The development of FPSO capabilities since the first FPSO, Shell's Castellon, was installed in 384 feet of water, or 117 meters, has been remarkable. Over time, the FPSO water depth range increased considerably with advances in offshore technology. Today, the deepest sea bed installation record is held by the SBM-operated Turritella FPSO, installed in Shell's Stones development in the U.S. Gulf of Mexico, at an impressive depth of 9,500 feet (2,900 meters).
With such increased water depths, the processing and storage capacity has also developed accordingly. Some of the most advanced FPSOs process over 250,000 barrels of oil equivalent per day (boe/d), while earlier models had around 30,000 boe/d. Large storage capacity has grown enormously, up from 11,000 barrels in early times to as many as 2.3 million barrels that some giant FPSOs are capable of storing nowadays.
The growth in size and capabilities is also visible in the price tag: The capital expenditures for an FPSO range from $200 million to over $3 billion, depending on size, capability, and project requirements. Such changes in technology showcase the FPSO industry's capability to respond to growing production demand. (1)
The production processes start with extracting hydrocarbons from underwater reservoirs using subsea wells. A network of risers and flowlines connects them to the FPSO, allowing the oil and gas to flow up to the vessel.
Once the hydrocarbons reach the vessel, they undergo a series of processing stages to separate the mixture into its components. In this process, crude oil, natural gas, and water are divided using specialised equipment. The crude oil is sent to large storage tanks located within the FPSO's hull, where it is stored until it can be transported. Natural gas is processed separately; some of it is used as fuel to power the vessel itself, while the excess is either reinjected into the reservoir, flared, or compressed and exported. This depends on the specific setup and infrastructure of the FPSO.
The water separated during the process is often polluted, so it undergoes treatment to meet environmental standards. Treated water can be reinjected into the reservoir to maintain pressure and help oil recovery or disposed back into the sea if it's safe to do so. Other impurities, such as sand or chemical additives, are handled according to strict environmental and safety guidelines.
The FPSO also has facilities to offload the processed crude oil. Once the storage tanks—located onboard—are full, the oil is transferred to shuttle tankers using a system of loading arms or flexible hoses. Next, these tankers transport it to refineries onshore for further processing until it becomes a usable product. What about natural gas? If it's not flared or reinjected, it can be exported via pipelines or in liquefied form (LNG) if the vessel is equipped with the necessary infrastructure.
FPSO safety is the top priority during these processes. Advanced monitoring and control systems detect potential hazards and ensure the smooth functioning of the vessel's equipment. Environmental protection systems, such as spill prevention measures and emissions controls, are also integral to the operation of FPSOs. These systems ensure that the extraction and processing of hydrocarbons are carried out responsibly and sustainably (see also: EHS risk management)
The vessel is designed to ensure it works efficiently, safely, and effectively. The FPSO comprises three main parts: the topsides, the hull, and marine systems, and each part plays an important role in how the vessel operates and handles its tasks. The topside is on the deck and contains all the equipment and facilities needed to process oil and gas. These include machines and systems for separating oil and gas, compressing gas, treating water, and generating power. There are also safety systems, named flare system one, which burns off excess gas to prevent dangerous pressure build-up. Power is supplied using gas turbines or diesel generators, which keep everything running smoothly. The topsides also include living quarters, offices, and control rooms, providing safe and comfortable spaces for the crew.
The main hull keeps it afloat and serves as a storage area for treated oil, which can store millions of barrels of oil in their tanks. The hull is equipped with a ballast system, which helps balance the vessel by adjusting the amount of seawater. This system is crucial for stabilising vessels, especially in rough seas. The hull is also connected to a mooring system that anchors the FPSO. The most common mooring system is a turret, which allows it to rotate and stay aligned with wind and waves, reducing stress on the structure and connecting pipes.
The last part, marine systems, helps the vessel function like a regular ship. These include navigation tools—radar and GPS—as well as communication systems for staying in contact with other vessels and onshore facilities. The FPSO also has an offloading system, which uses pumps, pipes, and hoses to transfer oil to shuttle tankers for transport.
The design and operation of FPSOs come with significant challenges due to the harsh conditions they face - strong winds, high waves, and corrosive saltwater. Strong materials and advanced engineering must be used to ensure they can operate safely and effectively. Vessels are also compact, so their design must carefully balance the need for processing and storage capacity with the limited space available while still ensuring safety and accessibility for the crew - strict environmental and safety regulations add another layer of complexity. FPSOs must include advanced systems to monitor and minimise their environmental impact, protect the crew, and ensure compliance with the rules. Regular inspections and maintenance are necessary but can be expensive and time-consuming, as offshore repairs are difficult to carry out. This increases the importance of building FPSOs with durable materials and systems that require less maintenance.
