Patent Description:
It is sometimes desirable to be able to retrieve a well tool from a well. In such circumstances, it is desirable for the well tool to have an outer size that is smaller than any obstructions or restrictions through which the well tool must pass while it is being retrieved.

Some well tools, such as well barriers (packers, plugs, hangers, etc.) are expanded in operation in a well. If the well tool has been expanded downhole, it can be difficult to retrieve the tool through the obstructions or restrictions.

It will, thus, be readily appreciated that improvements are continually needed in the arts of constructing and utilizing tools for use in subterranean wells.

<CIT> discloses a well barrier over which the invention is characterised.

Disclosed herein are examples of an anti-extrusion backup system that expands when set and collapses or retracts when unset. This anti-extrusion backup system is very easy to retrieve from mono-bore wells and through wellbore restrictions. This anti-extrusion backup system is suitable for high pressure and high temperature well barriers (such as, bridge plugs, packers, liner hangers, etc.).

The anti-extrusion backup system addresses the problem of extrusion in some examples by using overlapping foldback rings that are slotted or perforated in anti-extrusion backups. The foldback rings are seated against a sliding sleeve that is pre-energized in its initial position, with enough force to reposition the foldback rings to their initial position after use.

When the barrier is set downhole, the foldback rings are deformed to act as a backup to the sealing elements, and the foldback rings are supported by the sliding sleeve and a fixed gage connector. The sleeve slides over the connector and compresses a spring stack, so that the sliding sleeve is fully-energized in its set position.

Surface areas of the gage connector and sliding sleeve provide enough support for the foldback rings during operation. When the barrier is unset, the energized sleeve slides over the fixed gage connector and shifts the foldback rings to a retracted retrieve position, typically below gage (but in some cases could be slightly above gage or at gage).

The sliding sleeve can slide over the foldback rings when they are below gage, or shift the foldback rings to a retrieve position. Note that the sliding sleeve can also be pushed or pulled in position by various different means (i.e., not necessarily a spring stack).

The accompanying drawings depict examples of the anti-extrusion backup system used on a well barrier in set and unset configurations. Certain drawings depict an example in run-in (or run in hole "RIH"), set, equalized and unset configurations. In some of these examples, the foldback rings are extended radially outward when the seal elements are compressed to set the barrier, and the foldback rings are retracted inward by the sliding sleeve when the barrier is unset.

Representatively illustrated in <FIG> is a system <NUM> for use with a subterranean well, and an associated method, which can embody principles of this disclosure. However, it should be clearly understood that the system <NUM> and method are merely one example of an application of the principles of this disclosure in practice, and a wide variety of other examples are possible. Therefore, the scope of this disclosure is not limited at all to the details of the system <NUM> and method described herein and/or depicted in the drawings.

In the system <NUM> depicted in <FIG>, a wellbore <NUM> is lined with casing <NUM> and cement <NUM>. The wellbore <NUM> is generally vertical and extends into an earth formation <NUM>.

In other examples, the wellbore <NUM> may be uncased or open hole in locations in which the principles of this disclosure are practiced. The wellbore <NUM> could be generally horizontal or otherwise inclined from vertical. Thus, the scope of this disclosure is not limited to any of the details of the components of the system <NUM> or the well with which they are used.

In the <FIG> example, a well barrier <NUM> is connected as part of a tubular string <NUM> positioned in the wellbore <NUM>. The well barrier <NUM> is used to prevent flow through all or a portion of the wellbore <NUM>, for example, in order to isolate sections of the wellbore from each other.

The well barrier <NUM> depicted in <FIG> is of the type known to those skilled in the art as a tubing retrievable packer, but other types of well barriers (such as, bridge plugs, frac plugs, liner hangers, etc.) may be used in other examples. In addition, it is not necessary for the well barrier <NUM> to be conveyed into or retrieved from the wellbore <NUM> using the tubular string <NUM> (for example, the well barrier could instead be conveyed and/or retrieved using wireline, slick line, coiled tubing or other type of conveyance). Thus, the scope of this disclosure is not limited to use of any particular type of well barrier, any particular type of conveyance, or to any particular details of the well barrier <NUM> as described herein or depicted in the drawings.

