FPSO (also called a "unit" and a "system") is a type of floating tank system used by the offshore oil and gas industry and designed to take all of the oil or gas produced from nearby platforms or templates, process it, and store it until the oil or gas can be offloaded onto a tanker or transported through a pipeline.
Oil has been produced from offshore locations since the 1950s. Originally, all oil platforms sat on the seabed, but as exploration moved to deeper waters and more distant locations in the 1970s, floating production systems came to be used.
The first oil FPSO was the Shell Castellon, built in Spain in 1977. The first-ever conversion of a LNG carrier (Golar LNG owned Moss type LNG carrier) into an LNG floating storage and regasification unit was carried out in 2007 by Keppel shipyard in Singapore.
An LNG FPSO works under the same principles as an oil FPSO, but it only produces natural gas (condensate or liquefied), which is then stored and offloaded. On July 29th 2009, Shell and Samsung announced an agreement to build up to 10 LNG-FPSOs : http://www.platts.com/Oil/News/7093122.xml?src=Oilrssheadlines1 Likely size and capacity: 456 meters in length and 74 meters in width, with a capacity of 450,000 cubic meters Estimated cost $5b
Oil produced from offshore production platforms can be transported to the mainland either by pipeline or by tanker. When a tanker solution is chosen, it is necessary to accumulate oil in some form of tank such that an oil tanker is not continuously occupied while sufficient oil is being produced to fill the tanker.
Often the solution is a decommissioned oil tanker which has been stripped down and equipped with facilities to be connected to a mooring buoy. Oil is accumulated in the FPSO until there is sufficient amount to fill a transport tanker, at which point the transport tanker connects to the stern of the floating storage unit and offloads the oil.
There are two main types of FPSOs, the converted Oil tanker option or the purpose built option. These might be disconnectable or permanently moored. The FPSO design will depend on the area of operation. In benign waters the FPSO may have a simple shape or it may be a converted tanker. Often an external Turret is applied in such areas e.g. West-Africa. For more harsh environments like the North Sea an internal turret is the likely option and the vessel should have a refined shape. This in order to position itself towards the wind and reduce environmental forces on the moorings. All ship-shaped FPSOs in the North Sea are purpose built and most are permanently moored. FPSOs may also be Semi-Submersible type platforms with storage or cylindrically shaped. These are moored in fixed orientation.
An FPSO has the capability to carry out some form of oil separation process obviating the need for such facilities to be located on an oil platform. Partial separation may still be done on the oil platform to increase the oil capacity of the pipeline(s) to the FPSO.
Floating Production, Storage and Offloading vessels are particularly effective in remote or deepwater locations where seabed pipelines are not cost effective. FPSOs eliminate the need to lay expensive long-distance pipelines from the oil well to an onshore terminal. They can also be used economically in smaller oil fields which can be exhausted in a few years and do not justify the expense of installing a fixed oil platform. Once the field is depleted, the FPSO can be moved to a new location. In areas of the world subject to cyclones (NW Australia) or icebergs (Canada), some FPSOs are able to release their mooring/riser turret and steam away to safety in an emergency. The turret sinks beneath the waves and can be reconnected later.
A Floating Storage and Offloading unit (FSO) is a floating storage device, which is simplified FPSO without the possibility for oil or gas processing. Most FSOs are old single hull supertankers that have been converted. An example of this is the Knock Nevis, the world's largest ship, which has been converted to an FSO to be used offshore Qatar.
A LNG floating storage and regasification unit (FSRU) is a floating storage and regasification system, which receives liquefied natural gas (LNG) from offloading LNG carriers, and the onboard regasification system provides natural gas send-out through flexible risers and pipeline to shore.