The majority of Spar hulls have been fabricated overseas on skid ways and transported stateside for quayside offloading using submersible Heavy Lift Vessels. For the Williams Gulfstar 1 FPS (GS1) Floating Production System (FPS) we elected to construct the hull in a graving dock and tow it directly to the installation site. This paper will describe the unique fabrication and installation techniques that were used to build a classic Spar hull within a graving dock, rather than using the traditional skid way and overseas-transport approach. It will also describe the GS1 hull installation campaign including tow to site, upending, and hull and mooring installation.
The overall fabrication approach for the GS1 hull was a stateside program utilizing Gulf of Mexico fabricators. The fabrication portion of the paper will focus on the construction methodology for the hull, including the lessons learned incorporated into the design before the start of construction, as well as those realized during construction that were implemented at site to improve both cost and schedule. The major challenges addressed will include modular fabrication, dimensional control, and sequencing and lifting the modular blocks into the graving dock using one of the world’s largest onshore cranes.
The GS1 installation planning and execution experience will be described with focus on a record-breaking installation program with specific identification of the considerable benefits realized by using a temporary work deck for pull-in of all mooring lines and risers. This paper highlights lessons learned, both good and bad, through the unique fabrication and installation approaches used to safely fabricate and install GS1. These lessons learned are applicable to engineers and planners for the fabrication and installation of a Spar-based FPS.