Otimização da configuração de risers verticais complacentes

Abstract

The compliant vertical access risers (CVAR) is a new alternative to overcome the barriers imposed by deepwater fields for oil exploitation in an efficient, safe and economic way. The differentiated geometry of this relatively new riser configuration improves the structural performance of the system. The characteristic compliance of the CVAR system can also compensate for vessel motion. The CVAR, being vertical access to the wells, brings the advantage of using dry trees, and also allows the completion and workover operations to be performed from the FPU, offering significant economic and operational benefits to deepwater oil field development. With the increasing complexity of risers configuration and the constant challenge of minimizing costs and improving the performance of structures, the use of an optimization methodology is of great importance. Based on this motivation, this work presents the study of compliant vertical access risers design using optimization techniques. The parameters that define the geometry of the riser are taken as the design variables and the design constraints considerer both structural integrity and operational criteria. Different approaches of the merit function are assessed, both mono-objective and multiobjective, taking into account the structural performance and geometric criteria. A sensitivity analysis of the riser is also presented to provide a better understanding of its structural behavior, considering both static and dynamic analysis. The optimal solution is obtained by the NSGA-II method, an elitist genetic algorithm. Thus, this work attempts to expose the importance and efficiency of the optimization techniques applied to preliminary design of risers, and also emphasizes the applicability of this concept in the design of compliant vertical access risers, that are innovative structures in the context of oil exploitation in deepwaters.