Buzios field development has the potential to implement several production systems due to large reservoir volumes. Considering the oil specification, the drive to use standard solutions already in place in Pre-salt area, associated with the high production indexes of the wells, Petrobras decided to tie back all production wells in satellite configuration. These facts, together with geological hazards in the area, lead to a potentially congested seabed scenario. Hence, FPU positioning has been challenging and demanding innovative engineering solutions to optimize FPU mooring as to overcome these challenges and enable FPU positioning close to wells. This optimization gave birth to new issues, such as risk of clashing between mooring lines and lazy-wave flexible risers. Integrated riser and mooring lines dynamic analysis, together with subsea layout assessment were performed to ensure technical and economic feasibility. Furthermore, due to the Buzios reservoir, well design requirements and subsea layout specificities, all FPU were located on the edge of the reservoir and flexible risers were tied back mainly from only one board of each FPU. Hence, enhancing clearance between bow and stern mooring clusters and the optimization of the risers’ configuration were of paramount importance for enabling most of the risers’ connections on the desirable board. FPU mooring optimization led to up to 30% of mooring lines’ radius reduction (horizontal projection), and an average of up to 500m per flowline reduction, saving CAPEX, OPEX and increasing the return on investment.

When performing any redevelopment or complementary project assessment, there are usually common characteristics that an operator could face, for instance reuse of existing assets, marginal fields, etc. However, due to project development strategies in Petrobras and Brazilian regulation and scenarios, there are some specific additional challenges, such as environmental constraints. This paper aims to present actual case studies from Brazilian fields, highlighting some challenges, opportunities and keys to success with associated results, that ensured projects technical and economic feasibility. By the end of this paper, one should realize that challenges and opportunities faced in Brazilian mature fields' subsea design are often similar from a broad perspective; hence, the keys to success can also be reproduced from scenario to scenario, with few specific adaptations, case by case. Such conclusion allows a portfolio approach, anticipating challenges and, thus, motivating the development of desirable novel solutions, such as new technologies and methods of methods. This will lead to saving costs and reduction of risk and time of deployment.