Cliff Head Pipeline Span Rectification


Roc Oil is extending the life of their subsea pipeline assets as part of the Cliff Head development located in the Perth Basin, Western Australia.  The life extension program required survey and assessment of the pipelines for stability and free spanning. The metocean data for the area had also been revised.

Work Performed by Atteris

Atteris conducted a Level 2 Span Assessment of the pipelines. This included a thorough rationalisation of through life survey datasets to determine span configurations and determine behavioural trends of spans over the life of the asset and these in to the future for remaining. Allowable span lengths were re‑calculated based on the revise metocean data and the fatigue life of critical spans was assessed. Sensitivity analysis to marine growth was also performed. A number of spans were identified for rectification.

Project management was provided on an as-needed basis to scope and tender the rectification works. Novel subsea rock installation methods were identified from previous experience that allowed cost effective rectification whilst ensuring pipeline integrity. FEA analysis of dropped object scenarios was used to assess the risk of a loss of containment event.


Integration of the Atteris engineering design team with the Client’s execution team led to efficiencies in communication, delivery, and a reduction in project cost, risk, and schedule. Optimised span rectification scope and support managing the tender process allowed a direct cost saving of  up to AUD 500,000 (40% reduction). Engineering also demonstrated that a shutdown was not required during installation, streamlined environmental approvals, and avoid the requirement for oil spill modelling.