Patent Application
20120292014
The field of the invention is packers or bridge plugs used in subterranean locations and more particularly where the set support to the surrounding tubular is made with an extending anchoring member that bonds to the surrounding tubular.
Packers and bridge plugs typically have one or more seal rings that are flanked by slips. Slips are tapered elements that ride up cones that are brought closer together in opposite directions toward the sealing element. As a result the sealing element is compressed and the slips are forced out radially as well to get a penetrating bite into the surrounding tubular. This penetration is accomplished with serrations or wickers on the face of the slips that contacts the tubular. In some applications hardened carbide inserts are teamed up with wickers to enhance the grip of the packer or the bridge plug.
While the wickers and inserts increase the support for the packer or the bridge plug against differential pressures, they also can cause localized stresses in the surrounding tubular that over time can cause cracks and even leakage. Any such occurrence would then require a production outage and a very expensive workover to patch the casing, for example. If for any reason the packer or bridge plug has to be drilled out, the penetrating wickers make the milling more difficult not only from the perspective that they are penetrating the casing wall but also from the perspective that they made be fabricated or cast from materials that increase the milling time to get the packer or the bridge plug to release.
The trend has been to make slips bite the casing and in some instances to produce the slip from a cast material that is fairly brittle as an aid in breaking up the slips to get the packer or bridge plug to release when milling. The present invention seeks to go in a new direction by using a bonded connection of the slip to the surrounding tubular. In the preferred embodiment the slip preferably has an acrylic adhesive applied to the contact face with the tubular. A removable cover that comes off at the desired depth in a variety of ways can be incorporated to protect the bonded face before application against the surrounding tubular. Surface roughening of the bonded slip face and of the surrounding tubular can also increase the strength of the bonded grip. The slip materials and for that matter the components of the packer or bridge plug can be non-metallic or composite materials, for example that will also shorten the milling out time. Conventional setting mechanisms can be deployed to extend the slips and trigger the bond that are for example accomplished with string manipulation, wellbore hydrostatic or with pressure in the tubing applied from the surface. Those skilled in the art will more readily appreciate various aspects of the invention from a review of the description of the preferred embodiment and the associated drawings while keeping in mind that the full scope of the invention is to be determined by the appended claims.
A packer or bridge plug has slips that bind to the surrounding tubular with an adhesive bond. The tubular wall is not penetrated but a roughening of the target location in the tubular can help the bond material to adhere to support the packer or bridge plug. A removable cover can overlay the surface to be bonded to the tubular and the cover can come off in a variety of techniques before the members to be bonded are radially extended. An acrylic adhesive can be the bonding agent. The packer or bridge plug can be made of mostly or entirely non-metallic materials to facilitate mill out.
Several design options are contemplated. The adhesive 36 can be applied to a roughened surface on the outer face of the slips 20 or 22. Instead of slips that straddle the seal 14 the slip pair can be a single bidirectional slip that appears above or below the seal 14. If it is known ahead of time when the tubular 34 is run into a wellbore where the packer or bridge plug is to be set, then the interior surface of the tubular 34 can be roughened to enhance the grip area and improve resistance to applied differential pressures. The material for the slips 20 or 22 can be of a non-metallic or composite material to facilitate milling out.
The use of a bonded relationship between the slips and the surrounding tubular avoids penetration into the wall of the surrounding tubular 34 that occurs with slips that have external wickers and hardened inserts that are expressly designed to penetrate the wall of the surrounding tubular. The objective with slips 20 and 22 is to firmly grab by radial extension and adhere with the adhesive to retain the packer or bridge plug in position against differentials in either direction.
The setting mechanism can be mechanical through string manipulation with drag blocks or tubing pressure or annulus hydrostatic pressure or other known setting devices for packers and bridge plugs. In the run in position, the slips are retracted radially further in toward the mandrel 12 than the sealing element 14 or associated backup rings that are not shown but well known in the art. The use of the bonding relationship will facilitate milling out especially if the components are non-metallic. The bond relationship will offer less resistance to milling making the removal process faster. The avoidance of wall penetration will create less wall stress in the casing or tubing to which the slips are adhered so as to avoid risk of cracks that would bring on the need for a costly workover.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below:
