CN117500998A - Annular barrier - Google Patents

Abstract

The present invention relates to an annular barrier for providing zone isolation downhole in an annulus between a metal well tubular structure and another metal well tubular structure or a borehole wall, comprising: a tubular metal part configured to be installed as part of a metallic well tubular structure, the tubular metal part having an outer surface, an opening and an axial extension direction along the metallic well tubular structure; and an expandable metal sleeve surrounding the tubular metal member, the first expandable metal sleeve having a circumferential groove, a first end and a second end, each end of the expandable metal sleeve being connected to an outer surface of the tubular metal member, wherein the annular barrier further comprises an anchor arranged in the circumferential groove, the anchor comprising a first anchor member at least partially overlapping the second anchor member in a radial direction perpendicular to the axial extension direction such that an inner surface of the first anchor member at least partially abuts an outer surface of the second anchor member. Furthermore, the present invention relates to a downhole completion system.

Description

Annular barrier

Technical Field

The present invention relates to an annular barrier for providing zone isolation downhole in an annulus between a metal well tubular structure and another metal well tubular structure or a borehole wall. Furthermore, the present invention relates to a downhole completion system.

Background

An annular barrier is used downhole to provide isolation of one zone from another zone in the borehole annulus between a metal well tubular structure and a borehole wall or another metal well tubular structure. The temperature may change when the annular barrier has been set, for example when the expandable metal sleeve has been expanded. Thus, if the temperature increases, the length of the metal well tubular structure with the annular barrier will increase, as well as if the temperature decreases, the length of the metal well tubular structure will decrease, e.g. during fracturing with seawater. During such a change in length the axial load on the expandable metal sleeve will change and experiments have shown that the annular barrier cannot withstand high axial loads when the pressure difference across the expandable metal sleeve is low, i.e. when the pressure inside the annular barrier is low compared to the pressure in the annulus.

Disclosure of Invention

It is an object of the present invention to wholly or partly overcome the above-mentioned disadvantages and shortcomings of the prior art. More particularly, it is an object to provide an improved annular barrier which is capable of withstanding higher axial loads than known annular barriers when the pressure difference across the expandable metal sleeve of the annular barrier is low.

The above objects, together with numerous other objects, advantages, and features, which will become evident from below description, are accomplished by a solution in accordance with the present invention by an annular barrier for providing zone isolation downhole in an annulus between a metal well tubular structure and another metal well tubular structure or a borehole wall, the annular barrier comprising:

-a tubular metal part mounted as part of a metallic well tubular structure, the tubular metal part having an outer surface, an opening and an axial extension direction along the metallic well tubular structure; and

an expandable metal sleeve surrounding the tubular metal member, the first expandable metal sleeve having a circumferential groove, a first end and a second end, each end of the expandable metal sleeve being connected to an outer surface of the tubular metal member,

wherein the annular barrier further comprises an anchor arranged in the circumferential groove, the anchor comprising a first anchor part and a second anchor part, the first anchor part at least partially overlapping the second anchor part in a radial direction perpendicular to the axial extension direction such that an inner surface of the first anchor part at least partially abuts an outer surface of the second anchor part.

Further, the anchors may be circumferential anchors.

Furthermore, the inner surface of the first anchor part and the outer surface of the second anchor part may be inclined with respect to the axial extension direction.

By tilting the inner surface of the first anchoring member and the outer surface of the second anchoring member relative to the axial extension direction, when at least a part of the expandable metal sleeve is moved in one direction along the axial direction, the first anchoring member is moved in the opposite direction along the tilted outer surface of the second anchoring member, and then the first anchoring member is forced radially outwards, thereby anchoring the expandable metal sleeve even further to another metal well tubular structure or borehole wall.

Furthermore, the first and second anchor parts may be one integral/unitary piece.

Furthermore, the first and second anchor parts may be one integral piece, the first and second anchor parts forming a key ring, wherein the first anchor part is one end of the key ring and the second anchor part is the other end of the key ring.

Furthermore, the first anchoring member may be formed as one integral/unitary piece and the second anchoring member as another integral/another unitary piece.

Further, the first anchor component may be shaped as a first split ring and the second anchor component shaped as a second split ring. Thus, the first anchoring member may comprise a slit/opening.

Furthermore, the anchor may further comprise a fixation unit arranged in a groove of the first anchoring part.

Furthermore, the fixation unit may comprise an annular member extending all the way/full-circle around the expandable metal sleeve, each end of the annular member being connected with the frangible element.

