Multi-layer Packer Backup Ring with Closed Extrusion Gaps
An extrusion ring has a base from which multiple segmented rows of rings integrally extend. Gaps in one row are offset from the adjacent row to cover any gaps. The rows gain strength from a common base that also presents relative rotation among the rows.
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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. There is a need for an extended reach design that can withstand the pressure differentials. The present invention addresses this need with slots that extend toward each other from opposing faces and are circumferentially offset. The slots are connected at voids that extend from the original inside to the original outside diameter. Expansion of the ring allows alternating voids to shear at the outside and the inside diameter so that as gaps form in the ring a segment of the ring presents itself in each of the opened gaps as both the inside and the outside diameters increase. In an alternative solution to extrusion through a backup ring a backup ring with a common base has multiple rows of extending segments with gaps in one row offset circumferentially with gaps in an adjacent row. The common base lends structural integrity to the backup ring design and reduces the risk that relative rotation can occur between adjacent rows that would tend to align the offset gaps from one row to the next. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while understanding that the full scope of the invention is to be determined from the appended claims.
SUMMARY OF THE INVENTIONAn extrusion ring has a base from which multiple segmented rows of rings integrally extend. Gaps in one row are offset from the adjacent row to cover any gaps. The rows gain strength from a common base that also presents relative rotation among the rows.
Bores 20″ are seen as alternating with bores 22″ at the outside diameter 18 as seen in
Note that as shown in
Those skilled in the art will appreciate that alternative backup ring designs are described that have the objective of dimensional growth while limiting or eliminating extrusion of a sealing element on preferably opposed ends of a sealing element. In
The same pattern of slots that open into gaps alternating on the inside and outside diameters can be used with dovetail cuts that have slack in them in the run in diameter and where the relative circumferential movement of each pair of dovetail components is limited by the slack coming out of each dovetail connection. The gaps that open are blocked by the extension of the male of the dovetail pair extending into the opening. The dovetail pairs start in an alternating pattern on the inside and outside diameters to present a cohesive ring structure that can expand on the inside and outside diameters. The dovetail slots on the inside diameters are circumferentially spaced from the dovetail slots on the outside diameter and the gaps that form as the diameters increase are substantially blocked by the male dovetail component bottoming on the female surrounding component or when the outside dimension of the backup ring engages a surrounding tubular, whichever happens first. The structure with alternating dog leg slots or dovetail slots lets the ring remain whole while lending the ring flexibility of going out of round so that if the surrounding tubular has dimensional imperfections, the backup ring can adapt to the actual shape of the inside wall of the surrounding tubular. A single ring can be placed between sealing elements and reduce or eliminate extrusion between the sealing element in either of opposed directions.
In a backup ring with multiple stacked rows of segmented rings the gaps in adjacent rings are offset and all the rings are preferably integral to a common ring base. The extrusion gaps are closed off while the integration of the stacked rings with the base provides for a stronger yet still flexible design that can conform to the surrounding tubular wall for closing an extrusion gap. The outer edge of the stacked rings is made long enough so that there is bending into a more parallel orientation with the surrounding tubular when the set position of
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. A mandrel mounted backup ring assembly for extrusion protection for a mandrel mounted sealing element of a borehole barrier, comprising:
- a ring comprising an axis, said ring mounted to the mandrel on at least one end of the sealing element and further comprising axially extending segments integrally extending from said ring at spaced locations from said mandrel, said segments integrally extending from said ring at a spaced radial locations to the mandrel, said base axially movably mounted to the mandrel for tandem axial movement with the sealing element to a set position of the borehole barrier, said segments extending from said ring at multiple diameters with respect to said mandrel with segments at each diameter forming a ring shape with gaps wherein gaps in adjacent said rings being circumferentially offset.
2. The assembly of claim 1, wherein:
- said segments at different diameters have different lengths.
3. The assembly of claim 1, wherein:
- said gaps are circumferentially offset as much as 12 degrees.
4. The assembly of claim 1, wherein:
- said gaps are axially as long as said segments.
5. The assembly of claim 1, wherein:
- said segments comprise free ends that bend when coming in contact with the borehole.
6. The assembly of claim 1, wherein:
- said extending segments have a free end initially radially offset from an external surface of said ring and axially aligned with the axis of said ring.
7. The assembly of claim 1, wherein:
- said multiple diameters comprise 2-4 diameters.
8. The assembly of claim 1, wherein:
- said ring comprises an internal groove to retain a seal against the mandrel and the sealing element.
9. The assembly of claim 1, wherein:
- said segments at different diameters have equal lengths.
10. The assembly of claim 1, wherein:
- said gaps are axially shorter than said segments.
Type: Application
Filed: Apr 13, 2017
Publication Date: Oct 18, 2018
Applicant: BAKER HUGHES INCORPORATED (Houston, TX)
Inventors: Andrew J. Cayson (Cypress, TX), Alexander M. Kendall (Houston, TX), Guijun Deng (The Woodlands, TX)
Application Number: 15/486,621