Abstract

Tough market conditions have seen the price of oil drop by circa 50% between mid 2014 and early 2015. This drop and subsequent uncertainty have seen the oil and gas industry concentrate on the cost of designing, installing and operating pipelines. A critical process for the industry is the procurement, manufacture and installation of appropriate linepipe. The method of installation is often dictated by the pipe size and the water depth that the pipe is to be laid in, however there are times when the choice of lay method is due to vessel availability and relative costs for each technique.

The industry regularly uses seamless pipe for installations by reel lay, however submerged arc welded linepipe (SAWL) has successfully been manufactured, installed and commissioned via this method and can realise significant cost reductions. SAWL material installed via the reel lay method has not been fully characterised to understand the material properties during the installation process and no formal characterisation program was undertaken for the successfully installed projects. To combat this lack of knowledge a technology qualification following the basic principles of DNV-RP-A203 was carried out to research the strain behaviour of pipes intended for reel-lay installation.

This paper outlines the technology qualification process used to characterise the behaviour of a 406.4mm OD × 22.2mm WT SAWL linepipe material that was subjected to full scale reeling simulation using a fixed end cantilever type reeling simulator. A comprehensive test program was developed and carried out to provide the characterisation of the linepipe base material and longitudinal weld, both before and after full scale simulated straining and ageing. The test program was set up to prove the material properties against DNV-OS-F101 Supplementary Requirement P and the results of these tests are presented hereafter.

The work presented in this paper will provide a basis for future investigations into the strain behaviour of pipes of different sizes and wall thicknesses or different straining cycles intended for reel-lay installation.

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