FPSO Offloading Concepts, their Nautical Feasibility and Safety Assessment

Introduction For the development of offshore deepwater oil or gas re-sources more often F(P)SOs, Floating (Production) Storage Offloading units are applied. For the export of oil (or gas) from the FPSO tankers are used. In the design of a FPSO various options are available for offloading: tandem from a turret moored or spread moored FPSO, tandem from a Single-Point-mooring (SPM) or side by side from a turret moored FPSO. The technical design, but also the nautical operations are highly affected by the choice of the offloading system. Aspects that are affected are:Weather downtime, which effects the overall economic performance of the FPSO;Safety of day-to-day operations, which requires clear procedures, trained personnel and the right type of equipment;Controllability and response in case of emergencies;The overall safety of the operations, the probability of a collision and the related collision energy. All these aspects play a role from day one of the design of an offloading facility until the facility becomes operational. In this paper we will show how various tools, together with experience and common sense can help to take decisions and to prepare people for the offloading job ahead. The paper can be divided in the following main sections:Nautical considerations in the design of an offloading facilityFast-time manoeuvring simulations: operational limits and procedures;QRA, Quantitative Risk Assessment;Real time simulations and training;Conclusions. Nautical considerations in the development of an offloading facility Nautical aspects play a role throughout the development of the F(P)SO. Three phases can be distinguished in this development:Phase 1: Pre-design: selection of concept, selection of location;Phase 2: Design;Phase 3: Implementation and operation. The tools/methods available for the evaluation of the nautical aspects are:Static computations;Fast-time simulations of normal operations;Fast-time simulations of emergency situations;Quantitative Risk Assessment;Real time simulations. The applicability of the various tools in the various development phases is shown in Figure 1, below Figure 1 Tool or methodology to be applied during various development phases (available in full paper) In this first phase: (Pre-design: selection of concept, se-lection of location), the design will focus on the selection of the offloading facility and the selection of the site. Aspects that play a role are, amongst many others, the environmental conditions, type and size of the offloading tanker and the assistance of tugs. Reliable statistics regarding the local climate: e.g.: wind, current and waves are essential to make a reliable evaluation of the various options. In this first phase the methodology for the evaluation of the various concepts is kept simple to be able to make a fast comparison. Experience in combination with static computations or fast-time simulations are the most likely tools to be used.