FPSO Nan Hai Sheng Li Internal Permanent Turret
Scope of Work
SOFEC designed, constructed, and installed an internal permanent turret mooring system for the MODEC-converted 140,000 dwt Nan Hai Sheng Li FPSO.
The permanent turret mooring system installed in the FPSO enables the tanker to remain on station during 100-year typhoon conditions characterized by wave heights up to 13.2m, currents more than 3 knots, and 87 knot winds. The Liuhua 11-1 field is located in Typhoon Alley offshore, southeast Hong Kong, PRC. The Nan Hai Sheng Li FPSO survived a direct hit by Super Typhoon Sally in 1996. The FPSO has a design life of 15 years.
The dual toroidal swivel system on this FPSO, as well as the piping and riser systems, was designed for H2S service.
General Description
| Client Name: | Amoco Orient Petroleum Co. |
| Contract Award: | July 1993 |
| Installation Date: | March 1996 |
| First Oil: | April 1996 |
| Vessel Size: | 140,000 dwt |
| Storage Capacity: | 650,000 bbls |
| Water Depth: | 305m (1,000ft) |
| Fabrication: | Turret - Japan Vessel - Singapore |
Design Environmental Criteria
(100-year storm)
| Significant Wave Height: | 13.2m (43.2ft) |
| Wind Velocity: | 45m/s (87 knots) |
| Current: | 2.26m/s (4.39 knots) |
Mooring System
Turrets
10×1 chain-wire-chain with subsea buoys (inverted
catenary mooring):
4.5-in. ORQ +20% chain
4.5-in. Spiral strand wire rope
Syntactic foam support buoys
40mt High holding power anchors
Internal Permanent Bow
The 6.5m internal turret houses a four-pass swivel, with toroidal passages for two production lines, one test line and one spare line. A hydraulic swivel for control lines is also included. Hydraulically activated emergency shut down valves were placed below the swivel as part of the FPSO safety.
Fluid Swivel Assembly
| 2 x 12-in. 300# ANSI flange connection (740 psi design) |
Riser System
2 x 13.5-in. Flexible riser
1 x 6-in. Flexible riser