Аннотация:Abstract HP/HT applications in conventional steel grades require large wall thickness for the pipeline and risers. Design of risers with large wall thickness, especially in deep waters and ultra-deep waters, pose great challenges due to: large payloads on the floater, welding of large wall thickness, fatigue at hang-off and touch down point for Steel Catenary Risers (SCR) and Steel Lazy Wave Risers (SLWR). Application of high strength steel for HP/HT application as riser material is an attractive alternative. High strength steel reduces the wall thickness and thereby reduces payloads on floaters. Further, risers with reduced wall thickness have other added cost saving due to reduced buoyancy requirement for SLWR or hybrid riser solutions which can be significant depending on the application. Furthermore, reduced wall thickness improves weldability. The paper addresses the engineering assessment and cost benefits of using high strength steel. Furthermore the paper will present the recent qualification programmes, carried out in collaboration with Vallourec, aimed at validating seamless Grade X80 linepipe material and welding solutions for reel-lay installation. The results clearly highlight the technical and cost benefits of applying high strength steel for HP/HT riser application. Preliminary fatigue test results demonstrate that high fatigue performance can be sustained with established girth welding procedures with appropriate control of pipe fit up tolerances and weld soundness.
