OTC 21338--Design of the World’s Deepest Hybrid Riser System for the Cascade Chinook Development

摘要

With the successful deployment of the five Cascade & Chinook free standing hybrid risers (FSHRs) in the Gulf of Mexico at a water depth of 8,250 ft in year 2010, hybrid riser technology is adopted for deepwater development worldwide. It is basically a combination of steel and flexible risers with utilization of their advantages and hence offers unique features. The Cascade & Chinook FSHRs set a few new world records such as the deepest installed hybrid risers, first disconnectable hybrid risers, first hybrid riser in severe environmental conditions in the GoM, first hybrid riser designed to accommodate two floater concepts. Compared to other installed hybrid risers worldwide, the Cascade & Chinook FSHRs posed more technical challenges and hence required more engineering effort to come up with robust engineering solutions. This paper addresses the engineering challenges and solutions associated with the detail design of the Cascade & Chinook FSHR system including global configuration, material selection and sizing, component design, global and local analysis, and qualification testing. A brief description of the Cascade & Chinook hybrid riser system is given first together with the highlights of the technical challenges. Secondly, factors affecting the global configuration and local component design are identified and evaluated. The logical procedure for design and analysis of deepwater FSHRs is discussed and presented in more detail. Thirdly, focus is given to the global response analysis including strength and fatigue as well as local finite element analysis of components such as the taper stress joint, buoyancy can, riser top, lower assembly and foundation pile. Discussion is also given to the relationship between engineering design, fabrication and installation, which is of particular interest for this type of riser. And in conclusion, some important lessons learnt from the execution of the Cascade & Chinook FSHR engineering are summarized.