Semi-submersibles or ship-type offshore mobile units used for exploitation of marginal fields. FPSO provides hydrocarbon processing, storage, and offloading hydrocarbons. The unit can be relocated, but is generally located at the same place for long time. It normally consists of a hull with turret, production equipment on deck, crude oil storage facilities and offloading arrangement. Tanker-type FPSOs, including multipurpose models able to operate as shuttle tankers and perhaps even drilling if required, are proving a popular class for operators seeking cost-effective hulls for either deep-water or small oil and gas fields.
The main aim in the FPSO design is to optimise sea-keeping and stability in severe weather, in order to guarantee uninterrupted operation in extreme weather conditions.