Furthermore, the annular part may be a sealing element, wherein each end portion of the sealing element is connected in at least one connecting part.

Furthermore, the frangible element may be a pin extending through the at least one connection member and into the first anchor member.

Furthermore, the first anchoring member may comprise a recess in which both the sealing element and the fixation element are arranged.

Furthermore, the first anchoring part may comprise two grooves, the sealing element being arranged in one of the grooves and the fixing element being arranged in the other groove.

Furthermore, the first anchoring member may comprise at least one groove having a trapezoidal cross-sectional shape along the axial extension direction.

Furthermore, the groove may have a first length along the axial extension direction and the first anchoring member may have a second length along the axial extension direction, wherein the first length is at least 10% of the second length, and preferably at least 20% of the second length.

Furthermore, the annular barrier may further comprise a connection element arranged between the tubular metal part and the expandable metal sleeve, and the connection element may be connected with the tubular metal part and the expandable metal sleeve.

Furthermore, the expandable metal sleeve may be divided into at least two parts, and each part may be connected to the connecting element.

Furthermore, the connecting element may be arranged opposite the circumferential groove.

Furthermore, the first anchoring part may further comprise an outer surface, the second anchoring part comprises an inner surface, and the outer surface of the first anchoring part comprises friction enhancing means and faces the further well tubular metal structure or the borehole wall.

Further, the friction enhancing mechanism may be a pointed portion or a groove.

Furthermore, the outer surface of the first anchoring part may have at least one groove in which the spring element or the sealing element is arranged.

Furthermore, the inner surface of the second anchoring member may have at least one groove in which the spring element or the sealing element is arranged.

Further, the friction between the inner surface of the first anchor component and the outer surface of the second anchor component may be less than the friction between the inner surface of the second anchor component and the circumferential groove.

Furthermore, the inner surface of the second anchoring member may have at least one groove in which the spring element or the sealing element is arranged.

Further, the sealing member may be ring-shaped having a trapezoidal cross-sectional shape.

Further, the anchor may include a third anchor member having an outer surface abutting the second inner surface of the first anchor member such that the first anchor member is disposed between the third anchor member and the second anchor member, and the inner surfaces of the third anchor member and the second anchor member face and abut the circumferential groove.

Furthermore, the outer surface of the third anchor member may be inclined in an opposite direction, i.e. in a direction opposite to the direction in which the outer surface of the second anchor member is inclined.

Further, the second inner surface of the first anchor component may be inclined, thus corresponding to the inclined outer surface of the third anchor component.

According to the invention, the annular barrier may further comprise a second anchor comprising a first anchor part and a second anchor part, the first anchor part at least partly overlapping the second anchor part in a radial direction perpendicular to the axial extension direction such that an inner surface of the first anchor part at least partly abuts an outer surface of the second anchor part, the inner surface of the first anchor part and the outer surface of the second anchor part being inclined in opposite directions with respect to the axial extension direction, i.e. in opposite directions to the direction in which the inner surface of the first anchor part and the outer surface of the second anchor part of the first anchor part are inclined with respect to the axial extension direction.

Thus, the inner surface of the first anchor member of the first anchor may slope upward toward the top of the well and the inner surface of the first anchor member of the second anchor slopes downward away from the top of the well. By having a first anchor with an inner surface of the first anchoring part inclined in one direction and a second anchor with a surface of the first anchoring part inclined in the opposite direction, the annular barrier can withstand axial loads in both directions along the axial extension direction, since the first anchor is activated when axial loads are in one direction and the second anchor is activated when axial loads are pulled in the opposite direction.

Furthermore, the first anchor and the second anchor may be arranged in the same circumferential groove.

Furthermore, the expandable metal sleeve may have a second circumferential groove in which the sealing unit is arranged.

Furthermore, the sealing unit may comprise a sealing element made of, for example, an elastomer.

Furthermore, the sealing unit may comprise an annular support element and a key ring element.

Furthermore, the expandable metal sleeve may comprise at least two sealing units, between which the anchor is arranged.

Finally, the invention also relates to a downhole completion system comprising an annular barrier and a metal well tubular structure.