The well barrier <NUM> is configured to seal off an annulus <NUM> formed radially between the tubular string <NUM> and the wellbore <NUM>. For this purpose, the well barrier <NUM> includes a radially outwardly extendable seal section <NUM>. As described more fully below, the seal section <NUM> includes a seal element that can extend radially outward into sealing contact with an inner wall of the casing <NUM>. If the wellbore <NUM> is uncased, the seal element can sealingly engage a wall of the earth formation <NUM>.

The well barrier <NUM> in this example also includes an anchor or slip section <NUM>. The slip section <NUM> secures the well barrier <NUM> against displacement relative to the wellbore <NUM>. For example, the slip section <NUM> can enable the well barrier <NUM> to support loads applied to the well barrier from above or below, and the slip section can resist displacement due to a pressure differential applied across the seal section <NUM>.

As depicted in <FIG>, a flow passage <NUM> extends longitudinally through the well barrier <NUM> and tubular string <NUM>. In other examples, the flow passage <NUM> may not extend through the well barrier <NUM> (for example, if the well barrier is a bridge plug, etc.).

Referring additionally now to <FIG>, cross-sectional views of an example of the seal section <NUM> is representatively illustrated, apart from the system <NUM> and a remainder of the well barrier <NUM>. Note that the seal section examples <NUM> described herein and depicted in the drawings may be used with other well barriers and in other systems, in keeping with the principles of this disclosure.

The seal section <NUM> depicted in <FIG> is configured to be positioned on an inner mandrel <NUM> of the well barrier <NUM> (not shown in <FIG>, see <FIG>). In this example, the seal section <NUM> includes multiple annular seal elements <NUM> positioned longitudinally between two gage connectors or abutments <NUM>. The seal elements <NUM> are configured so that they will extend radially outward when the seal elements are longitudinally compressed between the abutments <NUM>.

The abutments <NUM> are connected to respective upper and lower connectors <NUM>. The connectors <NUM> control the positions of the abutments <NUM>, for example, enabling a distance between the abutments to be decreased (to thereby longitudinally compress the seal elements <NUM> between the abutments), and
enabling the distance between the abutments to be increased (to thereby radially inwardly retract the seal elements).

In some examples, the abutments <NUM> and connectors <NUM> may not be separate components, but could instead be integrally formed. Thus, the scope of this disclosure is not limited to use of any particular components, combination of components, or arrangement or configuration of components in the seal section <NUM>.

The seal section <NUM> depicted in <FIG> also includes anti-extrusion backups <NUM>. The anti-extrusion backups <NUM> operate to completely or partially fill a radial gap (e.g., the annulus <NUM> in the <FIG> system <NUM>) between the well barrier <NUM> and the surface against which the seal elements <NUM> seal. This helps to prevent or minimize any extrusion of the seal elements <NUM> through the gap due to a pressure differential across the seal elements.

In <FIG>, the seal section <NUM> is in an unset configuration. The seal elements <NUM> are not radially extended.

In <FIG>, the seal section <NUM> is in a set configuration. The longitudinal distance between the abutments <NUM> is decreased (as compared to <FIG>), and the seal elements <NUM> are thereby longitudinally compressed and radial outwardly extended.

Note that the anti-extrusion backups <NUM> are also radially outwardly extended in the <FIG> set configuration. The anti-extrusion backups <NUM> preferably, but not necessarily, contact the surface against which the seal elements <NUM> seal in the set configuration.

When it is desired to unset the well barrier <NUM> and retrieve it from the wellbore <NUM>, the seal section <NUM> can be essentially returned to its <FIG> configuration. In this manner, the well barrier <NUM> can be retrieved through any restrictions, obstructions, etc., through which it previously passed prior to being set.

To unset the well barrier <NUM>, the longitudinal distance between the abutments <NUM> is increased. This allows the seal elements <NUM> to elongate and radially inwardly retract out of engagement with the surface against which it previously sealed.

The anti-extrusion backups <NUM> are radially inwardly retracted in this example by use of a biasing device <NUM> and sleeve <NUM> to apply a biasing force against a radially outward portion of each backup. This causes the backup <NUM> to rotate toward the adjacent seal element <NUM> as it radially retracts, so that the backup retracts along with the seal element.

