Echo Yodel Decommissioning Study

Benefits

Expertise in subsea pipeline, umbilical, and structure stability, internal and external corrosion, hydrodynamic processes, seabed scour, pipeline self burial, and integrity management of subsea systems, enabled Atteris to successfully develop well-informed degradation timelines to support the proposed in-situ decommissioning of the Echo Yodel pipeline and umbilical. Chemical engineering capabilities in the subsea environment meant Atteris was able to define a robust mercury removal and disposal strategy. The deliverables executed by Atteris provided guidance to the operator on developing the most environmentally, economically and safe methodology for the proposed decommissioning.

Background

The Echo Yodel (EY) fields operated by Woodside Energy Ltd (WEL) are located 120 km NW off the coast of Dampier in Western Australia in approximately 130 m water. Production from the fields was processed on the Goodwyn Alpha Platform (GWA). Having been commissioned in 2001, EY reached the end of its economic production life in H1 2012 and subsequently ceased operations. Planning for decommission of the pipeline, umbilical, and associated structures required assessment. As part of that process, understanding the degradation timeline for an in-situ decommissioning option was required.

Work Performed by Atteris

Semi-quantitative pipeline and umbilical degradation study – a timeline for degradation of the EY pipeline, umbilical and associated control system structures was developed assuming decommissioning in-situ. The investigation into the mechanisms and causes behind the degradation was achieved through a combination of engineering, reference to industry analogues and academic study.
Mercury removal and disposal methods – methods and technologies were identified and ranked on their ability to remove mercury as part of pipeline decommissioning operations should it be present.
Mercury removal execution feasibility study – a high level execution methodology for mercury decontamination of the EY pipeline was developed however later testing indicated no trace of Mercury.