Axially Articulated and Rotationally Locked Backup Ring Assembly for a Sealing Element
A backup or extrusion barrier ring assembly has multiple rows of rings in segments that have circumferentially offset slots. The rings are rotationally locked to each other to maintain the circumferential offset of the slots that allow the rings to be more flexible in the setting process. The rings as a unit can be mounted to relatively rotate on a supporting mandrel. The rings are mounted to allow them to move axially during setting either in tandem or axially relatively to each other. The axial run in heights of rings decline from innermost to outermost so that when set the heights approach each other to minimize or eliminate sharp ends against the seal. Alternatively, the height difference can be such as to allow ends to bend over an adjacent end further out radially so that free ends bend toward the surrounding tubular and avoid the seal.
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The field of the invention is sealing systems for subterranean tools against tubular or open hole or cased hole and more particularly anti-extrusion barriers for low, medium and extended reach for a seal element.
BACKGROUND OF THE INVENTIONIn the unconventional drilling and completion industry, oil and gas deposits are often produced from tight reservoir formations through the use of fracturing and frack packing methods. To frack a well involves the high pressure and high velocity introduction of water and particulate media, typically a sand or proppant, into the near wellbore to create flow paths or conduits for the trapped deposits to flow to surface, the sand or proppant holding the earthen conduits open. Often, wells have multiples of these production zones. Within each production zone it is often desirable to have multiple frack zones. For these operations, it is necessary to provide a seal known as a frack packer, between the outer surface of a tubular string and the surrounding casing or borehole wall, below the zone being fractured, to prevent the pumped fluid and proppant from travelling further down the borehole into other production zones. Therefore, there is a need for multiple packers to provide isolation both above and below the multiple frack zones.
A packer typically consists of a cylindrical elastomeric element that is compressed axially, or set, from one end or both by gages within a backup system that cause the elastomer to expand radially and form a seal in the annular space. Gages are compressed axially with various setting mechanisms, including mechanical tools from surface, hydraulic pistons, atmospheric chambers, etc. Setting typically requires a fixed end for the gages to push against. These fixed ends are often permanent features of a mandrel but can include a dynamic backup system. When compressed, the elastomeric seal has a tendency to extrude past the gages. Therefore, anti-extrusion backups have become common in the art. However, typical elastomeric seals maintain the tendency to extrude through even the smallest gaps in an anti-extrusion backup system.
In cased-hole applications, anchoring of compression set packers is a common feature in the completion architecture. Anchoring is provided by wedge-shaped slips with teeth that ride up ramps or cones and bite into the casing before a packer is set. These systems are not part of the backup system nor are they designed to provide anti-extrusion. Often they are used in the setting of the packer to center the assembly which lowers the amount of axial force needed to fully set the elastomer seal. Once set, anchoring systems are also useful for the life of the packer to provide a uniform extrusion gap, maintain location and help support the weight of a bottom-hole assembly in the case of coiled tubing frack jobs. Anchors also prevent tube movement in jointed strings resulting from the cooling of the string by the frack fluid. Movement of the packers can cause them to leak and lose seal.
In open-hole frack pack applications it is rarer for the packer to have anchoring mechanisms, as the anchor teeth create point load locations that can overstress the formation, causing localized flow paths around the packer through the near well-bore. However, without anchors, movement from the base pipe tubing can further energize the elastomeric seal. Energizing the seal from tube movement tends to overstress the near wellbore as well, leading to additional overstressing of the wellbore, allowing communication around the packer, loss of production, and potential loss of well control to surface. However, the art of anchoring has been reintroduced in new reservoirs in deep-water open-hole fracking operations. The current state of the art in open-hole frack pack operations requires a choice between losing sealing due to anchor contact induced fractures, packer movement, or over-energizing of the elastomeric element.
Extrusion barriers involving tapers to urge their movement to block an extrusion path for a sealing element have been in use for a long time as evidenced by U.S. Pat. No. 4,204,690. Some designs have employed tapered surfaces to urge the anti-extrusion ring into position by wedging them outwardly as in U.S. Pat. No. 6,598,672 or in some cases inwardly as in U.S. Pat. No. 8,701,787. Other designs simply wrap thin metal rings at the extremities of the sealing element that are designed to contact the surrounding tubular to create the anti-extrusion barrier. Some examples of these designs are U.S. Pat. No. 8,479,809; U.S. Pat. No. 7,708,080; US 2012/0018143 and US 2013/0147120. Of more general interest in the area of extrusion barriers are U.S. Pat. No. 9,140,094 and WO 2013/128222.
