API RP2T and RP2FPS: Moving Forward

Abstract API is developing updates for two key floating/tethered system documents for issuance in 2008. Impactful changes in RP 2T based on learnings from the 2004-2005 hurricane season, over 10 years of experience and technology development and metocean changes have been incorporated. Additional criteria regarding tendon loss/damage and an integrity check for conditions significantly above the 100 year design basis will be discussed. API RP 2FPS is being developed using ISO 19904 as a basis (19904 was built upon the current version of RP 2FPS and updated) and " wrapped?? with US Gulf of Mexico specific additions. This paper will present the key changes/additions in these documents and provide a discussion as to the impact. Introduction From the first floating production systems in the 1970's and early 1980's, semisubmersibles, FPSOs, TLPs, and more recently spars have featured prominently in the industry's vision of how to produce oil in deeper water depths. The first floating production system, a converted semisubmersible, was developed in the North Sea for the Hamilton Brothers' Argyle field (1974). The first FPSO was installed on the Shell Castellon field offshore Spain in 1977. The first production TLP was installed in the Conoco Hutton field (1981) in the North Sea. Since then, there have been many floating production systems successfully installed in locations all around the world. The first API recommended practice to address these structures was RP2T, the Recommended Practice for the Planning, Design, and Construction of Tension Leg Platforms, first issued in 1987. Until recently, RP2T was the only issued API document to address floating production systems. Although RP2T was limited to TLP's, it served as a technical basis for other types of structures, along with various classification society documents and European codes. In 2001 the first edition of RP 2FPS was issued. As the industry has developed more experience with these structures, the body of information available for guidance to designers, builders, and operators has expanded, while the methods and practices have evolved and improved. In response to this evolution, API typically issues updates to incorporate the new information. The impetus for issuing an updated RP2T and a new RP 2FPS at this time includes a number of factors. The technology for both FPS's and TLP's has evolved to include varied concepts and configurations. The engineering tools and practices have greatly improved. And finally, the understanding of the environment, especially in the Gulf of Mexico, has changed significantly following the 2004-2005 hurricane seasons. One other evolution in the API offshore structure recommended practices has been brought about by the progress made in the standards developed by the International Standards Organization (ISO). When the ISO first started to develop offshore structure standards, there was a move within API to eventually replace the API RP's in favor of the international standards.