Well Abandonment Procedure

In a typical well abandon procedure a semi-submersible drill rig will be mobilised to the field and set up over the cluster wells on an eight-point mooring. The riser system is deployed with a lower riser package that latches onto the subsea tree.  A general procedure is presented below which will be adjusted to suit the individual well details.

The following typical outlined operations would be performed for the well abandonment:

• Pull tree cap.
• Run subsea wireline lubricator onto tree.
• Re-establish control of tree valves through the riser control panel.
• Bullhead tubing contents with kill weight fluids.
• Perforate tubing above packer.
• Bullhead annulus contents to kill weight fluid.
• Flush tie-in spools to seawater.
• Bullhead cement to approximately 30.5m (100ft) minimum above the producing zone.
• Set mechanical plug in tubing just below perforations and pressure test.
• Set a 30.5m (100ft) minimum cement plug in the tubing and annulus above the mechanical plug.
• Tag and pressure test cement plug.
• Perforate tubing and casings below 3m (10ft) removal level.
• Set mechanical plug in tubing just below perforations
• Set a cement plug in the tubing and annuli to seal casing annuli.
• Disconnect tie-in spools and umbilical from tree.
• Pull tree and recover to the surface.
• Cut tubing below tubing hanger and at least 5m below seabed level.
• Pull tubing hanger and tubing stump.
• Mill casings to severe at least 3m (10ft) below seabed level.
• Recover wellhead and casing stumps.
 

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