초록 ▼

An underreamer opens a borehole below a restriction that is larger than the restriction itself. The underreamer includes cutters which engage the formation by traversing outward and upward. The force pushing the cutters to the extended position is supplied by a piston built into each cutter support.

An underreamer opens a borehole below a restriction that is larger than the restriction itself. The underreamer includes cutters which engage the formation by traversing outward and upward. The force pushing the cutters to the extended position is supplied by a piston built into each cutter support. Pressure acting on these pistons comes from the pressure differential between the annulus and drill string during circulation of drilling fluid. The cutters are supported on both sides of the cutting structure by arms that are supported by and in sliding contact with the body. A spring opposes the upward and outward motion of the cutter mechanism and returns the cutters to their collapsed position in the absence of differential pressure. The body of the tool incorporates by-pass ports for transmitting fluid through the tool to the remainder of the bottom hole assembly.

대표청구항 ▼

1. An underreamer comprising:an underreamer body; first and second cutter assemblies slidably disposed within the body for selective movement between a collapsed position and a radially extended position; each said cutter assembly presenting a fluid pressure receiving area and movable from the colla

1. An underreamer comprising:an underreamer body; first and second cutter assemblies slidably disposed within the body for selective movement between a collapsed position and a radially extended position; each said cutter assembly presenting a fluid pressure receiving area and movable from the collapsed position to the radially extended position upon application of fluid pressure to said fluid pressure receiving area.