Recent advancements in technology have dramatically improved vessel's performance, efficiency, and sustainability, addressing longstanding operational challenges. One significant development is the use of modular construction. This method involves building and testing components onshore before assembling them on the vessel, streamlining installation, reducing costs, and minimising delays. It also facilitates easier maintenance by enabling individual parts to be replaced or upgraded without major disruptions. The integration of digital tools has also transformed how FPSOs operate. Advanced sensors with real-time data provide continuous oversight of system performance, allowing operators to anticipate and resolve issues before they become critical. Predictive maintenance reduces downtime, while automation enhances safety by reducing the need for manual intervention in routine tasks.
Efforts to reduce environmental impact have spurred the adoption of renewable energy systems and sustainable technologies on FPSOs. Some vessels now use solar panels and wind turbines to generate supplemental power, decreasing reliance on traditional fuels. Innovative systems like waste heat recovery and carbon capture also help reduce emissions and align with global sustainability goals. Subsea processing has emerged as a complementary innovation, enabling oil, gas, and water separation directly on the seabed. By pre-treating hydrocarbons before they reach the vessel, these systems ease the workload on onboard processing facilities and enhance overall efficiency.
How does the FPSO layout support operations in bad weather?
The layout design for an FPSO is developed in such a way that operational stability and efficiency are achieved even in very harsh weather conditions. The turret mooring system, part of the layout design, allows rotation and self-alignment of the vessel to the direction of waves and wind, reducing structural stress. Its integral hull ballast system changes the balance of seawater in its ballast tanks to maintain stability in heavy seas. Besides that, advanced materials and engineering solutions applied in the design of this FPSO protect it from corrosion and fatigue so it can withstand saltwater and extreme weather conditions. It goes without saying that regular maintenance and inspections ensure further strengthening of structural and operational integrity so that the FPSO can function effectively in unfavourable offshore conditions.
How does an FPSO layout minimise environmental impact?
The layout of an FPSO integrates advanced systems that reduce its impact on the environment. Water treatment systems strategically positioned within the topsides ensure that water discharged back into the ocean meets stringent environmental standards by removing traces of oil and other impurities. Inclusions of green technologies, carbon capture systems, and renewable sources like solar panels and wind turbines are all integrated into the design in such a way as to reduce reliance on fossil fuels. The flare systems, which are part of the topsides, have been designed to burn the excess gas efficiently so as to minimise harmful emissions. Besides, subsea processing technologies supplement the layout of an FPSO in the aspect of increasing the efficiency of operations while minimising environmental footprints related to production activities. The FPSO design makes its operations sustainable and environmentally friendly by following international and regional set environmental standards.
The FPSOs represent a pinnacle in offshore engineering, where advanced technology has been coupled with efficient design to produce oil and gas in the world's most inhospitable areas. Production processes are highly optimised, from subsea extraction to offloading, while their layout integrates several systems within such a compact and dynamic environment. Though challenging, continuous innovations ensure that FPSOs remain at the top of the energy sector and are key contributors to satisfying the global need for energy. FPSOs are bound to be of increasing importance in the production of energy offshore, given the continuing advancement in technology. This, therefore, forms the basis of sustainable and efficient future energy.
Delve deeper into one of our core topics: Personnel on board
Liquefied natural gas (LNG) is natural gas, which is principally methane, CH4, combined with minor amounts of ethane, C2H6 that has been liquefied by cooling to very low temperatures for safe, non-pressurised storage and/or transport. LNG takes up about 1/600th the volume of natural gas in its gaseous state at standard conditions for temperature and pressure.
LNG is colourless, odourless, non-toxic and non-corrosive. Hazards include flammability after vaporisation into a gaseous state, freezing and asphyxia. The liquefaction process removes some components, such as dust, acid gases, helium, water, and heavy hydrocarbons that may cause problems downstream. The gas is subsequently liquefied at near atmospheric pressure by chilling it to around −162 °C (−260 °F); peak transport pressure is limited to about 25 kPa (4 psi) above atmospheric pressure, which is about 0.25 times standard pressure at sea level. (2)
Sources:
(1) https://www.bnamericas.com/en/features/petrobras-working-to-make-fpso-tenders-more-attractive
(2) https://en.wikipedia.org/wiki/Liquefied_natural_gas
(3) https://www.oilandgasiq.com/oil-and-gas-production-and-operations/case-studies/guide-to-floating-production-storage-and-offloading-fpso
(4) https://www.modec.com/business/service/floater/fpso/
(5) https://energymaritimeassociates.com/guide-to-floating-production-systems/