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The exploration and exploitation of North Sea gas/oil fields in response to market demand is discussed with particular reference to technical solutions for the development of testing programmes and relatively small deposits including the conversion of older tankers to Floating Production and Storage (FPSO) units with export by shuttle tanker and the range of handling and mooring systems available for early production (EPS) and life of field (LOF) applications.

PROJEMAR has experienced several different designs for the Brazilian offshore basins with a great number of them in FPSO.s. The critical point of the structural conversion of the old VLCC.s in FPSO.s is the topsides supports structural arrangement. The deck structures of tankers were originally designed for no loads on deck besides the environmental conditions. Then they have to be strongly modified to support the big additional loads from the topsides. However the free area of the hull deck gets very congested when the topside facilities are installed. Then it becomes a challenge to optimize the structural impact of the topside supports into the whole general arrangement. PROJEMAR then defined a typical VLCC hull to study the optimum topside supports in FPSO conversions. The analysis of the hull structure should address stresses buckling and fatigue. The stress and buckling criteria were based on ABS Rules for Vessels and FPSO.s. The fatigue analysis was carried out according to ABS recommendations. Three different solutions are addressed in this study: the truss supports the stools supports and the partial bulkhead supports.

ABSTRACT This paper describes the non-linear time-domain dynamic analyses of a Free-Hanging Catenary flexible riser system in nearly 900m (3OOOft) water depth. The analyses are related to the conversion of a 27OKdwt tanker into a Floating Production Storage and Oftloading (FPSO) unit. Individual risers were modeled using a Finite Element technique. A non-linear time-domain analysis was performed for individual risers under extreme survival conditions with both intact and damaged mooring systems. A coarse mesh was first used as a cursory investigation method to study the overall behavior of all representative riser sizes. Finer meshes were then used to further analyze some specific dynamic behavior of the two extreme riser sizes. The sensitivity of the results to modeling approach is studied and the issue of potential dynamic instability is discussed.

Conf held 22-23 June 1994 in Aberdeen UK. Papers are - Maximising flexibility and cost efficiency of field development by utilising new STL and STP technology on floating production systems Optimising field economics and overcoming operational difficulties of using an FPSO to develop a marginal field Accelerating the use of FPF's through exploiting innovative financing solutions Choosing between new build and conversion of an existing semi-sub or tanker on a fit for purpose basis Successfully meeting certification and regulatory standards for floating production systems Improving project economics (operating and export) through the use of cost effective floating storage facilities Cost effective solutions to the problem of associated gas Harnessing newly available technology to maximise the economic potential of FPSO's Practical interactive workshop - lifecycle costing for FPSO's