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AbstractWith deepwater drilling becoming an area of increased interest, the National Institute of Standards and Technology (NISn sponsored composite drilling riser program objectives were extended in 1997 to include a comparative analysis of steel and advanced composite drilling risers for drilling in water depths down to 12,500 ft. A water depth of 12,500 ft was established as the maximum water depth thought to be of interest worldwide. Using requirements established by DeepStar and Reading & Bates, Northrop Grumman Marine Systems and ABB Vetco Gray synthesized a steel drilling riser system and an advanced composite drilling riser system such that the two drilling risers could be compared with regard to key system characteristics such as top tension required, buoyancy required, total system weight and stacked volume. This paper presents preliminary results of the comparative study which identified a weight savings of more than 50% and a volume reduction of 33% as benefits gained by the use of advanced composite materials for fabrication of the riser tubulars. Reduced buoyancy requirements are shown to be a major contributor to weight and volume savings, and also to reduced hydrodynamic drag forces. The comparative analysis performed included dynamic analysis in the hang-off modes using the Northrop Grumman developed Modal Dynamic
189Riser Analysis (MODRAN) program. MODRAN allowed comprehensive 3D analyses of coupled transverse and axial dynamics during hang-off for broad ranges of conditions. The differences (and similarities) in hang-off response are described.