Lessons Learned From the Qualification Program and J-laying Campaign of 12-inch Steel Catenary Risers for the P55 Deepwater Project

Abstract

This paper reports the Lessons Learned from an innovative linepipe solution that was successfully implemented on P55 Deepwater Project. The P55 field is located offshore Brazil, in the northern area of Campos Basin, in a water depth ranging from 1500m to 1900m. The scope of work consisted in engineering, procuring, fabricating and installing 16 rigid Steel Catenary Risers (SCRs), which are the first of their kind in this area. The corresponding 12-inch SCR qualification results are presented in the perspective to show the significant benefits of the technology used and its potential developments to High Pressure & High Temperature applications.In order to meet tight Hi-Lo requirements together with high fatigue performances, innovative Pipe End Design and associated automatic welding procedures were developed and qualified. The paper describes the complete sequence of pipe manufacturing process, from hot-rolling to final machining, which resulted in a concentric and reproducible pipe end geometry, ideal for limiting Stress Concentration Factors.An extensive qualification program of Full Scale Fatigue test was conducted on girth-welded strings and the associated results showed performance levels at least four times above the target curve. Moreover, Lessons Learned from the offshore campaign established that developed Pipe End Design led to significant improvements in welding times and subsequent J-laying rates. Details on how the technology effectively reduces critical times and lowers rejection rates are provided on the basis of the actual P55 offshore campaign.In addition to the advantages detailed in the paper, the presented linepipe solution proves to be also applicable to High Temperature fields, since the enhanced fatigue behavior was found to compensate a temperature derating up to 270°C. In fact, the presented manufacturing and welding technologies have opened the perspective of ongoing Developments, which are believed to bring a reliable solution for combined High Pressure and High Temperature applications.