The Hybrid Composite Flexible Pipe: A New Generation of Flexible Pipe and a Definitive Solution for High CO2 Content Applications

Abstract

Abstract The paper aims at presenting the extensive qualification approach adopted for the Hybrid Composite Flexible Pipe (HFP). The test results presented are mainly focused on the capacity of the PEEK-Carbon Fiber composite material and the pipe to resist to harsh environment, which combines high CO2 content, high pressure, and temperature, demonstrating that HFP is a Stress Corrosion Cracking (SCC) resistant solution in ultra-deep-water environments. The extensive testing campaign leveraged the classical pyramid approach described in DNV standard RP-A203, starting with material small scale to conclude on product full scale tests. The models developed aims at bridging the gaps from the idealized material level to full scale level. A comprehensive description of the testing done at the different scales to qualify the product for the most aggressive environments is given, including innovative methodology for end-of-life characterization for both material and the full-scale levels. Results of correlation between the experimental full scale prototypes tests and models are also provided. At material scale level, a first step called fluid screening was conducted, aiming at identifying the most detrimental fluid to be conservatively used for all the subsequent small-scale testing campaign. The most significant finding is that the PEEK-CF composite material is inert to high contents of H2S. Additionally, there is no ageing of the material exposed to fluids with large CO2-content, demonstrating a good resistance and stability in CO2-rich environments. Results of the long-term properties measurement (fatigue and stress-rupture mainly) under continuous presence of high CO2-content fluid combined with high pressure and temperature, are also discussed. The permeation testing campaign revealed excellent permeation properties leading to a dramatic drop of CO2 partial pressure in the tensile armor wires annulus compared to conventional flexible pipe, making HFP a definitive SCC-free solution. Additionally, results of HFP full-scale tests done after months of CO2 saturation at high pressure and temperature have demonstrated a very good stability and behavior of the product over time. Finally, the paper presents the calculation model developed and compares it against the tests done at the medium scale and HFP full-scale levels, showing a very good correlation. The Hybrid Composite Flexible Pipe is a breakthrough technology combining the best composite material and the conventional flexible pipes. The novelty of HFP lies in the ability to solve sustainably the SCC challenge, observed on conventional flexible pipes, for a service life of 30 years, allowing the safe use of this step-change flexible pipe technology in harsh and CO2-rich environments.