An FPSO, or floating production storage and offloading vessel, is a ship-like facility used in the offshore oil and gas industry to process, store, and transfer hydrocarbons from subsea wells. Think of it as a floating factory and warehouse combined: it sits on the ocean surface above an underwater oil field, processes the raw crude that flows up from the seabed, stores it onboard, and periodically transfers it to tanker ships for transport to shore. Around 185 FPSOs are currently installed worldwide, making them the most widely used type of floating production system in the industry.
How an FPSO Works
Oil and gas flow up from wells on the ocean floor through flexible pipes called risers. Once the raw hydrocarbons reach the vessel, onboard processing equipment separates the oil from gas and water. The water is treated to meet environmental standards before being discharged back into the sea, while the oil is routed into storage tanks built into the vessel’s hull. A large FPSO can hold around 2 million barrels of oil at a time.
When those tanks fill up, a shuttle tanker pulls alongside and the FPSO pumps oil through a single discharge line into the tanker’s cargo holds. Roughly 75% of the total storage capacity is offloaded in a given transfer. The sequence of which tanks get emptied and in what order is carefully planned, because draining one section of a massive floating vessel before another can affect its balance and structural integrity.
Main Physical Components
An FPSO has three core sections. The hull is the ship-shaped body of the vessel, either purpose-built or converted from an existing oil tanker. It houses the storage tanks and provides buoyancy. The topsides sit on top of the hull and contain all the processing equipment: separators, compressors, pumps, and safety systems. These are built to the same engineering standards as onshore refineries. The mooring system keeps the vessel in position over the well site despite wind, waves, and ocean currents.
Turret Mooring vs. Spread Mooring
The two main mooring designs reflect different ocean conditions. A turret mooring system connects the vessel to the seabed through a central rotating point. The production pipes pass through this turret, and the entire ship can swing freely around it like a weathervane, always turning its bow into the strongest wind or current. This minimizes the environmental forces acting on the hull and is essential in regions with harsh, unpredictable weather.
Spread mooring is simpler and cheaper. Multiple anchor lines extend directly from the hull to fixed points on the seabed, locking the vessel in a set orientation. Because the ship can’t rotate, this design works best in calmer waters where wind, waves, and current come from a consistent direction. Offshore West Africa is a common location for spread-moored FPSOs. The trade-off is clear: spread mooring saves money on equipment but can’t handle the severe, shifting conditions that a turret system manages easily.
Why Operators Choose FPSOs Over Fixed Platforms
Fixed platforms are steel or concrete structures anchored permanently to the seabed. They work well in shallow water near existing infrastructure, but they become impractical or impossibly expensive in deep water or remote locations. FPSOs fill that gap. They can operate in shallow seas and in ultra-deep water alike, and they don’t require the massive subsea foundations that fixed platforms need.
The biggest advantage is mobility. When a reservoir runs dry or production drops below the point where it’s worth operating, an FPSO can disconnect and sail (or be towed) to a new field. A fixed platform, by contrast, has to be decommissioned in place, a costly and complex process. This reusability makes FPSOs particularly attractive for marginal fields, those with estimated reserves of 15 to 20 years, where building permanent infrastructure wouldn’t pencil out financially.
Many FPSOs are converted from retired oil tankers rather than built from scratch. Converted vessels held 58% of the FPSO market by revenue in 2022, largely because recycling an existing hull cuts both cost and construction time. That approach also reduces the demand for new steel and shipbuilding resources, aligning with industry pressure to limit the environmental footprint of new projects.
Where FPSOs Operate
Brazil dominates the global FPSO fleet. The country has 50 installed FPSOs with another 12 on order, representing about 25% of the world market. That’s more than all of Africa combined (44 active, 4 on order) and more than double the combined count in the UK and Norwegian sectors of the North Sea. Brazil’s deep pre-salt oil fields, located far offshore beneath thousands of meters of water, rock, and salt, are exactly the kind of environment where FPSOs outperform every alternative.
Globally, over 220 FPSOs are either operating, under construction, or available for redeployment as of 2025. About 23 new units are being built, and 12 sit idle, waiting to be refitted and sent to a new field.
Safety and Environmental Rules
FPSOs occupy an unusual regulatory space. They’re not classified as oil tankers under international maritime law, even though many started life as tankers. Instead, they’re treated as floating platforms and fall under specific provisions of the International Maritime Organization’s MARPOL regulations, the main international rules governing pollution from ships. Because most FPSOs stay permanently moored and never make ocean voyages, the standard maritime safety convention (SOLAS) doesn’t apply to them while they’re on station. To compensate, structural inspections follow the same standards required for oil tankers, including regular surveys equivalent to dry-dock inspections.
If an FPSO does need to travel, for repositioning to a new field or for major repairs in a shipyard, it must comply with the full tanker discharge rules during the voyage. Special restrictions also apply in sensitive areas: FPSOs operating in Antarctic or polar waters must follow additional codes governing the types of fuel and oil they can carry.
Life Cycle of an FPSO
A typical FPSO begins as either a new-build vessel designed for a specific field or an existing tanker converted with processing equipment. The vessel is towed to the field site, moored in position, and connected to the subsea wells. Production can last anywhere from a decade to 20 or more years depending on the size of the reservoir.
Once production ends, the operator disconnects the risers and mooring lines. From there, the vessel follows one of three paths. It can be refurbished and redeployed to a new oil field, sometimes on the other side of the world. It can be laid up idle while awaiting a new contract. Or, if the hull is too old or the economics don’t justify an overhaul, it heads to a shipbreaking yard for scrapping. The 12 idle FPSOs currently available for redeployment represent vessels in that middle stage, structurally sound but waiting for the right project to justify their next assignment.