State-of-the-Art SCR Qualification Program for 24 inch × 40 mm Thick Clad Pipe with Upset Ends for the Browse Project
Authors: Mekha Basim , Hawkey Ben , Chandler Bruce D. , Fazackerley Bill , Stevens Donald M. 
Published: June 2014

This paper describes a comprehensive and state-of-the-art steel catenary riser (SCR) qualification program that was undertaken by Woodside Energy Limited (Woodside) as operator of the Browse LNG Development on behalf of the Browse Joint Venture participants for their original Browse LNG Development concept (Browse to Kimberley subsea development and onshore processing concept). The Browse LNG Development comprises of three distinct fields, Calliance, Brecknock and Torosa, and is located offshore Western Australia. The objective of the program was to demonstrate the feasibility of using corrosion- resistant alloy (CRA) clad 24 inch Outside Diameter (OD) × 40 mm Wall Thickness (WT) Wet Gas Export SCRs for the Browse project, in approximately 600 m water depth. CRA clad SCRs of such a large size have not been installed previously and no CRA clad SCRs of this size have been used in such relatively shallow water.

The combination of a large diameter pipe with a high design temperature in relatively shallow water SCRs presented a design challenge. CRA clad pipe was required due to the corrosive fluid and high temperature combination. In addition, upset ends for the SCR touchdown area were needed to meet the fatigue life requirements. Clad pipe production, CRA welding of 40 mm thick pipe and Automated Ultrasonic Testing (AUT) inspection of such girth welds has not been done previously in either pipeline or 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 the probability of success and to explore different pipe manufacturing methods. The bodies of some pipe joints were externally machined to form upset ends, which were needed to satisfy the fatigue requirements of the SCRs. A weld procedure qualification program was conducted for the girth welds, to demonstrate that CRA welds would be able meet the typical but usually stringent requirements for SCRs. This included a full-scale fatigue test program, to establish the applicable design curves for the welds. Finally, three Automated Ultrasonic Testing (AUT) inspection companies performed AUT of seeded defect welds, to demonstrate 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 to successfully 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 the contractors to extend their capabilities beyond normal SCR requirements by encouraging them to develop innovative 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 the qualification 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 program was very challenging in all aspects, but succeeded in achieving its overall objectives.