The cost effectiveness and technical feasibility of Floating Production, Storage and Offloading (FPSO) systems in regions of harsh seastate environments has been proven in recent years. The Arctic regions challenge further the designer of such systems not only with harsh sea states but also with extreme temperatures, the presence of icebergs and pack ice. In order to avoid unacceptably high design loads on moorings, risers and the hull, and hence reduce costs, it is desirable to be able to disconnect the FPSO from its risers and moorings once conditions exceed certain criteria. The Health, Safety and Environmental aspects of production in iceberg infested waters leads to the requirement for emergency disconnection. The present paper shows the feasibility and highlights the advantages of a disconnectable turret-moored Concrete FPSO in such circumstances. The aspects of reconnection, damage to risers and moorings, and production downtime are addressed. The advantages that are inherent in a concrete vessel in terms of motion behaviour, thermal properties and ice impact resistance are put forward.

Introduction

In recent years DORIS Engineering have invested a great deal of effort in the development of concrete hulled FPSOs for harsh environments. Designs have been developed for areas such as the West of Shetland (Harris, 1996). The advantages in general of FPSOs installed in such areas are well known, indeed the FPSO is often the only technically and economically feasible solution in areas where no infrastructure is present. DORIS Engineering have produced a design for a concrete hulled FPSO which is fully viable, cost competitive, and which presents some unique benefits; for example:

  • Competitive in terms of cost and schedule compared to a traditional steel hull

  • Improved motion performance due to higher inertia relative to a steel hull

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