FPSO WORLD
Turret & swivel stack
The turret anchors the FPSO in place, and allows the FPSO to rotate freely with wind and current. The swivel transfers the oil and gas from the reservoir via the anchored part of the turret which is stationary to the ship side of the turret which rotates with the FPSO. The turret and swivel allows deployment of the FPSO to locations with severe weather, and ensures safe operation in the most demanding conditions.
Flare tower
The flare tower has a key safety function to safely burn and dispose of gas from the process plant in case of process upsets or in case the gas in the process facilities must be released for other reasons. The flare tower is connected to the FPSO flare system, which collects all relief and gas vents from the process facilities. Flaring of gas is normally limited by using the gas for fuel, gas export or reinjection.
Gas compression
When the gas is separated from the oil it must be compressed and processed to be used as fuel, exported or reinjected into the reservoir. The pressure of the gas is increased in the gas compressor in order to export or reinject the gas. Normally the process includes the treatment of the gas to remove water and liquid hydrocarbons, giving a clean hydrocarbon gas that can be exported, reinjected or partly used as fuel to power the FPSO.
Process Plant
The main process plant on the FPSO is the separation facilities, where the raw well stream from the reservoir is split into stabilised crude oil, hydrocarbon gas and produced water. The oil is heated to boil off excess gas and remove water, thus making the oil stable for storage. Residual oil is removed from the produced water before overboard disposal or reinjection to the reservoir. The most common processing is done via gravity separation in large pressure vessels, taking advantage of the difference in density between oil, gas and water. The stabilised oil is then stored onboard the FPSO.
Heating Medium
Processing of oil requires large amounts of heat to increase the temperature of the well stream sufficiently to enable processing in the process plant.
This heat is supplied via the heating medium system, normally operating with a closed loop of pressurised, heated fresh water, or in some cases steam. The heat is most commonly generated from the hot exhaust coming from gas turbines via large heat exchangers called waste heat recovery units. In some cases supplementary heat is also produced via fired boilers.
Power Generation
Large amounts of power is needed to operate the FPSO, and since operation is normally done in remote areas this power must be generated on board the FPSO.
There are two main forms of power generation, either by gas turbine generators or by steam driven generators. The power generation is fuelled by hydrocarbon gas from the process facilities on board the FPSO, with diesel as backup fuel.
Smaller diesel generators located in the hull supply essential and emergency power if the main power generation is not available, to ensure safe operation of the FPSO.