In mid-2005, GE's Oil & Gas PII Pipeline Solutions business faced a daunting yet familiar task when it was hired by Shell U.K. Limited  (Shell) to conduct an in-line inspection of its 452-kilometre “FLAGS”  (Far North Liquids and Associated Gas System) gas pipeline in the North Sea, off the Northeastern coast of Scotland. Commissioned in May 1982, FLAGS is located about 100 metres beneath the surface, running between the  Brent Bravo offshore production platform and a gas terminal near the village of St. Fergus, in Aberdeenshire.

In 2005, Shell sought proposals for an in-line inspection of the FLAGS pipeline. Shell’s engineers already knew the chosen vendor would have to address one particular problem inside the line: a 750-800 kilogram (1,650-1,760 lb.) clapper valve, which created a difficult obstacle for any smart tooling tool sent into the line. GE was asked to assess feasibility of negotiating the valve without requiring Shell’s intervention to lock it in the “open” position.

In mid-2005, Shell selected GE to conduct the inspection. According to GE’s North Sea project manager Mike Peterson, GE’s  expertise in dealing with such valves and other obstacles during pipeline inspections was a significant factor in the company's selection.

“The integrity of its FLAGS system is crucial to both (the operator) and the region,” Peterson said, noting 20-25% of the United Kingdom’s North Sea gas flows through this line at any given time. The project’s importance was underscored by the UK region’s heightening concerns about the need to enhance energy security. GE’s first challenge: devise a way to insert one of its four-metre long, magnetic flux leakage (MFL) intelligent tools into the (36’’) steel pipeline and complete the inspection despite the clapper valve. The second challenge: GE needed to complete the inspection without damaging either the valve or the inspection tool.

GE’s third, crucial planning concern would be to ensure sufficient battery capacity to cope with the entire 96-hour run time. After GE was awarded the contract, Mr. Peterson began working closely with his Shell counterparts — particularly Shell senior pipeline engineer Andy Studman and Steve Mayo from The Penspen Group, a London-based subcontractor for Shell and a former GE employee — to develop their final strategy.

For GE’s team, the chief priority was to figure out how to protect the tool’s inspection equipment by softening the impact of the tool’s collision with the valve, as the tool was traveling at about 1.3 metres per second.

“We needed to protect (the tool’s) primary sensor ring,” Peterson said. “Colliding with the clapper valve could damage both the valve and the tool, problems you want to avoid at all costs.” In addition, the launch trap on the offshore platform was vertical, which required additional tool modifications along with the use of a launch cassette.

Peterson began working on customizing an MFL tool with colleagues at GE’s Centre for Magnetic Flux Leakage Technology, located in Cramlington, England.

First, GE’s engineers removed the tool’s “buffer wheels” since the wheels could have been damaged in the collision. The engineers also managed to install additional battery modules to provide sufficient battery life to enable the tool to collect data during the entire 452-kilometre project.

Peterson also asked GE’s Cramlington group to design specially fabricated deflector discs, which were later installed around key components on the tool to provide maximum protection while allowing it to travel around bends in the line.

To further minimize any damage to the tool or the valve during the collision, GE engineers installed a series of aluminum buffers to the “nose” of the tool.

Their thinking was grounded in basic physics.

“Instead of a single point of impact (with the clapper valve), the idea was to spread the force of that impact across the entire front of the tool,” thus reducing the chances of damage occurring, Peterson said. GE also presented Shell with its “stuck tool/ no flow scenario” contingency plan, in which GE showed how it would configure the tool’s modules to allow gas to continue flowing around the tool in the event it became stuck in the line.

Initially, Shell also requested that GE create an on-land simulation of its proposed solution, but after GE provided the operator with computer assisted (CAD) modeling that demonstrated the soundness of its plans, Shell gave GE the green light to proceed with the inspection in February 2006.

However, GE had not yet finished encountering challenges above the surface. The team witnessed why the North Sea in February is never a sure thing, as it had to work through an intense snowstorm and other harsh weather conditions to deliver GE’s equipment to Shell’s Brent Bravo platform.

After being dispatched into the line March 17th, GE’s tool traveled about four kilometres without incident, before the moment of truth for GE’s and Shell’s engineers arrived — and passed — without incident, with the inspection tool successfully negotiating the valve section.  Now beyond its major obstacle, the tool continued gathering data for the entire pipeline and completed its inspection on the first run, on March 22nd. The tool’s data revealed no structural problems requiring immediate mitigation by Shell.

Peterson noted that the project’s “turn-around time” was another primary reason Shell selected GE, noting the final data analysis report was delivered to Shell in less than 30 days.  The pipeline operator later sent the GE team a note commending its team’s performance.

“In field, everything went exactly as we and Shell had expected when we originally developed our strategy for the project,” Peterson said.

For Shell, the inspection helped the operator further improve its monitoring of an important part of its gas pipeline network and enhance energy security for Western Europe. For GE, the project was the perfect opportunity to demonstrate its engineering expertise and project turn-around capabilities to an extremely important customer.

Brent Bravo is one of four Shell platforms located in Brent Field - a cornerstone of the UK’s oil and gas industry since its discovery in 1971 that is located about 500 km northeast of Aberdeen.

For more information, please contact:

Mike Peterson
michael.peterson@ge.com

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