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Deep-water pipeline innovations

06th August 2012

Production from deep-water and ultra-deepwater requires pipelines with high thermal insulation coatings and resistance to aggressive fluids. Innovation is crucial

X-Stream can significantly reduce the cost of deep-water and ultra-deepwater pipelines and stay within stringent safety and integrity boundaries

As oil consistently trades north of USD 80 per barrel and with natural gas coming more to the fore, a good deal of the easily accessible supplies are gone or dwindling. Production from the hard to reach places, such as deep-water, will increasingly become the norm. For that to happen, pipeline technology has to innovate for the environment where a diver simply cannot go. 

X-Stream pipeline for extreme environments

Norwegian independent foundation, DNV says that it has developed a new pipeline concept. It claims its so-called ‘X-Stream’ system can significantly reduce the cost of deep-water and ultra-deepwater pipelines and stay within stringent safety and integrity boundaries. The foundation, which says that 65 per cent of the world’s offshore pipelines are designed to its standards, believes that using X-Stream means a reduction in the pipeline thickness, welding time and installation when compared to current deep-water pipelines.

“Typically, for a gas pipeline in water depths of 2,500m, the wall thickness reduction can be 25 to 30 per cent compared to traditional designs,” according to DNV. Dr. Henrik O. Madsen, DNV’s CEO. Deep-water gas transportation market will “experience massive investments and considerable growth over the coming years,” he said adding: “new safe and cost-efficient solutions are needed.”

X-Stream technology

By constantly controlling the external and internal pressure differential of the pipeline the amount of steel, and therefore the thickness of the pipe wall, can be reduced by up to 30 per cent and perhaps more depending on the product, making manufacturing cheaper installation easier and less expensive, believes DNV. The foundation’s engineers led by DNV in Rio de Janeiro, Brazil utilised and inverted a high pressure protection system (i-HIPPS) and inverted double block and bleed valves (i-DBB) that will immediately isolate the deep-water pressure in the event of a pressure failure so that the internal pipeline pressure can be maintained above the critical level. During the installation process the pipeline is fully or partially flooded to control the differential pressure, while the i-HIPPS and i-DBB systems ensure that pressure never falls below the collapse pressure, says DNV. Minimum pressure needs to be maintained during pre-commissioning too and DNV says that this is achieved by using produced gas separated from the water by a set of separation pigs and gel; an industry standard practice. X-Stream has just completed the innovation project phase and DNV says that it intends to continue to work with industry on refining and testing.

Mechanically lined pipelines in action

Aberdeen based Subsea 7 has already been working with German group BUTTING to install its  mechanically lined BuBi lined pipe for production from ever deeper and more corrosive reservoirs. Together the two companies have developed a technology deemed by DNV to be, “fit for service,” to allow the successful reeling of the mechanically lined pipe without affecting the performance of the BuBi lined product. “The exploration and production of deeper and more corrosive subsea reservoirs demands that we design more subsea infrastructures and pipelines to cope with increasing amounts of carbon dioxide and/or hydrogen sulphide. Our solution, using the mechanically lined pipe (BuBi lined pipe) with BUTTING by reel-lay, offers a cost effective solution to transporting corrosive fluids,” said Stuart N Smith, Subsea 7 VP technology and asset development.

Tried and tested

The companies say they have established a methodology for the full installation sequence and pipe samples have been fatigue tested in the post reeled condition. The results indicated that the BuBi lined pipe suffered no detrimental impact from the reeling and testing and could be reliably used under existing practices. Qualification of the technology led to the award of Guará-Lula NE contract by Petrobras in 2011, which Subsea 7 says included the reel-lay installation of several BuBi pipe steel catenary risers in a water depth of 2,100m. “Technological developments and how we apply them to clients’ projects are crucial. We aligned with BUTTING and have developed together a world class product that can be used in some of the most demanding environments, from the North Sea to Brazil,” said John Mair, Subsea 7 global technology director.

Subsea tapping machine unveiled

Operating primarily out of Stavanger, Norway the offshore arm of T.D. Williamson Inc., TDW Offshore Services (TDW), has developed and now deployed in the field its Subsea 1200RC tapping machine. The lightweight, remote controlled system means that hot tapping can be carried out from a diving support vessel (DSV) in shallow water and also at depths of up to 3,000 metres. “The most critical part of the hot tapping process is the point at which the drill penetrates the pipe,” said Mike Benjamin, TDW’s vice president, offshore pipeline solutions for TDW in a statement. “The direct control and visibility from a laptop will revolutionise hot tapping, giving way to a more efficient and safer process.”

Field tested

TDW says that the system has already been successfully tested in relatively shallow water (91m) and aside from the safety benefits the company says the new technology “offers total control and visibility of the tapping operation where there was none before. Built-in sensors allow continuous recording of actual pressures, temperatures, rotation and movement of the pilot drill and cutter.” Operated from a programme on a laptop computer, the end result of the hot tapping operation results in accurate and quality operations, believes TDW.

Other benefits

Other benefits highlighted by TDW for the Subsea 1200RC tapping machine include easier handling because of its weight and no pipeline shutdowns because the system works without disrupting the flow of the pipeline during routine maintenance or in the event of an emergency shutdown. Furthermore, when the system is required for tapping into existing subsea tees the company says there is no requirement for a hot tap fitting as the system can be deployed and hooked up to the isolation valve with a mechanical connector. In particular, TDW considers that its hot tapping system will prove especially useful for the emergency pipeline repair system (EPRS) programmes that it offers to its customers. 

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