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The conditions to which flexible pipes are being exposed are becoming increasingly severe. In particular, flexible flowlines that are fully or partially restrained by back fill or rock cover can become exposed to large axial compression forces under pressure and temperature loading. A high True axial compression force may lead to a radial outward displacement of the tensile armour which could eventually exceed the allowable limits of API spec 17J if the axial force exceeds a critical level. Furthermore, when the net Effective axial compressive pipe force exceeds a critical level, the pipe may undergo global buckling either upwards (upheaval buckling) or laterally, which needs to be addressed in detail at design stage, typically by using global finite element (FE) simulations in which equivalent mechanical properties are applied to pipe beam elements to capture the overall behaviour of the flexible pipe. The overall global mechanical properties of a flexible pipe, such as axial stiffness and thermal and pressure expansion coefficients, which are important parameters in capturing the global buckling behaviour, are dependent on the local behaviour of the various flexible pipe layers. In this paper an advanced local FE model developed using the industry standard numerical FE tool, Abaqus, together with the assessment methodology is presented in order to study local layer interactions and their influence on the equivalent axial mechanical properties.

Abstract This paper presents the key findings from a significant, international joint industry initiative that took place over a period of about 20 months to September 2010. The SureFlex joint industry project (JIP) was run under the auspices of Oil & Gas UK and has had the financial support of twelve companies including operators, manufacturers and a legislative authority. The JIP has had technical contributions and provision of operational data from all the major operators of flexible pipe worldwide, flexible pipe manufacturers and flexible pipe specialists in the field. The JIP has produced two documents, namely i) a State-of-the-Art of Flexible Pipe Integrity, and ii) a Guidance Note on Flexible Pipe Integrity Assurance, and these documents are available publicly through Oil & Gas UK. The paper shows key findings from the extensive survey work performed including flexible pipe operational use worldwide, with statistics on design limits, damage and failure incidences. The paper summarises the latest inspection and monitoring techniques for flexible pipe and shows trends on how the technology is developing in this important segment. The paper very much addresses an important aspect of flexible pipe technology, subsea integrity, monitoring and inspection technologies, life extension and best practice integrity guidance for flexible pipe. Introduction In 2009 Oil and Gas UK decided that it was time to update a set of documents [1,2] that had been prepared some seven years earlier with regard to flexible pipe integrity. The focus of the earlier work had been on the use of flexible pipe mainly in the UK and Norwegian sectors of the North Sea; now it was decided that new work on flexible pipe integrity should be worldwide. After some effort, Oil and Gas UK engaged the financial support of twelve companies from around the world to perform a scope of work that would include the gathering of statistics on flexible pipe use, damage incidents and failures, the preparation of a report that would establish the current state-of-the-art on flexible integrity, and that would update the previous [2] Guidance Note on flexible pipe integrity assurance. This joint industry initiative (JIP) was coined SureFlex; the JIP was run under the auspices of Oil and Gas UK who subcontracted the performance of the work to MCS Kenny. The participants to the JIP included international oil company operators, a flexible pipe manufacturer and a regulatory authority. Over the twenty month period that the work was performed, MCS Kenny gleaned valuable input from the JIP participants as well as engaging companies outside of the JIP membership. Ultimately, the work has been performed with input from oil company operators, all the flexible pipe manufacturers and specialist flexible pipe consultancy companies from around the world. The JIP produced two deliverables, namely:A report on the current state-of-the-art on flexible pipe integrity, anda guidance note on flexible pipe integrity assurance. This paper provides a high level summary of the contents of these two documents and in doing so describes the key findings and recommendations from the work of the SureFlex JIP. State-of-the-Art Report The state-of-the-art report on flexible pipe integrity covers three broad areas as follows:Statistics of flexible pipe use, degradation, and damage and failure incidences during installation and operationCurrent practice on integrity management of flexible pipelines and risersCurrent and developing techniques for monitoring and inspection of flexible pipe