Mastering the 5 Types of FPSO for Unmatched Offshore Success

Types of FPSO ( Floating Production Storage and Offloading)

FPSO full form is Floating Production, Storage, and Offloading units come in various designs to suit specific offshore conditions, water depths, and production needs. While their core function—producing, storing, and offloading hydrocarbons—remains the same, the differences lie in their construction approach, mooring system, and the type of resource they handle. Below are the primary types of FPSOs and their characteristics.

When planning an offshore oil or gas project, understanding the types of FPSO available is crucial for making the right investment decisions. Each of the types of FPSO—whether it’s a converted tanker, a new-build unit, or a specialized gas FPSO—offers different advantages based on water depth, field size, and production needs. During our consultation, we will assess your field’s conditions and match them with the most efficient types of FPSO for maximum operational safety and profitability. We also evaluate lifecycle costs, maintenance demands, and relocation potential across all types of FPSO. By choosing the correct types of FPSO, you can ensure optimized production, reduced downtime, and a sustainable long-term offshore strategy.

Converted FPSO

These are existing tankers that are converted into FPSOs. They are typically smaller than purpose-built FPSOs, and may have limited storage capacity.

A Converted Tanker FPSO is an offshore oil and gas production facility created by modifying an existing crude oil tanker into a fully operational Floating Production, Storage, and Offloading unit. Instead of constructing an entirely new vessel from scratch, oil companies repurpose an old but structurally sound oil tanker, extending its lifespan and giving it a new role in offshore field development.

Why Conversion is Done

• Cost Savings: Building a new FPSO is expensive and time-consuming. Converting a tanker can reduce capital expenditure by 20–40%.
• Faster Deployment: Since the hull already exists, the project skips the lengthy hull fabrication stage, allowing the FPSO to be ready for operation sooner.
• Sustainable Use of Assets: Converting tankers minimizes waste and makes use of decommissioned vessels that still have many years of operational life left.

Conversion Process FPSO

1. Structural Modifications

• Reinforcing the hull to handle offshore mooring loads.
• Adding a turret system (internal or external) if needed.

2. Production Facilities Installation

• Mounting topside modules for oil/gas separation, treatment, and compression.

3. Storage & Offloading System Upgrade

• Modifying cargo tanks for long-term crude oil storage.
• Installing offloading arms and systems for shuttle tanker transfer.

4. Safety & Environmental Systems

• Installing flare towers, helidecks, lifeboats, and modern safety systems.

Advantages

• Economical – Major reduction in shipyard construction time and cost.
• Speed – Can often be deployed in less than half the time of a new-build FPSO.
• Proven Hull Design – Tankers are designed for heavy loads and ocean travel, making them structurally reliable.

Limitations

• Design Restrictions – Conversion is limited by the tanker’s original hull size and shape.
• Shorter Remaining Life – Converted vessels may have a shorter operational lifespan compared to purpose-built FPSOs.
• Not Ideal for Harsh Environments – Some converted tankers may not be suitable for extreme weather conditions without extensive upgrades.

Newbuild FPSO

These are purpose-built vessels that are designed specifically for use as FPSOs. They can be customized to meet specific project requirements, and are typically larger than converted FPSOs.

A New-build FPSO is a Floating Production, Storage, and Offloading vessel designed and constructed from the ground up specifically for offshore oil and gas production. Unlike a converted tanker, which reuses an existing hull, a new-build FPSO is purpose-engineered to meet the operational, safety, and environmental requirements of its target oil or gas field.

Why Choose a New-build FPSO

• Custom Design: Tailored to the exact production capacity, storage requirements, environmental conditions, and processing technology of the project.
• Harsh Environment Capability: Built to operate in challenging conditions such as the North Sea, Arctic regions, or cyclone-prone waters.
• Longer Service Life: Typically designed for 20–30 years of continuous operation without the need for dry-docking.

