Parametric analysis on the global design of flexible riser under different environmental conditions using OrcaFlex

Abstract

The application of flexible risers has led to increased production of fluid contents in the marine industry. This paper presents the design challenges of a flexible riser subjected to internal pressure under deep-water conditions, at a water depth of 2000 m. Parametric variations with extensive dynamic analysis were carried out. The study highlights include the global analysis of lazy-wave configuration for the design of flexible risers, to understand the failure of flexible risers and application of hybrid configurations on flexible pipes. For the global analysis, the design of the riser was modelled in OrcaFlex by considering different sections and then analysed for the influence of effective tension, bending moment and environmental conditions. This riser model is multi-layered and was mainly subjected to the fluid pressure load and the environmental load. Model validations were performed with existing lazy-wave models. In the global design, the riser was assessed when connected to the vessel, but vessel motion was not included, additionally, three different environmental conditions were applied on the model. Also, the suitability of the adopted configuration for the proposed flexible riser was adopted considering it as a sustainable marine structure. Stress profile, tension profile and bending moment for the risers were presented and conclusions were made on the study. Some fatigue study is recommended in future study to be undertaken on the riser.