AMT Pilot Mill Milled ZXP Ultra Liner Top Packer and PBR in One TripAvoided NPT and expense in a complex North Sea milling operation
An operator in a North Sea field needed to remove a 13 Cr 110 ksi 7-in. x 97/8-in., 62.8-ppf (93.75 kg/m) Baker Hughes ZXP™ ultra liner top packer and a FLEX-LOCK™ III liner hanger system. The job presented an extra challenge because the ZXP ultra liner top packer has holddown slips that restrict any upward movement. There were concerns about the risk of skim-cutting the polished bore receptacle (PBR) or damaging the outer casing due to the thin-walled, decentralized liner system in the deviated wellbore. Efficient milling of the 13 Cr 110 ksi material was also very important.
The Baker Hughes wellbore construction and fishing teams evaluated different options to address these concerns. Baker Hughes recommended milling up the liner top packer and PBR with a specially designed casing mill with METAL MUNCHERTM advanced milling technology (AMT) with cutting inserts affixed to specially designed blades to allow for good guiding and centralization throughout the operation.
The ZXP ultra liner top packer was located at 15,748 ft (4799.9 m) in an 18.9° section of the deviated S-shaped well profile. Milling started out with the specially designed 8½-in. pilot milling assembly with initial favorable milling parameters and progress. After the slips of the liner top packer were milled away, progress slowed as packer components became free.
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