Nonconcrete gravity-based platform refloated successfully

Aug. 6, 2001
Last June, the largest and heaviest nonconcrete structure in the North Sea was refloated and towed to Aker Offshore Partner AS's Stord facility in Norway to await final disposition (Fig. 1). Phillips Petroleum Co. UK Ltd. operated the 110,000-tonne steel, gravity-based Maureen Alpha platform in UK Block 16/29a.
Phillips hopes that the Maureen Alpha platform, shown under tow off Norway, may be used again as an oil production facility (Fig. 1).
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Last June, the largest and heaviest nonconcrete structure in the North Sea was refloated and towed to Aker Offshore Partner AS's Stord facility in Norway to await final disposition (Fig. 1). Phillips Petroleum Co. UK Ltd. operated the 110,000-tonne steel, gravity-based Maureen Alpha platform in UK Block 16/29a.

Phillips had designed the platform to be refloated, and during its operation life the facility handled more than 200 million bbl produced from the Maureen field between 1983 and 1999.

"The refloating of Maureen is a notable achievement," said Henry McGee, president of Phillips's European Division. "Twenty years ago, Phillips' engineers looked into the future, designing and building a unique structure which, now that the Maureen reservoir is depleted, has been removed from the seabed and refloated."

The installation is the first to be removed in the North Sea under OSPAR 98/3, the accord passed in 1998 that requires the removal of all redundant offshore oil and gas platforms weighing more than 10,000 tonnes in the northwestern European continental shelf.

Phillips says the platform will remain at Aker's deepwater Stord yard until a decision regarding its reuse or dismantling can be made.

The 60-hr refloat involved injecting water under the base while deballasting seawater in the structure's three tanks. To maintain internal pressure, the process simultaneously injected nitrogen into the tanks as water was pumped out. The displaced seawater was pumped into a dedicated tanker during the refloat and will be transported to a facility ashore at Sture, Norway, for cleaning and disposal.

Phillips began planning for the refloat in 1993. Over the last 2 years, it has conducted a public consultation program on its decommissioning plans, involving about 300 stakeholder organizations and individuals with an interest in Maureen's removal.

Phillips's remaining program to fully decommission Maureen field involves removal and refloating of the articulated loading column; cleaning and burial of the 2.3-km pipeline from the platform to the loading column; and removal of the drilling template beneath the platform for recycling and disposal.

McGee stressed that the Maureen owners (Phillips, Fina Exploration Ltd., Agip UK Ltd., BG Group PLC, and Pentex Oil UK Ltd.) want Maureen Alpha used again as an oil facility but that partial-use options are also being mulled as a preferred alternative to dismantling and recycling.

The one subsea well Moira satellite facility, 10 km from the platform, along with its associated pipelines and umbilicals, was removed over the last year and brought ashore for recycling and disposal.