Design & Construction Process

Concept & Engineering

• Define production capacity (e.g., barrels per day) and storage volume.
• Specify topside processing modules for oil, gas, and water treatment.
• Design mooring system (turret, spread mooring, or disconnectable).

Hull Construction

• Fabricated in shipyards, often in South Korea, China, or Singapore.
• Built with reinforced steel to handle extreme wave and load conditions.

Topside Module Integration

• Install production units for separation, gas compression, water injection, and power generation.

Commissioning

• Test all systems, safety features, and process flow before deployment.

Advantages

• Optimized Performance: Every system is designed to work seamlessly for the specific field.
• High Capacity: Can handle massive oil production rates and storage volumes.
• Advanced Technology: Incorporates the latest in automation, safety, and energy efficiency.
• Long Operational Life: Reduces the need for major overhauls during field life.

Limitations

• High Cost: More expensive than converting an existing tanker.
• Long Lead Time: Typically takes 3–5 years from design to first oil.

Example

The FPSO Egina (operated by TotalEnergies, Nigeria) is a prime example of a new-build FPSO. It has:

• Production Capacity: 200,000 barrels of oil per day.
• Storage: 2.3 million barrels of crude oil.
• Design Life: 25 years without dry-docking.
  Its purpose-built design allows it to withstand deepwater conditions in Nigeria’s offshore fields while maintaining high safety and production efficiency.

Turret-Moored FPSO:

These FPSOs are moored to the seabed using a turret system, which allows the vessel to rotate around a fixed point. This can help to reduce stress on the mooring lines, and improve the vessel’s ability to withstand harsh weather conditions.

A Turret-moored FPSO is a Floating Production, Storage, and Offloading unit equipped with a turret mooring system that allows the vessel to rotate freely (weathervane) around the mooring point. This design ensures the FPSO can align naturally with wind, waves, and currents, reducing environmental loads on the vessel and improving operational safety.

How the Turret System Works

• The turret is a large cylindrical structure that passes vertically through the FPSO’s hull (internal turret) or is attached externally to the bow (external turret).
• Inside the turret, bearing systems support the FPSO while allowing it to rotate 360°.
• Flexible risers and umbilicals from subsea wells connect through the turret’s central shaft, supplying oil, gas, power, and control lines to the topsides.
• The turret itself is anchored to the seabed using multiple mooring lines (chains, wires, or synthetic ropes).

Types of Turret Mooring

Internal Turret

• Built into the hull, usually in the forward part of the vessel.
• Offers better protection of the mooring system from waves and impacts.

External Turret

• Mounted outside the bow of the FPSO.
• Easier to install and maintain but more exposed to the environment.

Disconnectable Turret

• Can be released from the mooring in severe weather (e.g., cyclones), allowing the FPSO to sail away for safety.

Advantages

• Weathervaning Capability: Reduces structural stress by letting the vessel align with changing environmental forces.
• Safe in Harsh Conditions: Suitable for areas with strong winds, waves, and currents (North Sea, offshore Brazil, West Africa).
• Continuous Production: Maintains stable operations even in rough seas.

Limitations

• Higher Cost & Complexity: More expensive than simple spread mooring.
• Maintenance Requirements: Bearings and swivels must be regularly inspected and serviced.

Spread-Moored FPSO

These FPSOs are moored to the seabed using a series of anchors and chains. They are typically used in shallow water locations, and may have a lower storage capacity than turret-moored FPSOs.

A Spread-moored FPSO is a Floating Production, Storage, and Offloading vessel that is anchored in place by multiple mooring lines spread out in different directions around the hull. Unlike turret-moored systems, a spread-moored FPSO cannot rotate (weathervane); it remains fixed in one orientation throughout operation.

How the Spread Mooring Works

• Multiple anchors and chains (or synthetic ropes) are arranged in a spread pattern, usually with lines from both the bow and stern.
• The mooring system holds the vessel steady, resisting wind, wave, and current forces.
• The risers (pipes from the subsea wells) are routed to one side of the vessel, and their design accounts for the fixed heading.

