Optimization of Mooring System Design of Offshore Platforms

Anderson Takehiro Oshiro (Petrobras)

Buzios field is one of the world’s biggest deepwater offshore oil fields. Its development has the potential to implement several production systems due to large reservoir volumes. Many offshore platforms close to each other, together with geological hazards in the area, lead to a potentially congested seabed scenario. Hence, Platforms positioning has been challenging and demanding innovative engineering solutions to optimize Platforms mooring as to overcome these challenges and enable Platforms positioning close to wells.

This optimization gave birth to new issues, such as risk of clashing between mooring lines and 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 Platforms were located on the edge of the reservoir and flexible risers were tied back mainly from only one board of each Platform. 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. Platform 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.