Dynamic analysis of steel catenary riser with hydrodynamic dampers conveying internal slug flow

Abstract

The steel catenary riser (SCR) employed in ultradeep-water petroleum exploitation is constrained by excessive stress and top tension. The application of discretely arranged low-density coatings, forming an SCR with hydrodynamic dampers (SCR-HD), has been demonstrated to effectively address these problems without significantly extending the length of the riser. In this study, the performance of an SCR-HD was systematically evaluated and compared with that of a typical SCR using the vector form intrinsic finite element method. Dynamic simulations of both risers were conducted under different combinations of internal flows and top-end excitations. The vibrations, internal forces, and fatigue damages of the SCR and SCR-HD were analyzed to determine the effects of slug flow and hydrodynamic dampers. The simulation results indicated that attaching hydrodynamic dampers reduced the tension and stress of the riser and decreased fatigue damage at the hang-off point. However, fatigue damage within the lower catenary region and touchdown zone of the SCR-HD became severe. The top-end excitation contributed the most to the fatigue damage of the risers, and the slug flow induced high-frequency vibration components and amplified internal forces.