current population of over 270 oil FPSOs and four mega LNG floating production and storage units, harvest oil and gas from subsea wells at depths of between a 1,000 and 2,000 meters, many miles from shore. The stored processed oil and super cooled gas is most often collected by tanker. Oil FPSOs are now found in the North Sea, the Mediterranean and offshore Australia, Brazil, West Africa and Asia Pacific. Four mega LNG FPSO, also known as FLNG (Floating Liquid Natural Gas) are located in the Barents Sea, off Australia and Sarawak.
The cost of oil FPSOs vary according to size and the age at which they were converted. Around 70 percent of oil FPSOs are converted crude-oil carriers, the remaining 30 percent are new, and therefore more expensive, purpose-built vessels. A high production purpose-built FPSO for a large oil field off Africa costs between $700 million and $800 million. For example, Total’s Girassol oil FPSO, now operating 210 km off Angola cost $756 million. These sums are, however dwarfed by Goliath , the $1.1 billion, floating oil production and storage vessel, now 88 km off northern Norway in the Barents Sea.
The floating production and storage vessels for LNG are the costliest and most are located offshore Australia. Shell’s $14 billion Prelude floating LNG production and storage unit, moored approximately 475km off Western Australia, is the latest in a surge to bring new LNG capacity to Australia.
In addition, Petronas’s $10 billion FLNG facility, the PFLNG Satu, is producing LNG from the Kanowit gas field offshore Sarawak.

Statoil FLNG in the Barents Sea (Thomas Nilsen)

What are they?

In essence, FPSOs are floating production vessels, which harvest oil or gas from subsea wells for processing in their topsides before storage in a double hull, in readiness for collection by shuttle tankers or onward dispatch by pipeline. A variety of oil FPSOs are now operational – from the basic FSO (Floating Storage and Offloading) vessel to the typical FPSO (Floating Production, Storage, and Offloading) vessel graduating to the more complex FDPSO (Floating Drilling Production, Storage, and Offloading). In the case of gas, three FLNG (Floating Liquid Natural Gas) vessels are currently operational around the world, soon to be joined by another off Australia.

How they work

Most oil FPSOs are ship-shaped vessels or barges, anchored to the seabed at multiple points in a turret mooring system, which allows them to rotate freely in response to changing weather conditions. Flexible pipelines bring the oil or gas from subsea wells to the FPSO for processing, storage and dispatch.
Production involves a number of stages, including water separation, gas treatment, oil processing, water injection and gas compression. After processing, the oil is moved to storage tanks in the hull. Gas is super-cooled prior to storage. Subsequently, at regular but frequent intervals, tankers or barges come alongside to collect the crude oil or natural gas for transport to markets. The transfer of the hydrocarbons between vessels is completed using a loading hose.
Alternatively, the FPSO can discharge oil or gas into pipelines connected to the shore. For example, Premier Oil’s FPSO, the BW Catcher, exploits a new find in the Catcher Area Development in the North Sea, sending gas by pipeline to Scotland, while the oil is collected by tanker. With a design life of 20 years of uninterrupted operations, it has an oil storage capacity of 650,000 barrels and a processing capacity of 60,000 barrels per day.
Similarly, the Ichthys gas field, about 220 km off Australia is soon to start production. It will be serviced by a central processing facility, the Ichthys Explorer and the FPSO Ichtys Venturer, which will process, stabilize and store condensate delivered from the Explorer before periodically offloading it to tankers for export. Gas will also be piped about 900 km from the FPSO Explorer to Ichthys ‘onshore processing plant in Darwin.

336-metre long FPSO "Ichthys Venturer"(INPEX)

Advantages of floating production and storage vessels

In 2016, contractor companies, who lease vessels to energy companies, owned around 52 percent of oil FPSOs. The leasing market in oil FPSOs enables smaller energy companies to compete with big energy companies, like BP, Shell and Eni among others, who own the remaining vessels. The current stock of gas major energy companies owns FPSOs.
Beyond their versatility, the principal attraction of FPSOs lies in their ability to drill, extract and produce oil and gas in remote and deepwater locations at relatively low cost and speed for onward dispatch. A prime example is the exploitation of Brazil’s offshore Santos Basin, which lies in 2,000 meters of water with reserves a further 5,000 meters below the seabed, beneath a mix of salt, sand and rocks.

The future

As elsewhere in the energy business, Internet of Things technology is being applied to manage operations on FPSO vessels as part of a drive to increase productivity and reduce costs and this is expected to continue alongside the trend towards larger-sized FPSOs. The forecasts of increasing numbers of FPSOs may be optimistic given the current attractions of onshore shale/tight oil and gas projects. However, rising worldwide demand for gas, especially from China and India, could yet increase demand for FLNG vessels.

READ MORE: The jewel of the indian ocean by Marilia Cioni

about the author
Nicholas Newman
Freelance energy journalist and copywriter who regularly writes for AFRELEC, Economist, Energy World, EER, Petroleum Review, PGJ, E&P, Oil Review Africa, Oil Review Middle East. Shale Gas Guide.