Key Characteristics

• Fixed Position: The vessel always faces the same direction, usually aligned with prevailing environmental forces for stability.
• Simpler Mooring System: No complex turret bearings or swivels are needed.
• Lower Cost: Installation and maintenance are generally cheaper compared to turret systems.

Advantages

• Cost-effective: Less complex than turret systems, reducing capital and maintenance costs.
• Stable Orientation: Beneficial for operations requiring fixed alignment with subsea equipment or export systems.
• Easier Installation: Particularly suitable for benign (calm) offshore environments.

Limitations

• Not Suitable for Harsh Conditions: Without the ability to rotate, spread-moored FPSOs experience higher environmental loads in rough seas.
• Directional Limitation: If wind, waves, or currents change direction significantly, structural stress increases.
• Riser Design Constraints: Rigid or flexible risers must accommodate the fixed heading without excessive fatigue.

Example Spread-moored FPSO

The FPSO Baobab Ivoirien (offshore Côte d’Ivoire) uses a spread mooring system. It operates in relatively calm West African waters, allowing a cost-effective mooring setup without the need for a turret.

Floating LNG FPSO (Floating Liquefied Natural Gas)

These FPSOs are designed for the production and storage of liquefied natural gas (LNG). They are similar in design to conventional FPSOs, but are optimized for the specific requirements of LNG production.

A Gas FPSO, more commonly known as FLNG (Floating Liquefied Natural Gas), is a type of floating offshore facility designed to produce, liquefy, store, and offload natural gas at sea. It works in a similar way to an oil FPSO but is equipped with advanced processing plants to cool natural gas to around -162°C (-260°F), converting it into a liquid (LNG) for efficient storage and transport.

Why FLNG is Used

• Remote Gas Fields: Allows development of offshore gas fields located far from existing pipelines or onshore LNG terminals.
• Eliminates Long Pipelines: Reduces infrastructure costs and environmental impact compared to building long subsea pipelines.
• Mobility: Can be relocated to new fields after the current field is depleted.

How FLNG Works

Gas Production

• Gas is extracted from subsea wells and sent to the FLNG through flexible risers.

Pre-treatment

• Impurities like water, CO₂, sulfur, and mercury are removed.

Liquefaction

• The gas is cooled to cryogenic temperatures using refrigeration cycles, shrinking its volume by about 600 times.

Storage

• LNG is stored in insulated cryogenic tanks inside the FLNG’s hull.

Offloading

• LNG is transferred to specialized LNG carriers for transport to customers worldwide.

Advantages

• Brings LNG Production to Sea: Enables gas monetization without building costly onshore plants.
• Flexible Deployment: Can be moved and reused in different locations.
• Faster to Market: Avoids delays from complex onshore land approvals and infrastructure building.

Limitations

• High Technical Complexity: Requires advanced cryogenic systems in a marine environment.
• High Capital Cost: Cutting-edge technology and safety systems make FLNG expensive to build.
• Operational Challenges: Requires precise safety measures for handling LNG at sea.

Example Floating LNG FPSO

The Shell Prelude FLNG, operating offshore Australia, is currently the world’s largest floating offshore facility. It is:

• 488 meters long (longer than four soccer fields)
• Can produce 5.3 million tonnes of LNG, LPG, and condensate per year
• Designed to operate for 25 years without dry-docking.

FSO (Floating Storage and Offloading)

An FSO is a floating vessel designed mainly to store and offload hydrocarbons (usually crude oil) from offshore production facilities. Unlike an FPSO, it does not have processing equipment for crude oil or gas treatment — its role is focused on storage and transfer.

