The FPSO Espirito Santo, located offshore Brazil in the Parque das Conchas (BC-10) field, is the world's first turret moored FPSO to use steel risers for fluid transfer. The FPSO is moored in a water depth of 1, 780 meters, and the internal turret incorporates a total of 21 riser and umbilical slots. The steel risers, which are in a Lazy Wave configuration, were pulled into the turret through inclined I-tubes. Clamps at the top of the I-tubes retain the risers, thus transferring axial loads from the risers to the turret. A clamp casting welded at the bottom of the I-tubes houses a stopper arrangement designed to transfer shear forces and moments from the risers to the turret.
The FPSO began oil production in July 2009, and now has over 4 year's optional experience. During this period, inspection of the riser system and the associated flex-joint has confirmed the integrity of the design, giving further confidence in the use of steel risers in turret moored systems.
This paper summarizes the basis for selecting steel risers for the development, how the risers and umbilicals interface with the turret, and the impact of the riser choice on the turret design. The in-service inspection of the riser system is described and the results reported.
