Analyses of SCR with Pull-Tube Using ABAQUS and Flexcom

Abstract

Pipe-in-pipe analyses of in-place SCR (Steel Catenary Riser) within pull-tube (PT) or pull-in analyses of SCR through PT are computationally complicated problems in offshore development in the application of SCR hanging off through PT from a platform such as Spar. In the past, those analyses have been done primarily using ABAQUS, an advanced nonlinear FEA commercial tool. A benchmark study of pipe-in-pipe analysis, i.e. SCR through PT, was conducted to compare the performance of ABAQUS and Flexcom, a package popular in the offshore oil and gas industry dedicated to flexible structures like risers or mooring lines. Both static and dynamic loading conditions, as well as the pull-in process were included in the paper. Bending moment, tension, shear force, and von Mises stress of both SCR and PT were compared. The comparison shows that Flexcom pipe-in-pipe analysis of in-place SCR within PT or pull-in analysis of SCR through PT can obtain satisfactory results in bending moment and stress for both static and dynamic simulations with close agreement with ABAQUS. While the friction between SCR and PT is not accounted for in Flexcom, its effect is mainly on tension especially of PT, and insignificant for bending moment and bending stress, which governs the strength and fatigue performance of both PT and SCR at the upper hang-off region. This study indicates that it could be adequate to use Flexcom to conduct pipe-in-pipe analysis with much better efficiency for analysis of in-place SCR within PT or pull-in analysis of SCR through PT.