In some applications the gap across which the seal is expected to function is quite large placing such applications beyond the limits of the design in U.S. Pat. No. 6,598,672.
The present invention addresses operational issues in the past with a multi-layer ring assembly of nested rings with circumferentially offset slots where the ring heights decline from the innermost to the outermost rings in the assembly. The rings are rotationally locked to each other to maintain the slot circumferential offset. The nested ring assembly is mounted for axial relative articulation during the set so that the number of sharp edges exposed to the sealing element is reduced if not eliminated. The free ends of rings inside the outermost ring can be bent by the sealing element during the setting in a way to protect the sealing element from sharp ends as the ends of the rings are protected by an adjacent ring and the innermost ring is bent toward the surrounding tubular to shield sharp ends of the rings further out from contact with an end of the sealing element. These and other aspects of the present invention will be more readily understood from a review of the description of the preferred embodiments while recognizing that the full scope of the invention is to be determined by the appended claims.
SUMMARY OF THE INVENTIONA backup or extrusion barrier ring assembly has multiple rows of rings in segments that have circumferentially offset slots. The rings are rotationally locked to each other to maintain the circumferential offset of the slots that allow the rings to be more flexible in the setting process. The rings as a unit can be mounted to relatively rotate on a supporting mandrel. The rings are mounted to allow them to move axially during setting either in tandem or axially relatively to each other. The axial run in heights of rings decline from innermost to outermost so that when set the heights approach each other to minimize or eliminate sharp ends against the seal. Alternatively, the height difference can be such as to allow ends to bend over an adjacent end further out radially so that free ends bend toward the surrounding tubular and avoid the seal.
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Those skilled in the art will appreciate that a backup ring assembly features multiple rings with circumferentially spaced slots to avoid extrusion paths also has a rotational locking feature to maintain relative orientations that preclude extrusion gaps from forming in the set position. The rings further have a capability of rotating in tandem with respect to the mandrel and of travelling axially relative to each other while still retained to the mandrel. The rings have different axial heights to allow the reduction or elimination of sharp ends facing the sealing element in the set position. The set position brings the ends of the rings closer to an alignment of their ends so that a blunt face is opposite the sealing element. The run in height differences also allow ends of inner rings to bend over ends of adjacent rings so that the sealing element sees a bent end of the innermost ring which is blunt. The ends of some of the rings other than the outermost can be bent for the run in position to encourage better end contact with the surrounding tubular as well as avoiding sharp ring ends from cutting into the sealing element. The ability of the rings to slide axially relatively to each other can be controlled with studs that force the rings toward a supporting mandrel. A bushing or bearing allows the assembly of all the rings to rotate in tandem relative to the mandrel to assure a better peripheral connection to the surrounding tubular to reduce or eliminate extrusion paths along the surrounding tubular wall.
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:
Claims
1. An extrusion barrier assembly for a mandrel mounted sealing element in a borehole barrier, comprising:
- a plurality of nested discrete rings mounted to the mandrel for relative axial movement, with respect to the mandrel, of first ends of said rings nearest the mandrel when second ends of said rings are radially actuated from a run in position adjacent said mandrel to a set position in contact with a surrounding borehole wall.
2. The assembly of claim 1, wherein:
- said rings comprise a plurality of axially oriented slots extending from a first axial end thereof, with said slots in adjacent rings circumferentially offset so as to avoid extrusion gaps in said set position.
3. The assembly of claim 2, wherein:
- said rings are rotationally locked with respect to each other to maintain said circumferential offset of said slots.
4. The assembly of claim 3, wherein:
- said rings are rotatably mounted to said mandrel.
5. The assembly of claim 3, wherein:
- said rings each comprise at least one axial keyway such that keyways in said rings are aligned to accept a retainer that permits relative axial movement of said rings and precludes relative rotation between said rings.
6. The assembly of claim 5, wherein:
- said keyways begin at a second axial end opposite said first axial end.
7. The assembly of claim 3, wherein:
- said rings are retained to said mandrel with a retainer ring further comprising a lateral opening for advancing a force regulating retainer radially against said rings to regulate the force required to relatively move said rings in an axial direction.
8. The assembly of claim 7, wherein:
- said rings each comprise at least one axial keyway such that keyways in said rings are aligned to accept a keyway retainer that permits relative axial movement of said rings and precludes relative rotation between said rings.
