This paper addresses the use of optimization techniques in the design of Compliant Vertical Access Risers (CVAR), a new riser concept that can improve the structural performance of the production system and also provide several benefits such as the use of dry completion. For optimization assessment, geometric parameters are taken as the design variables and the design constraints consider both structural integrity and operational criteria. A multiobjective approach is considered taking into account the structural performance and geometric criteria. Optimal solution is obtained by NSGA-II method. The efficiency of optimization techniques applied to the preliminary CVAR design is highlighted.
It is known that the biggest oil reserves are currently on the continental shelf, in deep (300 m a 1500 m) and ultra-deep waters (above 1500 m), as Brazilian pre salt fields. However, there are several technological challenges for oil exploitation in such fields, e.g. instability of the salt layer, high temperatures and pressures, high waterdepths, among others. In this paper it is considered a scenario of 2200 m of waterdepth. As waterdepth increases it becomes even more complex the implementation of structural systems for offshore oil production. In such a scenario, associated with severe operating conditions, one of the greatest challenges is the definition of a riser system capable of withstanding the high stresses imposed to the structure while still economically viable. Furthermore, at deepwaters catenary risers can also be subjected to high concentrated tension especially at the top connection. Thus studies have been made in order to develop new alternatives for riser geometric configurations (Bell et al., 2005). One of the most recent alternatives under study is the Compliant Vertical Access Riser (CVAR): a rigid riser that has a differentiated geometry and composition, being able to overcome the challenges imposed by great waterdepths.