Recovery of jammed drill strings, in which tool including cutters separates drill pipe permitting expansive sections to grip interior, for extraction by existing surface equipment

摘要

The recovery cutting head is used as combined tool and cutting bit, at the end of an existing rotary drilling string, using the existing drilling carriage to introduce and drive the tool. An Independent claim is also included for the equipment used in the recovery of jammed drill strings, comprising a single-acting hydraulic cylinder with a piston connected to the cutting tool, with the tool floating on a return spring in the grease-filled damper chamber. The piston rod acts on cams to convert longitudinal motion into radial motion of the cutting edge and spacer. The spacer is extended before separation. The rate constant of the damping chamber is adjustable. Enlargement is possible by replacing the cutter and spacer.