FIELD OF THE INVENTION

This invention relates in general to extrusion limiters for retrievable downhole pressure isolation packers used in cased well bores, such as straddle packers and, more particularly, to a pre-set inhibiting, extrusion limiter for retrievable packers.

BACKGROUND OF THE INVENTION

Retrievable packers for isolating fluid pressure in cased well bores are known in the art. One type of retrievable packer is the “straddle packer”. Straddle packers are used to isolate well stimulation fluid pressure within a confined zone in a cased or open well bore. Straddle packers have a pair of spaced-apart packer elements that are respectively set to isolate the confined zone in the well bore during hydrocarbon well completion or re-completion operations. The straddle packer elements are designed to be repeatedly set and unset so the straddle packer can be moved from one location to another in the well bore. As understood by those skilled in the art, most well bores being drilled today are lateral bores. As further understood by those skilled in the art, lateral bores are often somewhat corkscrew-shaped and therefore tend to resist the insertion of lengthy well tools such as straddle packers. That resistance and/or minor obstructions in the well bore, such as casing collars in cased well bores, or the like, can urge the packer elements to pre-set before the straddle packer has been moved to a target location in the well bore. Packer element pre-set is undesirable for many reasons and may result in damage to elastomeric packer element(s).

It is also well known that the hydraulic pressures required for stimulating a hydrocarbon production zone during well completion or recompletion operations can cause elastomeric packer elements to extrude and lose their fluid seal. Packer element extrusion limiters have therefore been invented to inhibit the extrusion of elastomeric packer elements during hydraulic well stimulation. While extrusion limiters are effective in controlling packer element extrusion, they may precipitate packer element pre-set if they snag an obstruction in a cased or open well bore.

There therefore exists a need for a novel pre-set inhibiting extrusion limiter for retrievable packers.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a novel pre-set inhibiting extrusion limiter for retrievable packers.

The invention therefore provides a pre-set inhibiting extrusion limiter for a packer element of a retrievable packer, comprising a stepped cone frustum that supports a plurality of anti-extrusion ring segments held together by a retainer ring that is retained in a retainer ring groove in the respective anti-extrusion ring segments and retains a respective compression spring for each of the respective anti-extrusion ring segments.

The invention further provides a pre-set inhibiting extrusion limiter for a packer element of a retrievable packer comprising: a stepped cone frustum; and a segmented anti-extrusion ring that comprises a plurality of identical anti-extrusion ring segments held together by an elastomeric ring received in an elastomeric ring groove in a the respective anti-extrusion ring segments and a retainer ring received in a retainer ring groove in the respective anti-extrusion ring segments, a bottom of the respective retainer ring grooves comprising a ring segment spring socket that receives an end of a compression spring having an opposite end retained in a respective retainer ring spring socket in the retainer ring.

The invention yet further provides a pre-set inhibiting extrusion limiter for a packer element of a retrievable packer comprising: a stepped cone frustum; a segmented anti-extrusion ring that comprises a plurality of identical anti-extrusion ring segments held together by an elastomeric ring received in an elastomeric ring groove in the respective anti-extrusion ring segments and a retainer ring received in a retainer ring groove in the respective anti-extrusion ring segments, a bottom of the respective retainer ring grooves comprising a ring segment spring socket that receives en end of a compression spring having an opposite end retained in a respective retainer ring spring socket in the retainer ring; and a push ring having a push ring inclined surface that abuts a ring segment push surface of the respective anti-extrusion ring segments.

