Flexible pipes are more and more used due to their unique performances, their high versatility and their economic efficiency. In addition, the development of deep water fields and of Floating Production and Storage Offloading (FPSO) technologies will increase their uses. The composite structure of flexible pipes, the mechanical conditions of the different layers as well as the chemistry of the environment lead to very specific working conditions. To increase the performances of these products, intensive research programs have been conducted in the last five years to determine the actual operating conditions of the metallic materials in the annulus, particularly in sour service applications. After a short presentation of the product, the paper presents the experimental results and the proposed validated modelisation of the annulus environment versus the flexible structure and the bore composition. Specific aspects of corrosion and electrochemistry in confined environments are presented. The mechanical, metallurgical and corrosion behaviour of the high strength metallic components specifically developed for these applications are presented, particularly in term of microstructure, corrosion and SSCC/HIC behavior in sour conditions.
Keywords: flexible pipe, annulus composition, permeation model, corrosion, confined environment, induced cracking, sulphide stress corrosion cracking. hydrogen