Hole Opening in Hard Formations

18 November 2011 We have a planned hole opening run to open a 12¼" pilot section to 17½ in a deepwater well offshore Brazil. Of the c.1000m section there is an interval of about 150m of mainly limestone with cemented sandstone and claystone which drilled slower than we anticipated [2-3 m/h with a 6 blade 16mm cutter PDC with 45k WOB RS assembly]. This interval is PDC drillable looking at the DT from a LWD sonic log (80micro-s/ft).

Base plan is to run a fixed cutter staged hole opener from NOV. The tool has a profile to 14¾" followed by another to 17½. It too has 16mm PDC cutters. I have some concerns that it may ring out or at least produce a lot of torque in the harder section.

Anyone got any experience with alternatives in harder formation ? - Rhino/XS reamer from Halliburton etc.. We want to go straight to 17½ if possible.

Thanks,

David.

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