Flexible Pipe Integrity Management Strategies Applied to Lifetime Extension and Revitalization of Deepwater Brownfields

Abstract

Abstract The paper provides a new integrity management strategy for flexible pipes using state-of-the-art inspection and monitoring methods to gather data and a novel methodology to deal with ageing pipes that may already present some degree of damage to the tensile armor wires. The new process and integrity management methodology developed and applied to flexible pipes within Petrobras projects focused on tensile armor fatigue, enabling lifetime extension, reuse, and revitalization projects in brownfields. In order to optimize the lifetime extension process, the main failure modes for ageing flexible pipes were identified and R&D efforts were directed towards fast-tracking solutions for them. The focus was on developing tools to generate data and models to represent the end-of-life conditions of the flexible pipes. New analysis methods, based on full-scale testing of flexible pipes and years of in-field experience, were developed to better represent the behavior of ageing and damaged pipes. Years of data from full-scale fatigue testing (tension and tension and bending) have been used, with over 60 full-scale tests in the database, along with information from historical field failures, with over 70 dissections from pipes from operation, to calibrate fatigue calculations and additional models that can predict the behavior of flexible pipes with broken armor wires. These tools use both reliability-based and novel structural analysis methodologies to identify the limit state of the pipes and estimate a time-to-failure. Several inspection and monitoring tools were tested and developed to identify wire ruptures and provide valuable information to be used in riser integrity analysis. Various techniques have been developed to identify torsion through video imaging, however, they have limited applicability. The MODA (from the Portuguese of "Direct Optic Monitoring of the Wires") system provides information on the number of broken wires by directly measuring strain, however, retrofitting MODA may require outer sheath removal. The use of electromagnetic tools to evaluate wire strain has proven to be a reliable, albeit not as precise, method for investigating the state of wire integrity in existing pipes. The combination of the data gathered with the new tools and the new analysis methods, allowed a more detailed risk assessment and hundreds of pipes were able to have their life extended, enabling operation of ageing assets without significant CAPEX increase. With over 740 km of pipes operating in life extension, Petrobras was already able to add over 1000 years of service life to over 400 risers that are a key part of our long-lasting assets, with a special mention to one riser that has operated for over 46 years.