Floating Production, Storage and Offloading

A Floating Production, Storage and Offloading unit is effectively a floating oil-and-gas plant. Moored on station over an offshore field, it takes the well fluids produced from subsea wells, processes them on board (separating oil, gas and water and treating each) stores the resulting crude oil in its hull tanks, and periodically transfers, or offloads, that oil to a shuttle tanker that carries it to shore. This combination of production, storage and offloading in one floating unit lets operators develop fields that are too deep, too remote or too small to justify a fixed platform and a pipeline to shore.

Many FPSOs are converted from large oil tankers, whose hull and cargo tanks suit storage, while others are purpose-built. They are held in position by mooring systems, frequently using a turret that allows the vessel to weathervane — to rotate around the mooring point so it naturally heads into the prevailing wind and sea, reducing the loads on the mooring and the risers. Flexible riser pipes carry the well fluids up from the seabed to the processing equipment, or topsides, mounted on the deck. Because the unit stays on location for many years, often through harsh weather, its design emphasises fatigue strength, safety and the ability to keep producing continuously.

FPSOs are one of several types of floating offshore production system, alongside FSOs, which only store and offload without processing, and semi-submersible and tension-leg platforms. They have become central to deepwater oil development around the world, from West Africa and Brazil to the North Sea and Asia. Operating one combines the disciplines of a ship and of an oil-processing facility, so crews include both marine and production specialists, and the units are subject to both maritime and offshore safety regimes. As oil development moves into ever deeper water, the FPSO remains a key enabling technology.