A Collaborative Approach to Root Cause Analysis: With Reference to Suncor Energy Terra Nova Flexible Flowlines and Risers

Abstract

One riser and two flowline sections installed in the Suncor Energy Terra Nova riser replacement programme were shown to leak during field tests performed after site installation. No hydrocarbon loss occurred nor was there an environmental incident; however, the scheduled production start-up for the pipes was delayed. The pipes were designed and manufactured to comply with API [1] code and had successfully undergone full-scale factory acceptance testing (FAT) at 1.5 times design pressure following manufacture. Investigations confirmed that the leaks in both pipes occurred due to a crack in the polymer (PVDF) barrier within the end-fitting region of the pipe. It was also concluded that the crack in the barrier in these pipes occurred after completion of the FAT and sometime during the transportation, storage and subsequent installation of the pipes in the field. It was identified that the problem in the barrier resulted from an unknown thermo-mechanical loading condition of the pipe during this period, and also related to specific design features of some components in those end-fittings. The TapRoot Root Cause Analysis (RCA) tool was used to guide the investigation effort and consider all available data. Small and full-scale tests were performed to simulate and understand the end fitting design in the environments and conditions experienced during transport, installation and offshore testing. What is presented here is a brief outline of the incident and details of the subsequent investigation. The investigation was conducted over a period of 18 months with the participation of all parties involved in the design, manufacture, installation and operation of the flexibles. This paper summarises the investigation process followed, documents the results, discusses the results and outlines the conclusions and recommendations arising from this investigation.