Drawings

The invention and its many advantages will be described in more detail below with reference to the attached schematic drawings, which for illustrative purposes only show some non-limiting embodiments, wherein:

figure 1 shows a cross-sectional view of an annular barrier with a sealing unit and an anchor;

figure 2 shows a cross-sectional view of another annular barrier with anchors;

FIG. 3 shows a cross-sectional view of a portion of an expandable metal sleeve having a groove in which an anchor is disposed;

FIG. 4 shows a cross-sectional view of a portion of another expandable metal sleeve having a recess in which another spring-loaded anchor is disposed;

fig. 5 shows a cross-sectional view of a portion of another annular barrier in an expandable metal sleeve having a recess in which another spring-loaded anchor is disposed;

FIG. 6 shows a cross-sectional view of a portion of another expandable metal sleeve having a recess in which another anchor is disposed, the anchor having an oblique direction opposite to the direction in which the anchor shown in FIG. 3 is disposed;

FIG. 7 shows a cross-sectional view of a portion of yet another expandable metal sleeve having grooves, wherein another anchor includes first, second and third anchor members;

FIG. 8 shows a cross-sectional view of a portion of yet another expandable metal sleeve having grooves, wherein another anchor includes first, second and third anchor components and springs in each component;

FIG. 9 is a schematic illustration of the relationship of axial load on an annular barrier to differential pressure across an expandable metal sleeve;

FIG. 10 shows a cross-sectional view of a portion of another expandable metal sleeve having a groove in which another anchor with a sealing element is disposed;

FIG. 11 shows a cross-sectional view of a portion of yet another expandable metal sleeve having a groove in which another anchor with a sealing element is disposed;

fig. 12 shows a cross-sectional view of a portion of yet another expandable metal sleeve having a groove in which another anchor with a sealing unit is disposed;

FIG. 13 shows a cross-sectional view of a portion of yet another expandable metal sleeve having a groove in which another anchor having a spring and sealing element is disposed;

figure 14 shows a perspective view of a portion of an annular barrier with another anchor;

FIG. 15 shows a cross-sectional view of a portion of yet another expandable metal sleeve having an anchor with a fixation element incorporated into a sealing unit;

FIG. 16 shows a cross-sectional view of a portion of yet another expandable metal sleeve having an anchor with a fixation element and a separate sealing unit therein;

FIG. 17 shows a cross-sectional view of a portion of yet another expandable metal sleeve having a recess in which two opposing anchors are disposed;

FIG. 18A shows a cross-sectional view of a portion of yet another unexpanded, expandable metal sleeve having a recess in which an anchor including two second anchor members is disposed; and

fig. 18B shows the expandable metal sleeve of fig. 18A in an expanded state.

All the figures are highly schematic and not necessarily to scale, and they show only those parts which are necessary in order to elucidate the invention, other parts being omitted or merely suggested.

Detailed Description

Fig. 1 shows a cross-sectional view of an annular barrier 1 in an unexpanded state for providing zone isolation downhole in an annulus 2 between a metal well tubular structure 3 and another metal well tubular structure 3b as shown in fig. 2 or downhole in an annulus between a metal well tubular structure 3 and a wall portion 5 of a borehole 4 as shown in fig. 1. The annular barrier 1 comprises a tubular metal part 7, which tubular metal part 7 is mounted as part of the metal well tubular structure 3. The tubular metal part 7 has an outer surface 8, an opening 6 and a direction L of axial extension along the metallic well tubular structure 3. The annular barrier 1 comprises an expandable metal sleeve 9 surrounding a tubular metal part 7, wherein the first expandable metal sleeve 9 has a circumferential groove 10, a first end 11 and a second end 12, and each end of the expandable metal sleeve 9 is connected with the outer surface 8 of the tubular metal part 7. The annular barrier 1 further comprises an anchor 14 arranged in the circumferential groove 10, which anchor 14 comprises a first anchoring member 15 and a second anchoring member 16, which first anchoring member 15 at least partially overlaps the second anchoring member 16 in a radial direction perpendicular to the axial extension direction L, such that an inner surface 17 of the first anchoring member 15 at least partially abuts an outer surface 18 of the second anchoring member 16. The anchor 14 is a circumferential anchor that extends all the way around the expandable metal sleeve 9, and the anchor 14 may be open so that the anchor 14 may be mounted in the circumferential groove 10.

