In response to the need for deep water production and storage, further concepts have been developed for this purpose. The Semisubmersible monohull (Semo) is illustrated in Fig. 20.8. The overall design philosophy is indicated in Fig. 20.9.
Fig. 20.8 The Semo
Fig. 20.9 The design philosophy behind the Semo
Figure 20.9 shows two design approaches leading to the same result, and a very logical result indeed. A lot of work has been performed on the concept. Floating structures are more complex to design load wise, there are a lot of parameters that need to be accounted for. Analyses show that the Semo concept is feasible, robust and flexible with regard to most types of offshore developments.
Advanced motion analyses and simulations verify that the concept has superior sea motion characteristics. To further document the motion characteristics, the
Semo was tested in the ocean basin at Marintek, Trondheim. The results from these tests were as expected very positive. So, aspects regarding second-order motions are now considered as solved.
A very simple FSO has been developed lately, as a result of the need for oil storage offshore. The concept has significant similarities to the Semo, but has different design specifications. These concepts have sparked enthusiasm among medium sized ship/offshore yards which do not have their own dry-dock facilities available. They see the concepts as an opportunity to enter the “FSO/FPSO market” which so far has been dominated entirely by ship-shaped solutions.
Local content will be more important in the future, and concrete creates interesting opportunities with regards to local fabrication and assembly. For many countries it is important to build new industry and to further develop the economy. The fabrication of a concrete structure can give significant amounts of work locally, which could give a political advantage compared to structures built in other countries.