The oil received from a subsea oil and gas field is not immediately ready for the refinery, as it always comes with water, gas, etc. This is why a process installation is essential.

An FPSO is equipped with hydrocarbon processing equipment for separation and treatment of crude oil, water and gases that arrive on board from sub-sea oil well reservoirs via flexible pipelines. The separation process is a fundamental part of all hydrocarbon production. The aim for operators is to produce oil free from gas and water, remove all liquids from gas, and discharge produced water overboard well within the environmental limits. Alternatively, water maybe injected into the reservoirs.

Treated oil is transferred to cargo tanks in the FPSO ship’s hull. Treated gas is either re-injected back into the reservoirs or exported through a pipeline to shore.

Water and gas injection refers to methods where water and gas are injected back into the subsurface oil reservoirs via injection wells, usually to increase pressure and thereby stimulate production to increase oil recovery from an existing reservoir.

Alternatively, gas maybe reinjected into an underground reservoir to store and save it if it cannot be exported to shore.