Staged Actuation Shear Sub for Use Downhole

Abstract

A shear assembly used downhole to actuate a work string function includes a dampening subassembly to dampen the momentum of moving parts following shearing to avoid excessive acceleration and resulting jarring forces within the work string. A dual shear assembly is provided, in which the dampening subassembly prevents inertial force resulting from a first shear from exceeding the threshold for actuating the second, higher threshold, shear mechanism thereby allowing more precise control of the forces applied to the work string to prevent premature shearing of the second shear mechanism. In a specific embodiment, the dampening subassembly is a hydraulic dampening subassembly. The dual shear assembly may be used, for example, to first open a wash port above a tool lodged within the wellbore to loosen debris above the lodged tool, and then to shear the tool from the work string if necessary.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present invention claims the benefit of U.S. Provisional Patent Application Ser. No. 61 / 012,457 entitled “Staged Actuation Shear Sub for Use Downhole” filed Dec. 9, 2007.FIELD OF THE INVENTION[0002]The present invention relates generally to tools for use within a wellbore. More particularly, the present invention relates to a shear assembly for integration within a work string.BACKGROUND OF THE INVENTION[0003]During use of downhole equipment within a wellbore, sand and other debris may enter the wellbore and accumulate above the bottom hole assembly. From time to time, the tool may become lodged within the wellbore due to this accumulation of debris. Various means of attempting to loosen lodged equipment are known, which generally include pulling (such as the controlled pulling taught by U.S. Pat. No. 7,249,633), vibrating, or reciprocating the bottom hole assembly within the wellbore until same is freed of debris. Unfortunately, thes...

AI Technical Summary

Benefits of technology

[0011]In accordance with a first aspect of the invention, there is provided a shear assembly for use downhole, the shear assembly comprising: a mandrel for integration within a work string; a shear sleeve slideable with respect to the mandrel to actuate a work string function; setting means for setting the shear sleeve in a fixed position with respect to

Problems solved by technology

From time to time, the tool may become lodged within the wellbore due to this accumulation of debris.

Unfortunately, these loosening methods often fail, requiring the bottom hole assembly to be sheared from the tubing string and fished out of the well.

Such fishing operations are expensive and time consuming, as an independent contractor must transport specialized equipment to the site in order to fish the bottomhole assembly from the wellbore.

Once the tubing string has been sheared from the fishneck, the fishneck may remain inaccessible due to further accumulation of debris during shearing and removal of the tubing string.

To date, a shear-actuated wash mechanism has not been incorporated within a work string above a bottom hole assembly for use in freeing the bottom hole assembly should it become lo

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