Decommissioning and abandonment

Decommissioning and abandonment

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If additional weight needs removal, then an ROV or divers could cut the straps and release some of the chains. When it has been towed to the new location in the on-bottom configuration, the weight would be restored by reflooding and the addition of weight blocks or concrete mattresses. At least one reusable bundle has recently been installed in the North Sea. The Goosander field, some 12 km (7½ miles) northwest of Kittiwake (in block 21/12 of UK sector of the North Sea) is being developed by Venture using a reusable pipeline bundle, fabricated in two main sections, 4.9 km (3 miles) and 7.4 km (4½ miles) long, both of which were engineered and installed by Subsea 7. The bundles each comprise a 219.1 mm (8⅝ in) production flowline, a 168.3 mm (6⅝ in) water injection flowline, a 101.6 mm (4 in) gas lift line, and a chemical injection/control line. The system has also been designed to allow other fields to flow through the infrastructures. Currently, the bundle is still producing at the original field.

RIGIDFLOWLINES

RIGID FLOWLINES

ƒ Bottom tow to near-by location ƒ Re-reel ƒ Issue of total plastic strain ƒ Weld fatigue

ƒ Serious issues with weld quality after internal corrosion ƒ JIP currently underway at The Welding Institute ƒ Unlikely to be financially viable

Bottom tow can also be used to relocate rigid pipelines at a new route nearby. Although flowlines can be recovered onto a reel barge, there are some concerns with the condition of the welds when subject to additional cumulative yielding again during recovery and reinstallation. This is particularly the case when considerations of corrosion are allowed for. Neither is likely to be economic. Which operator wants to start production with all the damage from a previous operation?

RE-USESUMMARY