Downhole Tool

Abstract

A downhole tool (10′) comprises a body (12′) having a longitudinal axis and a body through-bore (14′), a slot (34′) communicating the outside of the body with the body through-bore. A sleeve actuator (30′) mandrel also has a bore and is selectively axially slidable in the body through-bore. A hollow bar (36′) is slidable with a radial component in the slot. At least two levers (210), each pivoted to the mandrel (about a first axis perpendicular the longitudinal axis) extend into the hollow bar and are pivoted thereto (about a second axis parallel the first axis). The levers lie in an actuation plane perpendicular the first and second axes and containing the slot. The levers are disposed at an inclined angle with respect to the longitudinal axis so that longitudinal motion of the mandrel translates into radial movement of the bar.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of, and priority to, application number 0704484.5, which was filed in the United Kingdom on Mar. 8, 2007, which application is incorporated herein by reference as if reproduced in full below.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]Not applicable.FIELD OF THE INVENTION [0003]The present invention relates to a downhole tool, in particular an under-reamer.BACKGROUND[0004]Our pending international application publication number WO2006 / 072761 (the entire disclosure of which is incorporated herein by reference) discloses a downhole tool comprising:[0005]a body having a longitudinal axis and a body through-bore, a slot communicating the outside of the body with the body through-bore;[0006]a sleeve actuator mandrel having a sleeve actuator mandrel through-bore and being selectively axially slidable in the body through-bore;[0007]a flange on the sleeve actuator mandrel extending into...

AI Technical Summary

Benefits of technology

[0027]Separating the mandrel from the sleeve actuator permits them to move independently when for some stroke movements of the mandrel which is needed for switching between actuation mode and deactuation mode of the tool. Generally, a strong return spring is utilized and, by connecting the mandrel with the sleeve actuator during some movements thereof, the return spring for the mandrel can also serve as the return spring for the bars. Since it is normal to provide signalling in the form of pressure pulses, at least when the tool is actuated, then, by connecting the mandrel to the tool actuator, signalling by the mandrel equates to signalling by the tool, at least when they are interconnected.

[0034]Said body is thickened in the region of said slots and bars to support said bars. The body may have fins ahead of said slots having dimensions to match said pilot hole and bear against its surface and stabilise the tool, in use, said fins being provided with a hardened wear surface to minimise wear.

[0035]Alternatively, the tool may be an adjustable stabiliser, said bars being provided with hardened wear surfaces to minimise wear of the bars, in use.

Problems solved by technology

On the other hand, when components get worn or contorted by their interaction with the bore hole, they may be difficult or impossible to withdraw.

This might be very problematic with an under-reamer where, to get the tool out through a narrow casing above the reamer, the reamer must be withdrawn (deactuated).

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