In order to provide enhanced anchoring during axial loading, the inner surface 17 of the first anchoring part 15 and the outer surface 18 of the second anchoring part 16 are inclined with respect to the axial extension direction L. Thus, when the temperature changes, at least a part of the expandable metal sleeve 9 is moved in one direction along the axial extension direction L as indicated by arrow a in fig. 3, the first anchoring member 15 is moved in the opposite direction along the inclined outer surface 18 of the second anchoring member 16 as indicated by arrow B in fig. 3, and the first anchoring member 15 is then pushed radially outwards as indicated by the broken line in fig. 3, thereby further anchoring the expandable metal sleeve 9 to the further metal well tubular structure 3B (as shown in fig. 2) or the wall portion 5 of the borehole 4.

In the graph of fig. 9, the axial load on the annular barrier 1 as a function of the pressure difference is shown in solid lines. By having an annular barrier 1 with anchors according to the invention, the axial load is not reduced when the pressure difference is as low as in prior art annular barriers (this is indicated by the dashed line).

In fig. 1, the first anchoring member 15 forms one integral/one piece and the second anchoring member 16 forms a second integral/one piece. The first anchoring member 15 is shaped as a first split ring and the second anchoring member 16 is shaped as a second split ring so that it can widen and thus fit in the circumferential groove 10. First, the second anchoring member 16 is widened and moved into the circumferential groove 10 along the outer surface 37 of the expandable metal sleeve 9, and then the first anchoring member 15 is widened and moved along the outer surface 37 of the expandable metal sleeve 9 until reaching the circumferential groove 10 and being arranged around the second anchoring member 16 such that the inclined inner surface 17 of the first anchoring member 15 and the inclined outer surface 18 of the second anchoring member 16 abut.

The first anchoring part 15 further comprises an outer surface 19 facing the other metal well tubular structure 3b as shown in fig. 2 or facing the wall part 5 of the borehole 4 as shown in fig. 1, and the second anchoring part 16 comprises an inner surface 20 facing and abutting the circumferential groove 10. The outer surface 19 of the first anchor component 15 comprises friction enhancing means 21, such as spikes/nibs 21a as shown in fig. 1, and/or is provided with grooves 21b as shown in fig. 2.

In fig. 1, the annular barrier 1 further comprises a second anchor 14b, the second anchor 14b comprising a first anchor part 15b and a second anchor part 16b, the first anchor part 15b having an outer surface 19b and being at least partially overlapping the second anchor part 16b in a radial direction perpendicular to the axial extension direction L, such that an inner surface 17b of the first anchor part 15b at least partially abuts an outer surface 18b of the second anchor part 16 b. The inner surface 17b of the first anchoring member 15b and the outer surface 18b of the second anchoring member 16b are inclined in opposite directions with respect to the axial extension direction L, i.e. in opposite directions to the direction of the first anchor 14. The first anchor 14 has an inclined face which corresponds to the inclined face of the second anchor 14b when mirrored about the line R. As shown in fig. 1, by having the first anchor 14 with an inclined surface in one direction and the second anchor 14b with an inclined surface in the opposite direction, the annular barrier 1 can withstand axial loads in both directions along the axial extension direction L, because the first anchor 14 is activated when the axial load is in one direction and the second anchor 14b is activated when the axial load is pulled in the opposite direction.

The expandable metal sleeve 9 of the annular barrier 1 has a second circumferential groove 10b in which the sealing unit 24 is arranged. The sealing unit 24 comprises a sealing element 25 made of e.g. an elastomer or a polymer, an annular support element 26 on each side of the sealing element 25, and a key ring-shaped element 27 surrounding a part of the annular support element 26. The expandable metal sleeve 9 comprises a plurality of sealing units 24 and each anchor 14, 14b is arranged between two sealing units 24.

In fig. 2, the first anchoring member 15 and the second anchoring member 16 are one integral piece. The first anchor member 15 and the second anchor member 16 form a key ring 34, wherein the first anchor member 15 is one end of the key ring 34 and the second anchor member 16 is the other end of the key ring 34. When the expandable metal sleeve 9 is expanded, the key ring 34 unwinds and when expanded, the first anchoring member 15 will not fully overlap the second anchoring member 16 along the entire circumference of the expandable metal sleeve 9.

In fig. 2, the expandable metal sleeve 9 has a plurality of grooves 10, 10b, and between these grooves other "empty" grooves are provided, so that the anchors 14, 14b and the sealing unit 24 are arranged with the same distance between them along the axial extension direction L.