Referring additionally now to <FIG>, a more detailed cross-sectional view of this example of the backup <NUM>, the biasing device <NUM> and the sleeve <NUM> is representatively illustrated in the set configuration. In this example, the abutment <NUM> is displaced downward toward the seal element <NUM> when the well barrier <NUM> is set. This compresses the backup <NUM> between the abutment <NUM> and the seal element <NUM>, causing an intermediate portion of the backup to rotate so that it extends radially outward.

As depicted in <FIG>, a radially inward portion <NUM> of the backup <NUM> is secured to the abutment <NUM>, so that the radially inward portion displaces (or remains motionless) with the abutment. A radially outward portion <NUM> of the backup <NUM> is able to displace longitudinally somewhat relative to the radially inward portion <NUM> and the abutment <NUM>. Thus, the backup <NUM> can rotate between the radially inward and radially outward portions <NUM>, <NUM>.

In this example, the anti-extrusion backup <NUM> includes an annular-shaped fold-back ring <NUM>. The fold-back ring <NUM> facilitates return of the anti-extrusion backup <NUM> to its radially retracted unset configuration (see <FIG>). In some examples, the fold-back ring <NUM> can be stiffer than the intermediate portion of the anti-extrusion backup <NUM> between the radially inward and radially outward portions <NUM>, <NUM>, so that the fold-back ring helps the anti-extrusion backup to maintain its shape as it transitions from the set to the unset configuration.

Note that the sleeve <NUM> radially outwardly surrounds the abutment <NUM> and is positioned to apply a biasing force to the radially outward portion <NUM> of the backup <NUM>. In the <FIG> example, the fold-back ring <NUM> is configured with a shoulder <NUM> for secure engagement with an end of the sleeve <NUM> in both of the set and unset configurations.

As depicted in <FIG>, the biasing force exerted by the biasing device <NUM> via the sleeve <NUM> to the anti-extrusion backup <NUM> has caused the backup to rotate to its retracted unset configuration. Preferably, the anti-extrusion backup <NUM> and the seal element <NUM> have an outer diameter that is no greater than that of a gage diameter of the well barrier <NUM> (such as, a maximum outer diameter of the sleeve <NUM>) in the unset configuration.

In this example, the sleeve <NUM> contacts the anti-extrusion backup <NUM> in both the set and unset configurations. The biasing device <NUM> may be pre-loaded, so that a biasing force is exerted against the radially outward portion <NUM> of the backup <NUM> in the unset configuration. The biasing force may be increased as the sleeve <NUM> displaces relative to the abutment <NUM> to the set configuration. This increased biasing force may then be used to rotate the backup <NUM> back to its retracted unset configuration when it is desired to retrieve the well barrier <NUM>.

The biasing device <NUM> in this example comprises a stack of Belleville spring washers. In other examples, the biasing device <NUM> could comprise another type of spring, an elastomer, a piston and pressurized chamber, or any other device capable of applying a resilient biasing force to the anti-extrusion backup <NUM>.

In the initial unset configuration, a shear screw <NUM> releasably secures against relative displacement between the abutment <NUM> and the sleeve <NUM>. However, when the well barrier <NUM> is set, the shear screw is sheared, thereby permitting relative displacement between the abutment <NUM> and the sleeve <NUM>.

Referring additionally now to <FIG>, another example of the seal section <NUM> is representatively illustrated in respective unset and set configurations. In this example, the sleeve <NUM> is not used. Instead, the biasing device <NUM> applies the biasing force directly to the anti-extrusion backup <NUM>.

In addition, the fold-back ring <NUM> is not used in the anti-extrusion backup <NUM> of <FIG>. In <FIG>, it may be seen that the intermediate portion of the backup <NUM> is provided with perforations or slots <NUM> to make it more readily deformable. In other examples, the backup <NUM> could comprise overlapping radially extending flexible leaves, or another arrangement suitable for deforming from the unset to the set configuration, and then deforming from the set to the unset configuration.

The biasing device <NUM> in the <FIG> example comprises multiple Belleville spring washers stacked in a same orientation. In this manner, one of the spring washers is in contact with the intermediate portion of the anti-extrusion backup <NUM>.

