FPSO – A Guide to an FPSO

what is an fpso

What is FPSO? Floating Production Storage and Offloading is a core element of the oil & gas extraction and refinement process.

What is FPSO?

At its core, an FPSO facilitates the processing and storage of oil and gas at sea. It stands for floating production storage and offloading (FPSO). These vessels are used extensively by the offshore industry and have become one of the primary methods of oil and gas processing and storage. As its name suggests, an FPSO is a floating vessel that acts as a mobile offshore production and storage facility. They are typically employed and leased by oil and gas companies. The vessels themselves are equipped with processing equipment for the separation, storage and offloading of oil and gas that comes from sub-sea oil wells or platforms. When oil and gas is processed, it is safely stored in the FPSO until it can be offloaded onto a tanker or a pipeline for transportation ashore.

Origins of Floating Processing Facilities

The first FPSO was a converted oil tanker, built by Shell in 1977. Before the time of FPSOs, oil and gas extraction was more difficult and inefficient.

Companies were only able to extract oil and gas from shallow fields, no more than a water depth of 50 metres. Oil and gas had to be transported to land via a subsea pipeline, which is economically unviable at water depths more than several hundred metres and in instances where the seabed oil and gas fields are hundreds of miles away from the shore.

Oil and gas awaiting transport was stored in tankers called floating storage and offload units (FSO). FSOs were used to store extracted hydrocarbons (a mixture of oil, gas and water) and transport it from remote locations such as distant seabeds. However, FSOs can’t process oil and gas, which is where the FPSO comes in.

FPSO definition 

As onshore oil discoveries continue to decline, FPSOs will become increasingly more vital for the oil and gas industry. There are more than 200 FPSOs today operating around the globe. They’re less expensive than traditional offshore oil and gas platforms, more flexible, safer, and time-efficient. Here is a breakdown of the FPSO acronym:

Production – The “P” in FPSO is what separates these vessels from FSOs. Production refers to the processing of oil and gas. Hydrocarbons are produced in seabed wells and this is transported to the FPSO via flowlines and risers. The hydrocarbons are then separated into oil, gas, water and impurities via the production facilities on the deck of the FPSO.

Flowlines – Flowlines carry hydrocarbons directly from seabed well. These can be flexible or rigid.

Risers – Developed for vertical transportation. This is the section of the line from the seabed to the topside.

Storage – Once the oil has been processed, it is transferred to cargo tanks in the double hull of the vessel.

Offloading – Offloading refers to transferring the gathered contents to additional transfer conduits. Crude oil that is stored in the vessel is then transferred to tankers and pipelines heading ashore. Gas is either transported to the shore via pipeline or recycled back into the field to increase production.

Design of Storage Facilities

In terms of design, most FPSOs take the form of a supertanker and it can be difficult to distinguish between the two. The defining visual difference of an FPSO is the processing equipment that is stored aboard the vessel’s deck. Meanwhile, hydrocarbon storage facilities are typically situated  below the hull.

Traditional tankers can be converted to an FPSO, giving them an additional element of flexibility. In terms of mooring, the FPSO vessels can be anchored to multiple points on the sea floor, which is called spread morning, or via a central weather vane.

In addition to oil and gas processing equipment, FPSOs can be expected to have living quarters to provide accommodation for staff during long periods out at sea, along with control rooms, offices and recreational facilities.

Core Components of an FPSO vessel.

Spread mooring: Spread mooring is a traditional mooring system, incorporating a number of mooring lines attached to the hull of the vessel. These mooring lines are anchored onto the seabed.

FPSO turret (weathervaning) – The turret is integrated into the FPSOs hull, so the hull weathervanes around the mooring system and the mooring line. This enables FPSOs to position the vessel favourably against the wind so that it remains bow to wind and weather. A turret mooring system is critical for harsh weather conditions. In essence, the turret enables the FPSO to freely rotate while moored to various locations on the seafloor.

Detachable FPSO turret – Many turret systems allow the turret to be disconnected from the vessel, but remain attached to the mooring lines on the seabed. This is particularly useful in situations such as hurricanes and storms, where the vessel needs to react quickly to external hazards.  Once the threat has been mitigated, the FPSO can return to the turret, reattach and continue operations. This mooring system is by far the most flexible.

Gas dehydration – Gas is often saturated with water vapour, which poses a threat to facilities. Gas dehydration removes the water that is associated with natural gas.

Gas compression – Natural gas must be treated to conform to commercial standards.

Water injection – Water injection is a process where water is introduced into a reservoir to encourage oil production.

Gas, water and oil separator – As water, gas and oil have different densities, they can be separated with gas rising to the top, water on the bottom and oil staying in the middle. Additional debris such as sand will settle at the bottom.

Seawater treatment – Sea water treatment involves removing sulfates and other unwanted elements from injection water.

Benefits of FPSO

Why have FPSOs become so important for oil & gas companies?

Conceptually, FPSOs have given oil and gas companies a lot of freedom and versatility with regards to exploration and extraction. FPSOs enables companies to produce oil & gas and explore increasingly remote areas at a cheaper price in comparison to traditional offshore oil and gas production and storage methods.

Related: 15 Top Advantages or Benefits of an FPSO