On the Study of Hybrid Riser with Integrated Tether for Extreme Offshore Conditions in the Gulf of Guinea

This study presents the optimization of the hybrid risers in deepwater applications by the integration of a tether. It analyses the feasibility, impact and essence of attaching Polyester tether to the buoy of a conventional hybrid system using the Gulf of Guinea (GoG) wave conditions, and adopting a water depth of 1800m. The sensitivity of the convectional hybrid riser (CHR) and Tethered-Hybrid Riser system (THRS) were also analyzed and compared to observe its response with respect to effective tension and maximum von Mises stress. The findings reveals that the effective tension and stress experienced a 2.5% and 6.4% reduction for the fixed standing hybrid riser (FSHR) and flexible jumper, respectively; for the THRS when compared to the CHR configuration (with 10-years wave return period). The results also show that there should be appropriate vessel control in order to maintain the best response when in service over 10-year and 100-years extreme conditions. Hence, the Tethered Hybrid Riser System (THRS) yields a significant improvement when compared to the CHR.