In the <FIG> unset configuration, the biasing device <NUM> is radially retracted. Preferably, the biasing device <NUM> does not extent outward past a gage diameter of the well barrier <NUM>. If desired, a pre-load may be applied to the biasing device <NUM>, but preferably the pre-load will not cause the biasing device to extend outward past the gage diameter.

In the <FIG> set configuration, the backup <NUM> and the biasing device <NUM> have rotated somewhat, due to the longitudinal compression of the seal section <NUM>, so that the backup and the biasing device are radially outwardly extended. The abutments <NUM> are not shown in <FIG>, but it will be appreciated that the abutments <NUM> or another type of abutments, shoulders or gage rings can be used to apply a longitudinally compressive force to set the well barrier <NUM>. The longitudinally compressive force is removed when the well barrier <NUM> is unset.

When the longitudinally compressive force is removed, the biasing force exerted by the biasing device <NUM> against the radially outward portion of the backup <NUM> will cause the backup to rotate back to its radially retracted unset configuration (as depicted in <FIG>). The biasing device <NUM> (the individual spring washers) will also rotate back to their radially retracted unset configuration when the compressive force is removed.

Referring additionally now to <FIG>, another example of the seal section <NUM> is representatively illustrated in an unset configuration. In this example, the seal section <NUM> includes different anti-extrusion backups <NUM>. An upper abutment <NUM>, anti-extrusion backup <NUM>, biasing device <NUM> and sleeve <NUM> are depicted in <FIG>, and a lower abutment <NUM>, anti-extrusion backup <NUM>, biasing device <NUM> and sleeve <NUM> are depicted in <FIG>.

In the <FIG> example, the anti-extrusion backup <NUM> includes the fold-back ring <NUM>. The fold-back ring <NUM> has a frustoconical shape in this example and makes up a majority of the anti-extrusion backup <NUM>. A thinner backup ring <NUM> is interposed between the fold-back ring <NUM> and the seal element <NUM>. The backup ring <NUM> radially outwardly overlaps an end of the seal element <NUM>. The fold-back ring <NUM> radially outwardly overlaps most of the backup ring <NUM>.

Note that the radially inward portion <NUM> of the anti-extrusion backup <NUM> (including both of the fold-back ring <NUM> and the backup ring <NUM>) is secured to the abutment <NUM> in this example. This ensures that the radially outward portion <NUM> of the anti-extrusion backup <NUM> will be rotated radially inward by the biasing force exerted by the biasing device <NUM> when the well barrier <NUM> is unset.

In the <FIG> example, an additional fold-back ring <NUM> is used. The fold-back ring <NUM> is interposed between the backup ring <NUM> and the fold-back ring <NUM>.

The shoulder <NUM> is formed in the fold-back ring <NUM>. Radially inward portions of the fold-back rings <NUM>, <NUM> and the backup ring <NUM> are all secured to the abutment <NUM>.

Referring additionally now to <FIG>, another example of the seal section <NUM> is representatively illustrated, in respective unset and set configurations. In this example, the anti-extrusion backup <NUM> is similar to the <FIG> example, in that it includes the multiple fold-back rings <NUM>, <NUM> as well as the backup ring <NUM>.

Referring additionally now to <FIG>, another example of the seal section <NUM> is representatively illustrated, in respective unset and set configurations. In this example, the anti-extrusion backup <NUM> extends radially outward and the biasing device <NUM> is compressed when the well barrier <NUM> is set as depicted in <FIG>. The anti-extrusion backup <NUM> radially retracts, due to the compressed biasing device <NUM>, when the well barrier <NUM> is unset as depicted in <FIG>.

Referring additionally now to <FIG>, another example of the well barrier <NUM> is representatively illustrated in run-in, set, equalized and released or unset configurations. Only an upper portion of the well barrier <NUM> including the seal section <NUM> is depicted in <FIG>. In this example, the anti-extrusion backups <NUM> are similar to that depicted in <FIG>.

In the run-in configuration of <FIG>, the well barrier <NUM> is suited to be conveyed into a wellbore or tubular string, which in some cases can include restrictions or obstructions. Accordingly, the seal section <NUM> is radially retracted, with the seal elements <NUM> and anti-extrusion backups <NUM> preferably at or below a gage diameter of the well barrier <NUM>.

