Localised assessment of pipeline integrity during ultra-deep S-lay installation

• The installation of pipelines in ultra-deep waters addressed.
• Detailed local finite element model used to predict residual curvature and pipe roll.
• Numerous installation scenarios considered.
• Comparisons made with output from commercial global analysis methods.

As offshore oil and gas developments move into ultra-deep water depths, the greater the impact onerous installation procedures will have on pipeline integrity. Current approaches for predicting this impact are mostly based on a global pipeline perspective, using installation analysis tools that model the entire length of suspended pipeline using a string of ‘pipe’ finite elements. While these analysis methods are proven to provide reasonable predictions for moderate installation loadings, they lack sufficient detail for considering the most extreme conditions and do not generally account for material plasticity, residual curvature and pipe twist. This lack of detail could represent a significant shortcoming in future developments where pipe joints will be subjected to more substantial loading during ultra-deep water installation. A detailed local finite element model of the pipe cross-section during installation has been developed that allows for greater insight into the actual as-laid condition of a given pipeline. Numerous installation scenarios are considered and comparisons are made with output from traditional global analysis methods. These comparisons demonstrate potential shortcomings of existing engineering design approaches for ultra-deep water. This ultimately leads to recommendations that will shape on-going developments in design methods.