The qualification of a pipeline system for hydrogen transport, even if strictly related to offshore pipelines, is a broad field that requires a systematic approach from basic material knowledge to complex physical models, fracture, and fatigue assessments. The combination of embrittlement with the severe loads of an offshore pipeline calls for a comprehensive awareness of material performance under such conditions. To achieve that, the first step has been the classification of failure modes by type of installation condition and selection of the tests required to characterize materials against them. A second step was to strengthen the state-of-the-art knowledge on data and tests availability for such failure modes. A third step was to set up and conduct a dedicated testing campaign focusing on girth welds and develop a pipeline system qualification procedure. The technological and standardizations gaps, identified in the design, construction and installation process chain are described, along with the actions taken by an offshore EPCI contractor to overcome and fix them. The analysis of qualification requirements, including available test types and testing protocols, led to a matrix of potential tests to be done in hydrogen and air environment for the steel base material, seam weld and girth weld of offshore pipelines. The final design of the test campaign included the minimum number of key tests necessary to assess the effect of atomic hydrogen inside the steel matrix and the related changes in mechanical properties, including the evaluation of tensile behavior and ductility, impact properties, fracture toughness (through KIH and rising load tests) and the critical soaking time in H2 environment. The tests were performed in different concentrations of hydrogen (i.e., different blending scenarios) at a given pressure which was considered potentially representative of the future main operating conditions in offshore hydrogen transportation systems. The main findings of the R&D work presented in the paper confirm that the qualification approach should include material properties testing under various conditions to support and provide a strong and sound scientific basis for the standardization process of the offshore EPCI pipeline system. The new tests and test conditions concur to complete the knowledge on the materials suitability for transporting hydrogen and hydrogen blends in offshore pipelines.

This paper reports the Lessons Learned from an innovative linepipe solution that was successfully implemented on P55 Deepwater Project. The P55 field is located offshore Brazil, in the northern area of Campos Basin, in a water depth ranging from 1500m to 1900m. The scope of work consisted in engineering, procuring, fabricating and installing 16 rigid Steel Catenary Risers (SCRs), which are the first of their kind in this area. The corresponding 12-inch SCR qualification results are presented in the perspective to show the significant benefits of the technology used and its potential developments to High Pressure & High Temperature applications.In order to meet tight Hi-Lo requirements together with high fatigue performances, innovative Pipe End Design and associated automatic welding procedures were developed and qualified. The paper describes the complete sequence of pipe manufacturing process, from hot-rolling to final machining, which resulted in a concentric and reproducible pipe end geometry, ideal for limiting Stress Concentration Factors.An extensive qualification program of Full Scale Fatigue test was conducted on girth-welded strings and the associated results showed performance levels at least four times above the target curve. Moreover, Lessons Learned from the offshore campaign established that developed Pipe End Design led to significant improvements in welding times and subsequent J-laying rates. Details on how the technology effectively reduces critical times and lowers rejection rates are provided on the basis of the actual P55 offshore campaign.In addition to the advantages detailed in the paper, the presented linepipe solution proves to be also applicable to High Temperature fields, since the enhanced fatigue behavior was found to compensate a temperature derating up to 270°C. In fact, the presented manufacturing and welding technologies have opened the perspective of ongoing Developments, which are believed to bring a reliable solution for combined High Pressure and High Temperature applications.