In the set configuration of <FIG>, the longitudinal distance between the abutments <NUM> is decreased, so that the seal elements <NUM> are longitudinally compressed and radially outwardly extended. The anti-extrusion backups <NUM> are also radially outwardly extended, and the biasing device <NUM> is further compressed to thereby increase the biasing force exerted on the sleeve <NUM> (and the radially outward portion <NUM> of the backup <NUM>).

In the equalized configuration of <FIG>, any pressure differential across the seal elements <NUM> is relieved, in preparation for unsetting the well barrier <NUM>. As depicted in <FIG>, the seal elements <NUM> and anti-extrusion backups <NUM> remain radially outwardly extended.

In the unset configuration of <FIG>, the longitudinal distance between the abutments <NUM> is increased, thereby permitting the seal elements <NUM> to radially inwardly retract. In addition, the biasing forces exerted against the upper portions <NUM> of the anti-extrusion backups <NUM> (see <FIG>) has caused the backups to rotate inward to their radially retracted positions. The well barrier <NUM> can now be conveniently retrieved, including through any restrictions or obstructions through which it may have previously been conveyed.

Referring additionally now to <FIG>, another example of the seal section <NUM> is representatively illustrated in respective unset and set configurations. In this example, the anti-extrusion backups <NUM> are similar to that depicted in <FIG>.

In the <FIG> unset configuration, the seal elements <NUM> and the backups <NUM> are radially retracted. In the <FIG> set configuration, the seal elements <NUM> and the backups <NUM> are radially extended, due to longitudinal compression of the seal section <NUM>.

In the precess of transitioning from the unset to the set configuration, the backup <NUM> rotates outward (the radially outward portion <NUM> rotates outward relative to the radially inward portion <NUM>, which is secured to the abutment <NUM>). In the process of transitioning from the set to the unset configuration, the backup <NUM> rotates inward (the radially outward portion <NUM> rotates inward relative to the radially inward portion <NUM>, which is secured to the abutment <NUM>), due to the biasing force exerted by the biasing device <NUM>.

It may now be fully appreciated that the above disclosure provides significant advancements to the art of constructing and utilizing well barriers for subterranean wells. In some examples described herein, the well barrier <NUM> includes features that enable the anti-extrusion backup <NUM> to be radially retracted (for example, to its initial unset configuration) prior to retrieving the well barrier from a well.

The above disclosure provides to the art a well barrier <NUM>. In one example, the well barrier <NUM> can include an annular seal element <NUM>, an anti-extrusion backup <NUM> having radially inward and radially outward portions <NUM>, <NUM>, and a biasing device <NUM> that exerts a biasing force against the radially outward portion <NUM> of the anti-extrusion backup <NUM>.

In any of the examples described herein, the well barrier <NUM> may include an abutment <NUM>. The radially inward portion <NUM> of the anti-extrusion backup <NUM> may be secured against longitudinal displacement relative to the abutment <NUM>.

In any of the examples described herein, the radially outward portion <NUM> of the anti-extrusion backup <NUM> may be longitudinally displaceable relative to the abutment <NUM>.

In any of the examples described herein, the anti-extrusion backup <NUM> may retract radially inward in response to the biasing force applied to the radially outward portion <NUM> of the anti-extrusion backup <NUM>.

In any of the examples described herein, the biasing device <NUM> may comprise at least one Belleville spring washer.

In any of the examples described herein, the biasing device <NUM> may exert the biasing force against a sleeve <NUM> reciprocably disposed relative to the anti-extrusion backup <NUM>.

In any of the examples described herein, the sleeve <NUM> may be reciprocably disposed relative to an abutment <NUM>, the seal element <NUM> may extend radially outward in response to a compressive force applied between the abutment <NUM> and the seal element <NUM>, and the sleeve <NUM> may surround the abutment <NUM>.

In any of the examples described herein, the anti-extrusion backup <NUM> may include a fold-back ring <NUM>. The fold-back ring <NUM> may retract radially inward in response to application of the biasing force to the radially outward portion <NUM> of the anti-extrusion backup <NUM>.

