FSO is the acronym of Floating Storage and Offloading used to describe the offshore operation between the oil and gas processing and the export to the shore by pipeline or shuttle tankers.
Originally, all the offshore platforms used to sit on the seabed, but as exploration and production moved to deeper waters and more distant locations in the 1970s, floating production systems were developed.
This can provide an economically attractive solution for smaller oil fields which can be exhausted in a few years and do not justify the expense of installing a pipeline.
Furthermore, once the field is depleted, the FSO can be moved to a new location.
In the early days, the FSO were easy to produce from decommissioned oil tankers.
They were stripped down and tuned to the specific needs of the oil, gas or condensates to be stored and offloaded.
Then they were connected to a permanent mooring point.
Today, there are two main types of FSOs, those built as converted tanker, and those that are purpose-built
The FSO design will depend on the area of operation. In benign waters the FSO may have a simple box shape or it may be a converted tanker.
By definition a FSO has no production capabilities, os it cannot be used alone, but it needs to be integrated in a more complex floating production system where near by offshore platform are drilling and processing the oil and gas.
The decision to split the production units from the storage and offloading facilities may be due to the large size of the equipment or the complexity of the process that prevent them to be installed on the same floating unit.