After 8 years of preparation, the day came and went swimmingly. Maureen, the biggest fixed platform in the North Sea to be moved, has risen from the deep and refloated.

It is residing in a new home for retired North Sea installations...in this case, Aker Stord in Norway, after a 3-day, 165-mile (265-km) tow. Here, the huge platform, weighing in at a majestic 110,000 tonnes, will be moored in deep water in Digernes Sound, to await a decision about its future. Each day, however, the facility is gradually deteriorating, and the cost of keeping it there climbing.
Realistically, Maureen's owners, including (former) field operator Phillips Petroleum, have until the end of the year to find a buyer for the facility, break it up and sell bits and pieces or recycle the whole structure. But that's some way off just yet.
Total costs for the project are in the region of US $225 million (£150 million), which includes contracts for all work up to July, incorporating work carried out by the refloat contractor, Aker Offshore Partner. Within that total is at least $16.5 million (£11 million) spent on studying how to go about the operation and investigating the technologies involved.
Refloating was a carefully planned and precise operation that reached its climax at 5 p.m., June 26, when the huge steel and concrete-base structure slowly broke free of the seabed, where it had been held in place since 1983.
The giant came to the surface slowly in 60 hours after water was injected under the platform to create power for an upward lift. Seawater was simultaneously pumped out of the platform's three concrete tanks, deballasting them, and the water was replaced with inert nitrogen gas to achieve neutral buoyancy.
Phillips said the operation was carried out in a "safe and controlled manner."
Before it all happened though, decommissioning project manager Andy Halliwell revealed considerable thought and planning went into several unwanted possibilities. "We have a number of contingencies that we have worked through with Aker if it does not go according to plan," Halliwell said, just a couple of weeks before the big day. "One of the first is whether additional buoyancy (is needed)." Arrangements were made to ensure additional buoyancy was available if required.
Another issue was a means of providing more water power underneath the platform should it fail to rise naturally under neutral buoyancy. To offset this risk, a soil surcharge was put in place around the skirts of the three tanks.
This seal - comprising gravel and iron ore - was put in place last year after an investigation by Fugro revealed the existing soil structure below the platform would not be able to contain sufficient water pressure necessary to allow the platform to break free from the seabed.
Inclinometers were installed on the structure so engineers could instantly detect any movement outside acceptable parameters. "The platform can tolerate 22° of tilt," Halliwell said.
Pressures inside the storage tanks were constantly measured, to monitor unacceptable variations. And the rate of ascent of the vast structure during the refloat also was minutely measured - down to the millimeter.
However none of this is groundbreaking; it was done in reverse 18 years ago when the platform was installed.
"When the platform came out, it survived a force 10 gale," the project manager said, with just a touch of pride, "so we know it can cope with that."
Now that the question of refloating the facility has been answered, some still tougher issues face the field partners. Phillips and its partners have to pay to keep Maureen in Norway. The facility will be cleaned, and all barnacles and other marine debris will be removed from the steelwork and concrete tanks. But that will cost, and renting mooring space will cost as well. Maureen will have to be maintained in good condition unless and until a reuse option is identified.
But the chances of that happening are slim. Phillips has been marketing Maureen for years, trying to find a suitable buyer on the Internet through the services of Dutch-based Web Platform Brokers. Phillips staff traveled to China to try and identify a suitable project in Asia.
Projects worldwide, in which either Phillips or any of its partners have been involved, have been trawled for their suitability to reuse Maureen. So far, however, that process has not met with success.
Halliwell admitted, "We do not have a reuse option." While that is the most desirable option - and the one that makes the most economic sense - it just doesn't look likely at this late stage. "We are still talking to some people," he said.
Partial reuse is under consideration, and that includes civil engineering projects such as quays and bridges. (The infamous Brent spar ended up as the foundation for a new quayside at Mekjarvik, Norway.) And in the worst-case scenario, "deconstruction" of the facility and recycling of up to 95% of it has to be brought into the equation too. "We expect by the end of the year we will be making a choice between one or the other."
Now that the platform is out of the way, several other field facilities still on the seabed in the UK North Sea's Block 16/29b have to be dealt with:
• Maureen's articulated loading column used to offload crude to shuttle tankers that was refloated and taken to Aker Stord;
• a 1.5-mile (2.3-km) pipeline from the platform to the loading column that is buried and being left in place after cleaning;
• the single-well Moira satellite 6.2 miles (10 km) from the platform and its associated pipelines, umbilicals, wellhead, production tree and protection structure (these already have been removed ashore); and
• the drilling template beneath the platform, also destined for total removal.
Keeping it green
Drill cuttings below the platform are to be left in place since Phillips is not satisfied that any suitable alternative disposal option would reduce the environmental impact of the cuttings further. The cuttings pile is no higher than 4 ft (1.3 m). Physical and chemical degradation has taken place on the pile since it started to accumulate, lessening its impact on the seabed. At the same time, Maureen partners have been involved in industrywide studies on the impact of drill cuttings piles on the seabed and efforts to find environmentally friendly disposal options for them. Phillips has separately studied the cuttings pile at Maureen, and although the pile contains drilling mud - comprising kerosene and synthetic oils - it said the pile will be monitored as part of a post-decommissioning program.
Acutely aware of the environmental sensitivities surrounding this project, Phillips went beyond what was required under applicable regulations and shipped all the liquids used to clean the storage tanks ashore rather than discharge them into the sea. A licensed onshore disposal facility was used. Also, when the refloat took place, seawater inside the tanks was offloaded to a tanker for onshore disposal.
Field development
Discovered in 1973, the Maureen field was the first oil development by Phillips Petroleum in the UK offshore sector. At that time, Phillips was aiming to become a major North Sea player. So the platform was designed to be reused once other, equally big fields were found. These finds never materialized, but the platform was unique in its design for refloatation. It was built at Hunterston, Scotland, and the production deck and base were mated together at Loch Kishorn prior to installation at the field in 1983. Maureen came onstream in September that year and achieved peak output of 78,000 b/d of oil in 1985. Production ceased in 1999 after the extraction of 220 million bbl of oil and the field was depleted. Production had fallen to around 5,000 b/d of oil, and it was no longer economic. The field takes its name from the wife of the Phillips Petroleum geologist who helped discover the reservoir.
Since planning for decommissioning started in 1993, 93 legal permits had to be obtained for project clearance. About 300 people or organizations have had to be consulted, and Phillips Petroleum has made a huge effort to keep people - including the media - informed of progress on the project. This has even included a Maureen Web site.
After the refloat, Henry McGee, president of Phillips' European division, was clearly pleased with the work that had been accomplished. "Today our engineers have demonstrated that Phillips' reputation for innovative excellence is well founded," he said. "Our decommissioning project team and our refloat contractor, Aker Offshore Partner, have done a superb job in executing this complex operation safely, efficiently and in an environmentally sensitive manner."

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