Fastener for use in an oil tool and oil tool provided with such a fastener

摘要

A casing slip joint has been invented that has a first tubular casing member disposed around and releasably connected to a second casing member, the second casing member within and surrounded by the first casing member. Self-destructive shear screws according to the present invention releasably hold the first casing member to the second casing member. In one aspect, a shear screw according to this invention has an outer shear screw with a central recess and an inner member therein. In one aspect the outer shear screw is made of one metal and the inner screw is made of another so that contact by a well fluid sets up a galvanic cell that produces stress corrosion cracking in the outer shear screw that weakens it and/or destroys it. The propagation of such cracks is facilitated by placing one or more notches or recesses in the body of the components.