Two conventional attempts to run a 7-in. liner to total depth (TD) in a Norwegian North Sea well had been unsuccessful, with the liner hanging up hundreds of meters from TD. The problem was caused by borehole instability and severe washout in the weak shales, coals, and notorious paleosols of the area. A sidetrack was drilled successfully, and the liner was run with Deep Casing Tools’ Turbocaser Express as a contingency against wellbore obstructions. The system is a high-speed drillable reaming system that enables drilling teams to land casings and intermediate liners at target depth on the first attempt. If hole conditions prove too severe, the full-bore rapid-drill-through capability of the tool would allow the remaining reservoir to be accessed. The 7-in. liner was run and, as predicted, stopped with 10 t total weight at 4117 m (1260 m from TD), where the liner could not be rotated or run deeper. Circulation was established, and the reaming system was used to clear the obstruction. The next obstruction was at 4378 m, where the tool was used again to ream. This process was repeated most of the way to TD. Total reaming time was 21 hours, at an average rate of 60 m/h.
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