9. The assembly of claim 3, wherein:
- said slots widen as between said run in and set positions while remaining circumferentially offset as between adjacent said rings.
10. The assembly of claim 3, wherein:
- said rings vary in axial length in said run in position at said first axial end thereof.
11. The assembly of claim 10, wherein:
- said rings comprise a longest in axial length innermost said ring and a shortest in axial. length outermost said ring to define an initial run in height difference, said height difference being reduced in said set position.
12. The assembly of claim 10, wherein:
- said rings comprise a longest in axial length innermost said ring and a shortest in axial length outermost said ring to define an initial run in height difference, said height difference being eliminated in said set position.
13. The assembly of claim 10, wherein:
- at least one of said rings at said first axial end thereof bends over a said first axial end of an adjacent ring when moved to said set position.
14. The assembly of claim 10, wherein:
- at least one of said rings at said first axial end thereof is bent over a said first axial end of an adjacent ring in said run in position.
15. An extrusion barrier assembly for a mandrel mounted sealing element in a borehole barrier, comprising:
- a plurality of nested discrete rings mounted to the mandrel having first ends of said rings nearest the mandrel and second ends, said second ends of said rings are radially actuated from a run in position adjacent said mandrel to a set position in contact with a surrounding borehole wall;
- said rings comprise a plurality of axially oriented slots extending from a first axial end thereof, with said slots in adjacent rings circumferentially offset so as to avoid extrusion gaps in said set position;
- said slots widen as between said run in and set positions while remaining circumferentially offset as between adjacent said rings;
- said rings vary in axial length in said run in position at said first axial end thereof.
16. The assembly of claim 15, wherein:
- said rings comprise a longest in axial length innermost said ring and a shortest in axial length outermost said ring to define an initial run in height difference, said height difference being reduced in said set position.
17. The assembly of claim 15, wherein:
- said rings comprise a longest in axial length innermost said ring and a shortest in axial length outermost said ring to define an initial run in height difference, said height difference being eliminated in said set position.
18. The assembly of claim 15, wherein:
- at least one of said rings at said first axial end thereof bends over a said first axial end of an adjacent ring when moved to said set position.
19. The assembly of claim 15, wherein:
- at least one of said rings at said first axial end thereof is bent over a said first axial end of an adjacent ring in said run in position.
20. An extrusion barrier assembly for a mandrel mounted sealing element in a borehole barrier, comprising:
- a plurality of nested discrete rings mounted to the mandrel having first ends of said rings nearest the mandrel and second ends, said second ends of said rings are radially actuated from a run in position adjacent said mandrel to a set position in contact with a surrounding borehole wall;
- said rings comprise a plurality of axially oriented slots extending from a first axial end thereof, with said slots in adjacent rings circumferentially offset so as to avoid extrusion gaps in said set position;
- said slots widen as between said run in and set positions while remaining circumferentially offset as between adjacent said rings;
- said rings are rotationally locked with respect to each other to maintain said circumferential offset of said slots.
21. The assembly of claim 20, wherein:
- said rings are rotatably mounted to said mandrel.
22. The assembly of claim 20, wherein:
- said rings each comprise at least one axial keyway such that keyways in said rings are aligned to accept a retainer that permits relative axial movement of said rings and precludes relative rotation between said rings.
23. The assembly of claim 22, wherein:
- said keyways begin at a second axial end opposite said first axial end.
24. The assembly of claim 20, wherein:
- said rings are retained to said mandrel with a retainer ring further comprising a lateral opening for advancing a force regulating retainer radially against said rings to regulate the force required to relatively move said rings in an axial direction.
25. The assembly of claim 24, wherein:
- said rings each comprise at least one axial keyway such that keyways in said rings are aligned to accept a keyway retainer that permits relative axial movement of said rings and precludes relative rotation between said rings.
26. The assembly of claim 1, wherein:
- said rings are made from abutting or selectively attached segments.
27. The assembly of claim 15, wherein:
- said rings are made from abutting or selectively attached segments.
28. The assembly of claim 20, wherein:
- said rings are made from abutting or selectively attached segments.
Type: Application
Filed: Nov 1, 2017
Publication Date: May 2, 2019
Applicant: Baker Hughes, a GE company, LLC (Houston, TX)
Inventors: Daniel Guerra (Sugar Land, TX), Guijun Deng (The Woodlands, TX), Alexander M. Kendall (Houston, TX), John K. Wakefield (Cypress, TX)
Application Number: 15/800,966