Following the tendency of using steel catenary risers (SCR's) for export lines in Campos Basin, PETROBRAS developed a project for installation of two 12" oil export SCR's in the semi-submersible platform P-19, at Marlim Field, in a water depth of 770 meters. The platform will be taut leg anchored with 16 polyester chain lines. The risers will be connected to the portside platform pontoon, in order to minimize the action of the waves directly on the risers and for safety reasons. This paper describes the design, components, specification and installation of the SCR's.
To continue the development of exploration and production of Campos Basin, PETROBRAS will install in 1997, the P-19 platform, a taut leg moored semi-submersible platform located in the Marlim Field, in 770 m of water depth. The production will flow through flexible lines, hanging at the spider deck level. The oil will be exported to a Pipeline End Manifold, using two 12" steel catenary risers (SCR) connected to two 12" pipelines.
This solution was first studied in 1987, when PETROBRAS participated in a IIP' developed by SHELL and, since then, further studies were performed by PETROBRAS, at it's Research Center and at the E&P Department, to develop this technology.
PETROBRAS will install its first SCR, as a prototype, in the P-XVIII Semi-submersible platforms, in 910 m water depth, in 1997. This riser will be monitored during one year and the results will be compared with the design data and with simulations that will be performed with computer programs. Stresses, vibrations due to wave forces and vortex shedding, offsets and platform motions will be measured. Metocean data, including directional waves, currents and wind will be monitored too. This riser will be connected later in the end of 1997 with flexible lines, to the P-26 Platform.
The function of a mooring system is to restrict the lateral motions of the floating structure within specified operational constraints. The overall design parameters are typically in terms of maximum allowable offsets, varying according to the platform operating conditions and the riser requirements, with limitations on maximum mooring line loads and other more specific constraints.
The design loads on the system are generated by wind, waves and currents. The mooring system operates by developing horizontal components at the points of attachment to the floating structure.
The polyester rope taut leg mooring concept allows cost reduction and improves the station keeping performance3. In the taut leg geometry, the platform mooring lines are terminated with suction piles or vertical loaded anchors, as showed in Fig. 1, to develop higher horizontal components, resulting in reduced mooring pattern radius around the platform.
