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DECOMMISSIONING INSIGHT REPORT
2016
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Rig Type
There are a number of methods that can be used for well P&A and the rig type will primarily depend on the well type
and water depth. In some instances, the availability of well P&A technologies could remove the requirement for a
rig altogether. For example, a low-cost method of well P&A without the requirement of a rig was recently trialled
onshore by Centrica in Canada in a collaboration with Interwell P&A, BP, Statoil, and the Norwegian Research
Council. The new technology uses a thermite plug to seal off the well by melting both the well components and the
rock formation around them to recreate the cap rock. The trial results demonstrated that this technology could
potentially reduce well P&A costs in the North Sea by more than 50 per cent.
Platform wells are typically plugged and abandoned in phases. The first phase can be rig-less and uses lower cost
methods such as wireline, coil tubing, or a hydraulic workover unit. This is followed by the second and third phases
that are more likely to require a rig.
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For platform wells on the central and northern North Sea and west of Shetland, and the Norwegian Continental
Shelf, 86 and 68 per cent, respectively, will be plugged and abandoned using an integral rig.
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Modular rigs are also popular for platform well P&A in Norway, although most of the wells using this rig type fall
outside the survey timeframe.
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For operators planning to use an integral rig for platform well P&A, the opportunity exists for alternative
approaches that preclude the use of the platform’s existing drilling derrick, which can prove challenging and
expensive to upgrade.
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In the southern North Sea and Irish Sea, the majority (64 per cent) of platform wells will be plugged and
abandoned using a standalone jack-up rig.
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Operators are also considering rig-less, lower cost solutions to well P&A. For example, in the southern North Sea
and Irish Sea, 30 per cent of platform wells are forecast to use rig-less methods such as coil tubing and wireline.
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For subsea wells, a standalone jack-up rig will be used for 98 per cent of wells on the Norwegian Continental
Shelf and 70 per cent on the southern North Sea and Irish Sea.
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In the central and northern North Sea and west of Shetland, 63 per cent will use a semi-submersible rig for
subsea well P&A due to the greater water depths.
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For a greater proportion of subsea wells, the rig type has not yet been determined as operators consider
alternative solutions (25 per cent in the southern North Sea and Irish Sea and 19 per cent in the central and
northern North Sea and �est of Shetland).