The purpose of this study is to evaluate the effectiveness in the contribution of the interpass welding in the microstructures and properties of the dissimilar fusion zones produced with an alloy 625 and API 5L X65 steel pipes. Three multipass welded joints with v-groove, were made under the same welding parameters, therefore, changing only the interpass temperatures at: 150°C, 250°C and 450°C. The microstructural characterization was performed using the light microscopy and the scanning electron microscopy (SEM). The hardness test, charpy-V impact test and the transverse tensile test were conducted according to specific standards. The results have shown that all ruptures in the tensile tests occurred in the base metal. Both yield strengths and ultimate tensile strengths, have dropped to the 450°C interpass temperature. It was also observed a slight drop in the hardness with increasing interpass temperature. The Charpy-V impact test results showed no significant differences among the interpass temperatures. These said results indicated that the maximum interpass temperature for the alloy 625/X65 steel dissimilar welding is limited by the steel properties.

This work evaluated the hydrogen embrittlement resistance of the nickel-based UNS N08830 alloy through a hydrogen charging study, slow strain rate (SSR), and fracture toughness tests. The microstructure evaluation showed large-size austenitic grains with no evidence of second phase precipitation, a high fraction of low-angle grain boundaries, and texture of {100} and {111} planes in the rolling direction. From SSR tests results, strain to fracture and reduction of area embrittlement indexes of 25.3 and 42.1% were found, respectively. A modest drop in fracture toughness of approximately 20% was observed. From fractography, it was observed a prevailing mixed micromechanism of fracture comprised of microvoids coalescence and quasi-cleavage flat facets in secondary cracks aligned with the rolling direction. The quasi-cleavage flat facets showed nanovoids at the slip line intersections, which in turn confirmed Hydrogen-Enhanced Localized Plasticity (HELP) as the prominent embrittlement mechanism. Because of the material's crystallographic texture, a good part of hydrogen was not transported to a direction normal to the applied stress as it would happen for pure diffusion but instead followed the dislocations in the rolling direction. That effect caused that less hydrogen was concentrated in the main crack tip, which inevitably increased the overall energy for fracture.

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This paper presents a set of technologies and optimizations implemented in the All Electric FPSO, the largest PETROBRAS’ design, that was conceived to operate in Atapu and Sépia fields and will become into P-84 and P-85 FPSOs, respectively. This design was done to increase the Pre-Salt production, add more value to its reserves and minimize greenhouse gas (GHG) emissions. All Electric concept considers all rotating process equipment to be driven by electrical motors. Based on this concept, the process plant configuration and the number of equipment trains were defined to comply with the flow capacities. The adoption of this new concept was possible due to proactive advocacy of PETROBRAS and other oil and gas companies for the revision of an environmental regulation that limited its use (CONAMA 382/2006). Moreover, other decarbonization solutions were selected and incorporated on the project based on MACC methodology and PETROBRAS's low carbon strategy. Considering the typical emissions of a FPSO, the technologies and optimizations were deployed on the main sources: power generation, flaring, venting and fugitives. Some reduction emission initiatives were implemented for the first time in a FPSO of large capacity, such as: all-electric plant concept, deeper seawater intake system, cargo tanks gas blanketing and recovery system and variable speed control on water injection pumps. Moreover, known technologies such as flare gas recovery system, closed drainage gas recovery system, cogeneration, low fugitive emission valves, and CCUS-EOR etc. were also used on All Electric FPSO design. As a result, the GHG emission intensity achieved was estimated about up to 30% less than previous FPSO designs. Another accomplishment was the zero routine flaring and venting, based on World Bank initiative, which PETROBRAS is committed. Finally, all these initiatives are significant to the company achieve its goals, maximizing value and producing oil and gas with reduction of GHG emissions. The All Electric FPSO design is an example of how an energy efficiency approach could achieve a reduction in GHG emissions. The lessons learned during the development of this design contribute to broaden the knowledge for oil and gas industry decarbonization.

High strength steels have large applicability in the gas and oil industry and are often used in aggressive environments, requiring the use of cathodic protection, with the consequent generation of atomic hydrogen in the cathode that may lead to hydrogen embrittlement, HE. The aim of this work was to evaluate the fracture toughness and HE susceptibility of two high strength steels, named as 38CrMo4 and 30CrMo6, used as components for oil extraction from the seabed. J-Δa curves for JIC evaluation were carried out following the ASTM E1820 [1] at room temperature in laboratorial air using C(T) specimen. For KTH evaluation the tests were based on NACE TM0177 standard [2], using sharply notched DCB specimens. For this test a 3.5 wt% NaCl aqueous solution with −1.2 V cathodic protection for the in-situ hydrogen charging were used. From the results it was observed that both steels presented predominantly martensitic/bainitic microstructures, with 30CrMo6 steel exhibiting lower mechanical strength and higher total elongation. The great microstructural differences rely mainly on the prior austenite grain size and in the S and Ca contents. 30CrMo6 steel presented a very fine prior austenite grain and mostly spherical CaS inclusions instead of the elongated MnS. These microstructural features lead to much higher KJIC value and it did not exhibit HE in the conditions analyzed here.