Self-standing hybrid riser in Roncador debut
  from: Offshore Engineer
  by: Jennifer Pallanich
  Monday, April 21, 2008

With the installation of a self-standing hybrid riser on Petrobras’ Roncador field, the first of four deepwater production solutions specifically targeted under Brazil’s Procap 3000 initiative has become a reality. The other three evolving technologies are slated for deployment by 2010. Jennifer Pallanich reports.

Improving fatigue life of risers in Brazil’s deepwater has been one of the aims of Procap 3000 since its inception in 2000 as the technological capability program for deepwater and ultradeepwater exploitation systems for Petrobras.

.The Brazilian operator’s Cenpes R&D;facility in Rio de Janeiro believes Procap has achieved that goal with its selfstanding hybrid riser (RHAS).

The first RHAS was installed last October in the Roncador field in 1800m of water to export from the P-52 semisubmersible floating production platform. According to Procap coordinator Mauricio Werneck, the system is designed for a minimum of 20 years’ operation. A 35m floating cylinder about 170m below sea level holds the top of the long steel vertical riser which is connected to the FPU via a flexible riser.

‘The main point of this technology is to separate the movement of the floating unit from the steel riser,’ explains Werneck, noting that doing so improves the fatigue life of the rigid riser. ‘This is a problem we’ve been facing for too long. If we need to install an SCR, we’ve always had this problem.’

Procap is concentrating its activities on risers for very deep waters and large diameters for high production wells as well as subsea processing and pumping systems to improve the flow from Petrobras’ existing and new marginal fields, he says.

The first installation of selfstanding hybrid riser technology exports production from P-52. Werneck says the team discussed steel catenary risers as a P-52 well production solution but deemed the flexible riser to be a more attractive option. The self-standing technology can also be used for collecting, but in a bundle configuration, instead of a single pipe as in the export system, he adds.

‘But we’re working with different concepts for the collection part of the fields to hang different rigid risers from the wells to the units.

‘One of the options is a subsea buoy that will be located also below the sea surface and connected to the floating unit via flexible jumpers.We have no projects right now for other installations with the RHAS technology, but certainly it will be considered for the next deepwater units,’ he says.

The size of the riser meant finding a powerful laying vessel in a tight market. ‘It’s not every vessel that’s able to lay large diameter pipe, in this case 18in diameter, in 1800m of water,’ notes Werneck.

Technip’s Deep Blue was assigned the job and, following an installation plan proposed by Technip, finished installing the riser at the end of October 2007. Strong winds and high seas were anticipated during installation, but in the event the operation was performed ‘without any problem’, reports Werneck.

According to Werneck, the RHAS is suitable for areas where rigid risers or flexible risers for a large diameter are not yet available. ‘If we have high water depths, probably we could use this kind of riser. The only problem is they only take care of one riser at a time. It is a good solution for the export system.

‘This is one more tool we can use in this very challenging environment,’ he adds.

Meanwhile, in other areas, Procap is working on subsea processing systems and boosting systems ‘to improve the way we deal with our subsea fields, mostly the mature ones,’ says Werneck.

Petrobras has installed some Schlumberger and Baker Hughes Centrilift electric submersible pumping systems.

‘We have some seabed boosting systems and also pumps installed inside the subsea wells,’Werneck says.

Procap is finalizing development work on the SBMS 500, a 500m3/h subsea multiphase pumping system rated for water depths to 1000m. ‘It’s a system that we’ve been working on for a long time,’ says Werneck, pointing out that some equipment was damaged during the initial installation and had to be sent back to the supplier for repair.With that repair work nearing completion, he expects the system to be reinstalled in the front half of 2008 in about 800m of water in the Marlim field.

Another important technology is a raw water injection system that collects seawater near the wellhead, roughly filters it and injects it into the reservoir. ‘We only connect from the floating unit to this system an umbilical that provides power to the pump and some chemicals that help this system to control problems related to the seawater injection,’ explains Werneck. ‘Some of our units don’t have spare capacity in terms of treating seawater to inject in the reservoir to keep the reservoir pressure. Having the system subsea, you can have the seawater injected without any construction topsides.’

Petrobras is targeting the Albacora field in 2009 for first installation of this technology.

Another pet Procap project is a processing system for oil and water separation for viscous oils that have a tendency to form steady emulsions. Werneck says he expects that system to be available from 2010.

‘To break emulsions and separate the water is a very challenging task,’ he explains. In separating the oil from the water, Petrobras wants to ensure the system keeps pressure as high as possible to keep the gas soluble in the water. Another step involves injecting chemicals to help break the emulsions. By injecting through the christmas tree or through gas lift to the well, says Werneck, the chemicals will have more time to react along the flow of the production stream.

‘We have two problems – emulsions are very steady and the system is very compact,’ which means the fluids will run through the system more quickly, he says. The current focus is on chemicals to help break the emulsion. A related effort is a monitoring system to keep operations performing optimally.

Petrobras is looking to obviate the need for a large installation vessel when the first of these separation systems is deployed in approaching 1000m of water. Therefore,Werneck says, the system development emphasis is on compactness while at the same time maintaining good processing capacity.OE

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