This chapter concentrates on the design philosophy for a Floating Production System (FPS) vessel which is connected to a subsea completion via deployed risers. It is taken that the necessary field studies have already confirmed the choice of an FPS, the solution for drilling, well completion and riser system. The type of vessel is thus very dependent upon the oil export scenario, as storage is important to non-pipeline solutions. The starting point for this chapter is therefore the point when the choice of vessel is being finalized.
The design aspects discussed refer to any type of FPS, but specific proposals are taken from the author's experience of monohull vessels. The choice between column-stabilized or monohull should have been addressed early on in the conceptual stage If both solutions required evaluation then further parallel studies need to be undertaken and comparisons should take into account the whole life cost. A dual-path approach should not be followed if it can be avoided as it requires additional skilled manpower, which is often understrength at the pre-engineering stage.
A review of today's FPS technology Offshore Engineer, 1986 shows that we have very few total solutions that are easily comparable. However, the message of this chapter is that the industry should not ignore what has been learnt so far. This may be difficult, as a lot of the experience is widely distributed in small specialist groups, and often in companies outside of the oil industry designers and contractors It is important therefore that the two basic development engineering traps are avoided.
By nature, engineers are too willing to start work on a weak foundation (of information). Surgeons by contrast, are unlikely to operate without having previously made a diagnosis.
It sometimes appears easier to dismiss previous experience when there have been some problems and try a new approach This can only be justified if one really understands the problem, most engineering progress has been made by learning from our mistakes!
Since the experience relevant to the design of the vessel and the necessary subsystems to support production facilities on an FPS are diversified, the history is important. The two first obvious areas are the traditional marine industry and the specialist marine area of the offshore industry. Unfortunately these two still tend to be quite independent, in spite of efforts by the naval architecture profession. There is a further subdivision which started in the late 1960s when the first harsh-environment drilling units (semisubmersibles and drillships) were being conceived.
Across these boundaries there are areas of technology which are common and are well understood. An example would be dynamic positioning, where there are a small number of experienced designers and manufacturers who serve several other markets as well as the oil industry and with whom there is a good exchange of information.