Key Features

• Primary Function: Store produced oil until it can be transferred to a shuttle tanker or pipeline.
• No Processing: Oil or gas is typically processed on a nearby platform before reaching the FSO.
• Flexible Location: Can be moored in shallow or deep waters.
• Long-Term Storage: Designed for continuous operation in the same field for many years.

Types of FSOs

• Converted Tanker FSOs – Old crude oil tankers modified for storage and offloading.
• Purpose-Built FSOs – New vessels designed specifically for storage, with improved safety and efficiency.

Advantages

• Cost-effective compared to building pipelines in remote areas.
• Can be relocated to new fields when production ends.
• Suitable for marginal or small offshore fields.

Example of FSOs

• Kraken FSO in the North Sea – stores crude from a subsea production system before export.

Each type of FPSO has its own advantages and disadvantages, and the choice of which type to use will depend on a range of factors, including the characteristics of the offshore field, the production requirements, and the environmental conditions in the area.

Top 10 Frequently Asked Questions About types of FPSOs

1. What is an FPSO?

FPSO stands for Floating Production, Storage, and Offloading unit. It’s a ship-shaped offshore facility that processes oil or gas, stores it in large tanks inside the hull, and transfers it to shuttle tankers or pipelines for export.

2. How does an FPSO differ from a traditional offshore platform?

Unlike fixed platforms that are permanently attached to the seabed, an FPSO is a floating facility that can be moved to another location. It also has built-in storage tanks, which means it can hold hydrocarbons until transport vessels arrive.

3. What types of FPSOs exist?

The main categories are:

• Converted Tanker FPSO – Made from refurbished oil tankers.
• New-Build FPSO – Designed and constructed from scratch.
• Turret-Moored FPSO – Rotates around a turret for better stability.
• Spread-Moored FPSO – Fixed position with multiple anchors.
• Gas FPSO / FLNG – Handles natural gas production and liquefaction.
• FSO – Storage and offloading only, no processing.

4. Why do operators use converted tankers as FPSOs?

Converted tankers are often chosen because they’re quicker to deliver, require less capital investment, and are ideal for medium-term oil field projects where a long-life unit isn’t necessary.

5. How is an FPSO different from an FSO?

An FPSO processes and stores hydrocarbons, while an FSO simply stores and offloads them. In FSO setups, processing usually happens on a nearby platform or onshore facility.

6. What does a turret mooring system do?

A turret mooring system allows the FPSO to rotate naturally with ocean currents, winds, and waves without twisting its subsea risers. This makes it safer and more efficient in harsh marine environments.

7. In which regions are FPSOs most commonly deployed?

FPSOs are especially popular in offshore regions without pipeline infrastructure, such as offshore Brazil, West Africa, Southeast Asia, and the North Sea.

8. How long can an FPSO stay in operation?

Modern FPSOs—particularly purpose-built ones—can remain offshore and operational for 20 to 30 years without returning to dry dock, provided they undergo regular maintenance.

9. What is meant by a Gas FPSO or FLNG?

A Gas FPSO, also known as Floating Liquefied Natural Gas (FLNG), is designed to treat natural gas, cool it to extremely low temperatures until it becomes liquid, store it in cryogenic tanks, and offload it to LNG carriers.

10. What are the main benefits of using FPSOs?

Some advantages include:

• They eliminate the need for costly long-distance pipelines.
• They can be relocated to new fields after decommissioning a site.
• They integrate production, storage, and export in one unit.
• They can operate in deepwater and remote offshore locations.

Conclusion

In summary gaining a clear understanding of the types of FPSO is essential for anyone involved in offshore oil and gas projects. The right choice among the many types of FPSO can significantly impact operational efficiency, safety, and overall profitability. By carefully comparing the types of FPSO, decision-makers can align vessel capabilities with specific field requirements. Whether selecting for deepwater production, storage capacity, or mobility, the types of FPSO available today offer flexible solutions for diverse offshore environments. Ultimately, choosing the correct types of FPSO ensures long-term success and sustainability in challenging marine conditions.