The above disclosure also provides to the art a method of operating a well barrier <NUM>. In one example, the method can include: setting the well barrier <NUM> by decreasing a longitudinal distance between first and second abutments <NUM> of the well barrier <NUM>, thereby compressing a seal element <NUM> between the first and second abutments <NUM>; and unsetting the well barrier <NUM> by increasing the longitudinal distance between the first and second abutments <NUM>. The unsetting step includes radially inwardly retracting an anti-extrusion backup <NUM> positioned longitudinally between the seal element <NUM> and the first abutment <NUM>.

In any of the examples described herein, the anti-extrusion backup <NUM> may expand radially outward in response to the compressing of the seal element <NUM>.

In any of the examples described herein, the retracting step can include applying a biasing force to a radially outward portion <NUM> of the anti-extrusion backup <NUM>.

In any of the examples described herein, the biasing force applying step may include a biasing device <NUM> biasing a sleeve <NUM> to displace relative to the first abutment <NUM> and toward the seal element <NUM>.

In any of the examples described herein, the sleeve <NUM> may surround the first abutment <NUM>.

In any of the examples described herein, the setting step may include displacing the sleeve <NUM> relative to the first abutment <NUM> in a first direction, and the unsetting step may include displacing the sleeve <NUM> relative to the first abutment <NUM> in a second direction opposite to the first direction.

In any of the examples described herein, the setting step may include increasing the biasing force.

In any of the examples described herein, the setting step may include rotating a portion of the anti-extrusion backup <NUM> in a first direction, and the unsetting step may include rotating the portion of the anti-extrusion backup <NUM> in a second direction opposite to the first direction.

Also described above is another well barrier <NUM>. In this example, the well barrier <NUM> can include an annular seal element <NUM>, an anti-extrusion backup <NUM>, an abutment <NUM> displaceable relative to the seal element <NUM> to compress the seal element <NUM>, a sleeve <NUM> reciprocable relative to the abutment <NUM>, and a biasing device <NUM> that biases the sleeve <NUM> toward the anti-extrusion backup <NUM>.

In any of the examples described herein, a radially inward portion <NUM> of the anti-extrusion backup <NUM> may be secured relative to the abutment <NUM>.

In any of the examples described herein, the biasing device <NUM> may bias the sleeve <NUM> into contact with a radially outward portion <NUM> of the anti-extrusion backup <NUM>.

In any of the examples described herein, the anti-extrusion backup <NUM> may retract radially inward in response to a biasing force applied via the sleeve <NUM> to the radially outward portion <NUM> of the anti-extrusion backup <NUM>.

In any of the examples described herein, the anti-extrusion backup <NUM> may include a fold-back ring <NUM>. The fold-back ring <NUM> may retract radially inward in response to application of a biasing force to a radially outward portion <NUM> of the anti-extrusion backup <NUM>.

Although various examples have been described above, with each example having certain features, it should be understood that it is not necessary for a particular feature of one example to be used exclusively with that example. Instead, any of the features described above and/or depicted in the drawings can be combined with any of the examples, in addition to or in substitution for any of the other features of those examples. One example's features are not mutually exclusive to another example's features. Instead, the scope of this disclosure encompasses any combination of any of the features.

Although each example described above includes a certain combination of features, it should be understood that it is not necessary for all features of an example to be used. Instead, any of the features described above can be used, without any other particular feature or features also being used.

It should be understood that the various embodiments described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of this disclosure. The embodiments are described merely as examples of useful applications of the principles of the disclosure, which is not limited to any specific details of these embodiments.

In the above description of the representative examples, directional terms (such as "above," "below," "upper," "lower," etc.) are used for convenience in referring to the accompanying drawings. However, it should be clearly understood that the scope of this disclosure is not limited to any particular directions described herein.

The terms "including," "includes," "comprising," "comprises," and similar terms are used in a non-limiting sense in this specification. For example, if a system, method, apparatus, device, etc., is described as "including" a certain feature or element, the system, method, apparatus, device, etc., can include that feature or element, and can also include other features or elements. Similarly, the term "comprises" is considered to mean "comprises, but is not limited to.

Claim 1:
A well barrier (<NUM>), comprising:
an annular seal element (<NUM>);
an anti-extrusion backup (<NUM>);
an abutment (<NUM>) displaceable relative to the seal element to compress the seal element characterised in that the well barrier further comprises a sleeve (<NUM>) reciprocable relative to the abutment; and
a biasing device (<NUM>) that biases the sleeve toward the anti-extrusion backup.