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Brazil riser inspection study turning up results

The 1% royalty levy that Brazil uses to fund oil and gas research and development, applied in circumstances where leading operators are working together to solve pre-salt challenges, is starting to produce some interesting new developments, writes Gareth Chetwynd.

A key area of research for Petrobras, Shell and other partners in the first phase of pre-salt development is the issue of riser inspection due to the discovery of stress-induced corrosion cracking on flexible gas risers in the Lula and Sapinhoa pre-salt fields.

High levels of carbon dioxide in the associated gas triggered flooding of the annular section of the risers, severely weakening the structures.

Petrobras ordered inspections and developed mitigation measures but Upstream understands that other cases of annular flooding have been found.

The problem has created an expensive demand for riser inspection on the first generation of floating production, storage and offloading units working on these fields, and is likely to reduce the field life of some of the risers.

Petrobras has moved to contract specialised technical services for shallow-water intervention, but Upstream understands that the operator is unable to carry out adequate inspections of the interior state of flexible risers in deep waters.

“Beyond 600 metres, it is a case of stopping production on the riser you want to inspect and pulling it in,” one consortium source said.

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This problem has spurred Petrobras to work with partners such as Shell and Galp Energia on new riser inspection technologies.

Shell also has its own riser inspection research programme, building on R&D work that the company has been funding through the Senai Cimatec training and research facility on the Federal University of Bahia (UFBA) in Salvador.

A flagship project there is an autonomous underwater vehicle (AUV) technology called FlatFish, designed to carry out detailed inspections of subsea pipelines and structures.

The FlatFish technology has multi-modal sensors and allows visual inspection in 2K-resolution 3D. Artificial intelligence and subsea docking capability means operators can dispense with the need for the support vessels normally used for the deployment of conventional remotely operated vehicles.

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Automatic inspection technologies using high-quality 3D reconstruction can detect faults that a human might miss using infrared or ultraviolet sensors.

The German Research Centre for Artificial Intelligence (DFKI) is also a partner of Senai Cimatec and the first prototype was built and tank-tested in Bremen, Germany, with participation of several young Brazilian researchers who then went back to Salvador to build a second prototype, made from titanium and plastic composites and described as lightweight but robust.

Testing moved to a sea environment in the sheltered waters of Bahia’s All Saints Bay.

FlatFish started as what is essentially a data-gathering vehicle, but it can serve as a stepping stone to even more advanced AUVs that can take on more proactive inspection tasks, such as measuring corrosion, or even tackle some intervention and manipulation work, such as opening or closing valves.

The project is now in its second phase, which involves third-party commercialisation and construction of a full-scale vehicle.

“We went to a certain point and we now have a company working on a deep-water vision, using the same software we developed, and it will be ready for its first tests next year,” says Rosane Zagatti, subsea and topsides technology manager with Shell’s Brazilian unit.

Shell has also been carrying out studies of riser fatigue in its own Bijupira Salema field, a mature development in the Campos basin.

FlatFish is just one of several projects where the pre-salt partners are trying to address the gap in the market for a deep-water tool able to inspect the interior of risers for integrity monitoring and life extension.

“Corrosion cracking is one of the key problems for us to solve. Some of the risers are in the limit of their use. We are working with industry to solve this problem,” says Andre Cordeiro, a Petrobras manager who mentioned the company’s own MODA project, aimed at monitoring the integrity of flexible risers.

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