State-of-the-Art SCR Qualification Program for 24 inch ×40 mm Thick Clad Pipe with Upset Ends for the Browse Project

摘要

This paper describes a comprehensive and state-of-the-art steel catenary riser (SCR) qualification programthat was undertaken by Woodside Energy Limited (Woodside) as operator of the Browse LNG Developmenton behalf of the Browse Joint Venture participants for their original Browse LNG Developmentconcept (Browse to Kimberley subsea development and onshore processing concept). The Browse LNGDevelopment comprises of three distinct fields, Calliance, Brecknock and Torosa, and is located offshoreWestern Australia. The objective of the program was to demonstrate the feasibility of using corrosionresistantalloy (CRA) clad 24 inch Outside Diameter (OD) on 40 mm Wall Thickness (WT) Wet GasExport SCRs for the Browse project, in approximately 600 m water depth. CRA clad SCRs of such a largesize have not been installed previously and no CRA clad SCRs of this size have been used in suchrelatively shallow water.The combination of a large diameter pipe with a high design temperature in relatively shallow waterSCRs presented a design challenge. CRA clad pipe was required due to the corrosive fluid and hightemperature combination. In addition, upset ends for the SCR touchdown area were needed to meet thefatigue life requirements. Clad pipe production, CRA welding of 40 mm thick pipe and AutomatedUltrasonic Testing (AUT) inspection of such girth welds has not been done previously in either pipelineor riser applications. The requirement to achieve high class fatigue performance was another challenge.The pipe for the qualification program was procured from two different mills, to improve theprobability of success and to explore different pipe manufacturing methods. The bodies of some pipejoints were externally machined to form upset ends, which were needed to satisfy the fatigue requirementsof the SCRs. A weld procedure qualification program was conducted for the girth welds, to demonstratethat CRA welds would be able meet the typical but usually stringent requirements for SCRs. This includeda full-scale fatigue test program, to establish the applicable design curves for the welds. Finally, threeAutomated Ultrasonic Testing (AUT) inspection companies performed AUT of seeded defect welds, todemonstrate the capabilities of their systems to reliably size and detect small flaws in CRA girth welds.The details of the SCR qualification program will be presented with emphasis on the steps taken tosuccessfully complete the program and the lessons learned from the challenges that were encountered. The program has pushed the envelope of the industry capabilities and presented a unique opportunity for thecontractors to extend their capabilities beyond normal SCR requirements by encouraging them to developinnovative solutions to achieve an acceptable outcome that meets the stringent SCR design requirements.The paper summarizes the challenges and measures taken to complete the various stages of thequalification program. The results, lessons learned and recommendations from each step of the program,from pipe procurement and welding to AUT inspection and fatigue testing, are presented. The programwas very challenging in all aspects, but succeeded in achieving its overall objectives.