An FPSO (floating production, storage and offloading vessel) is a ship-shaped offshore facility that processes the raw stream from subsea wells, holds the resulting crude in its own hull tanks, and periodically offloads it to a shuttle tanker. Storage is the defining feature. That is the whole difference between an FPSO and an FPU, and it is why oil fields far offshore get FPSOs while gas fields, whose product leaves continuously by pipeline, do not need one. It also changes the risk picture, because the process topsides, a large crude inventory, and the accommodations all sit on the same hull. The consequence side of the hazard and risk assessment (H&RA) is heavier than on a facility that exports everything as it is made.
Functional safety relevance: Yes. An FPSO is a full process plant on a hull, so the topsides safety instrumented functions are specified, verified, and proof tested under IEC 61511 exactly as they would be onshore.
Key Points
- Processes the wellstream, stores liquid hydrocarbons in the hull, and offloads to a shuttle tanker. The storage and offloading is what the “SO” adds.
- Chosen where oil is produced in deep water with no export pipeline to shore. Brazil, West Africa, and the North Sea run large fleets of them.
- On the US Outer Continental Shelf it counts as a floating production facility under BSEE, which is a different regulatory path from the one a drilling unit follows.
Example
BW Pioneer, the first FPSO approved for the US Gulf of Mexico, produces the Cascade and Chinook fields in roughly 8,200 ft of water. It treats the wellstream on board, holds up to 500,000 barrels of oil in its hull, and transfers that oil to a shuttle tanker rather than sending it ashore by pipeline. Its turret is disconnectable, so the vessel can leave the field ahead of a hurricane.
See Also: FPU, FLNG, FSO, BSEE
Cited Sources
- API RP 2FPS, Planning, Designing, and Constructing Floating Production Systems
- ABS, Guide for Building and Classing Floating Production Installations