Composite Production Riser Dynamics and Its Effects on Tensioners, Stress Joints, and Size of Deep Water Tension Leg Platforms

摘要

Composite production riser (CPR) joints are being seriously considered in the development of deep water tension leg platforms (TLPs), because of their inherent light weight, superior fatigue and corrosion resistance, and outstanding specific strength and stiffness properties. Current efforts on the development of CPR joints have been mainly focused on low-cost manufacturing and failure strength evaluation of CPR tube body and CPR joint connection. The important issue of system dynamics of TLPs containing multiple CPR strings, has not been addressed.In this paper, system analysis of a TLP containing 16 CPR strings and 12 tendons subjected to Gulf of Mexico environment loading have been conducted. The riser system is configured for 3,000 ft water depth with CPR joints, standard steel riser joints, splash zone joints, stress joint, and top tensioners. The study embraces several disciplines, including naval architecture, riser dynamics analysis, and composite failure mechanics to develop an iterative algorithm for evaluation of the top tension and stress joint requirement. Specifically, optimum top tension requirements have been determined based on riser dynamics and the failure envelope of the CPR joints. For comparison, the optimum top tension requirements are further used to size the TLPs with all-steel riser and with CPR. For the 3,000 ft water depth case study, reduction in riser weight is magnified by 3.31 times in the TLP size. It is demonstrated that the weight reduction in the riser string is nonlinearly related to the tensioner requirement and TLP size.