This invention relates generally to downhole tools for use in oil and gas wellbores, and methods of anchoring such apparatuses within the casing of the wellbore. This invention particularly relates to improving the engagement of slip elements within a casing or tubing. These slip elements are commonly used in setting or anchoring of a downhole drillable packer, bridge plug and frac plug tools.
In drilling or reworking oil wells, many varieties of downhole tools are used. For example, but not by way of limitation, it is often desirable to seal tubing or other pipe in the casing of the well by pumping cement or other slurry down the tubing, and forcing the slurry around the annulus of the tubing or out into a formation. It then becomes necessary to seal the tubing with respect to the well casing and to prevent the fluid pressure of the slurry from lifting the tubing out of the well, or for otherwise isolating specific zones in a well. Downhole tools referred to as packers, bridge plugs and frac plugs are designed for these general purposes, and are well known in the art of producing oil and gas.
Both packers and bridge plugs are used to isolate the portion of the well below the packer or bridge plug from the portion of the well thereabove. Accordingly, packers and bridge plugs may experience a high differential pressure, and must be capable of withstanding the pressure so that the packer or bridge plug seals the well, and does not move in the well after being set.
Packers and bridge plugs used with a downhole tool both make use of metallic or non-metallic slip assemblies, or slips, that are initially retained in close proximity to a mandrel, These packers and bridge plugs are forced outwardly away from the mandrel upon the downhole tool being set to engage a casing previously installed within an open wellbore. Upon positioning the downhole tool at the desired depth, or position, a setting tool or other means of exerting force, or loading, upon the downhole tool forces the slips to fracture and expand radially outward against the inside of the casing. This action anchors the packer, or bridge plug, so that the downhole tool will not move relative to the casing.
To prevent slipping of the downhole tool, slip rings with wickers are used to set the downhole tool and engage the well casing. The wickers cut into and deform the inner casing wall. Unfortunately, the outer diameter of the slip rings and wickers is notably smaller than the inner diameter of the casing. Thus, the wickers only partially and unevenly engage the casing wall, thereby allowing the downhole tool to slide within the well.
In one embodiment, an apparatus for use in a well is provided. The apparatus is for anchoring a downhole tool against a casing disposed in the well. The apparatus comprises a mandrel and a slip assembly. The slip assembly is positioned on the mandrel. The slip assembly has at least one slip ring. There are a plurality of slip banks formed on the slip ring. The slip banks have a groove longitudinally positioned between each circumferential pair of slip banks. The slip ring has an outer diameter about equal to the inner diameter of the casing.
In another embodiment, a unitary downhole anchor for use in a well having a casing positioned therein is provided. The casing has an inner diameter. The unitary downhole anchor comprises a mandrel and a slip assembly. The slip assembly is positioned on the mandrel. The slip assembly has at least one outwardly expandable slip ring and at least one slip wedge. The slip ring is a unitary slip ring. The slip wedge and slip ring are movable relative to one another when force is applied to the slip assembly, whereby the slip ring will expand radially outward in response to such movement. There are a plurality of slip banks circumferentially defined on the slip ring. The slip ring has at least one circumferential pair of slip banks. The slip banks have a groove longitudinally positioned between each circumferential pair of slip banks. The slip ring has an outer diameter about equal to the nominal inner diameter.
In yet another embodiment, an evenly setting anchor apparatus for anchoring a downhole tool in a well, the well having a casing secured therein, is provided. The apparatus comprises a mandrel and at least one slip assembly that is positioned on the mandrel. The slip assembly has at least one slip ring and at least one slip wedge. Each slip ring has a plurality of radially expandable slip banks. There are a plurality of wickers defined on each of the slip banks. Each of the wickers has a cutting edge extending therefrom, wherein the wickers are positioned to evenly set against an inner wall of the casing in response to an input force.
In still another embodiment, a downhole tool anchoring apparatus for use in high-pressure wells is provided. The high-pressure well has a casing and the casing has an inner diameter. The apparatus comprises a mandrel and a slip assembly. The slip assembly is positioned on the mandrel. The slip assembly has at least one slip ring. The slip bank is defined on the slip ring. The slip bank has at least one wicker integrally formed therewith. The wicker is designed to engage and anchor the downhole tool within the casing in the high-pressure well.
Referring to the drawings,
By way of a non-limiting example, downhole tool 18 illustrated in
As illustrated in
Slip ring 38, shown in
Preferably, each slip bank 48 defines at least one wicker 54 thereon. As illustrated, a plurality of wickers are defined on each slip bank 48. The number of wickers 54 on each slip bank 48 is determined by the size of casing 14 and the pressure slip ring 38 is designed to resist. The non-limiting example illustrated in
Wicicers 54 are positioned on slip bank 48 such that each cutting edge 56 is able to be evenly set against casing inner wall 16. Thereby, each cutting edge is nearly equal in the force exerted upon casing inner wall 16. Thus, each cutting edge 56 is better able to penetrate and/or deformably cut into casing inner wall 16. This action securely anchors downhole tool 18.
Including wickers 54 and cutting edge 56, slip ring 38 has an outer diameter 58 that is about equal to inner diameter 60 of casing 14. A non-limiting example is illustrated in
Slip rings 38 are comprised of a drillable material and may be, for example, cast iron or a molded phenolic. Slip rings 38 may be made from other drillable materials such as drillable metals, composites and engineering grade plastics. The remainder of slip assembly 36 and other components of the tool may likewise be made from drillable materials.
Slip assemblies 36a and 36b are illustrated in
Referring to the example illustrated in
Regarding
Slip ring 38 has true centerline 86 and offset centerline 88. Offset centerline 88 is the centerline for slip ring 38 after slip banks 48 have been fractured by slip wedge 40. As illustrated in
Regarding
Another alternative embodiment of slip ring 38 is illustrated in
In operation, downhole tool 18 is positioned at the desired depth or location by a setting tool, such as a wireline. The wireline exerts an initial or first force upon slip assembly 36, causing slip wedge 40 and slip ring 38 to move relative to one another, which radially exerts an internal radial force upon slip ring 38. Slip wedge 40 has inclined surface 42 defined thereon. Slip ring 38 radially expands outward as complementary second surface 44 slides against inclined first surface 42 of slip wedge 40. The sliding effect of complementary second surface 44 against inclined first surface 42 causes slip ring 38 to force cutting edge 56 of wickers 54 defined on slip bank 38 against casing inner wall 16. As the radial force is increased, cutting edge 56 of wickers 54 penetrate into casing inner wall 16. This radial force is sufficient to penetrate the casing grade for the particular casing 14 utilized, thereby setting downhole tool 18.
Other embodiments of the current invention will be apparent to those skilled in the art from a consideration of this specification or practice of the invention disclosed herein. Thus, the foregoing specification is considered merely exemplary of the current invention with the true scope thereof being defined by the following claims.