Each end of the expandable metal sleeve 9 is connected to the outer surface 8 of the tubular metal part 7, for example by means of a connecting part 38 and/or by welding, as shown in fig. 1. In fig. 2, the annular barrier 1 further comprises a valve assembly 33 in fluid connection with the opening 6 and the expandable space 28, so as to fluidly connect the opening 6 and the expandable space 28 during expansion of the expandable metal sleeve 9, and to close the fluid connection after the expandable metal sleeve 9 has been properly expanded. The valve assembly 33 may be opened in a second position for fluid connection between the annulus 2 and the expandable space 28 in order to equalize the pressure therebetween.

To enhance the initial anchoring, the outer surface 19 of the first anchoring member 15 has two grooves 23, the spring element 22 being arranged in the grooves 23, as shown in fig. 4. During expansion of the expandable metal sleeve 9, the spring element 22 is compressed and after expansion is completed, the spring element 22 will decompress slightly due to the small "spring back effect" of the expanded metal. The spring element 22 will thus always be in contact with the wall portion 5 of the borehole 4, and when axial loading begins, the spring element 22 will ensure that the first anchor part 15 moves along the inclined outer surface 18 of the second anchor part 16, and thus the first anchor part 15 will be pushed radially outwards, as indicated by the broken line in fig. 3. Another way is shown in fig. 5, wherein the inner surface 20 of the second anchoring part 16 has two grooves 23, the spring element 22 being arranged in the grooves 23. When the spring element 22 is arranged in the inner surface 20, the spring element 22 urges the second anchor part 16 and the first anchor part 15 to move outwards such that the first anchor part 15 is in contact/engagement with the wall part 5 of the borehole 4 or another metal well tubular structure 3 b.

There is low friction between the inner surfaces 17, 17b of the first anchor parts 15, 15b and the outer surfaces 18, 18b of the second anchor parts 16, 16b, so that a large amount of force is not lost to slide the anchor parts relative to each other. Thus, the friction between the inner surfaces 17, 17b of the first anchoring members 15, 15b and the outer surfaces 18, 18b of the second anchoring members 16, 16b is smaller than the friction between the inner surfaces 20, 20b of the second anchoring members 16, 16b and the circumferential groove 10.

In fig. 3-5, the circumferential groove 10 has an inclined end face 35, and in fig. 6-8, the end face 35 is perpendicular to the axial extension direction L. When having a perpendicular end face 35, as shown in fig. 6-8, the second anchor component 16 is more constrained than in fig. 3-5. The inclined outer surface 18 of the second anchor part 16 ends at the top of the circumferential groove 10 such that the first anchor part 15 is not limited by the end face 35 of the groove 10 and is therefore not prevented from sliding further over the end of the outer surface 18 of the second anchor part 16 when required.

In fig. 7 and 8, the anchor 14 of the annular barrier 1 comprises a third anchoring member 31, which third anchoring member 31 has an outer surface 32 abutting the second inner surface 17a of the first anchoring member 15, such that the first anchoring member 15 is arranged between the third anchoring member 31 and the second anchoring member 16, and the inner surface 36 of the third anchoring member 31 and the inner surface 20 of the second anchoring member 16 face and abut the circumferential groove 10. In fig. 8, the outer surface 19 of the first anchor part 15 comprises two grooves 23 in which the spring elements 22 are arranged, and the inner surface 20 of the second anchor part 16 and the inner surface 36 of the third anchor part 31 both comprise two grooves 23 in which the spring elements 22 are arranged.

Another way of enhancing the initial anchoring is shown in fig. 10-13, wherein the outer surface 19 of the first anchoring member 15 has a groove 23, and the sealing element 25a is arranged in the groove 23. The sealing member 25a is made of, for example, an elastomer or a polymer. During expansion of the expandable metal sleeve 9, the sealing element 25a is compressed and after expansion is completed, the sealing element 25a will decompress slightly due to the small "spring back effect" of the expanded metal. The sealing element 25a will thus always be in contact with the wall portion 5 of the wellbore 4, and when axial loading begins, the sealing element 25a will ensure that the first anchoring member 15 moves along the inclined outer surface 18 of the second anchoring member 16, and thus the first anchoring member 15 will be pushed radially outwards, as indicated by the broken line in fig. 3, and will provide sufficient anchoring to withstand the axial loading. In fig. 10, the expandable metal sleeve 9 comprises two protrusions 29, between which a circumferential groove 10 is formed, in which circumferential groove 10 the anchor 14 is arranged. The first anchor part 15 has a groove 23, a sealing element 25a is arranged in the groove 23, and the sealing element 25a is ring-shaped with a trapezoidal cross-sectional shape. In fig. 11, the projection 29 is somewhat thicker, i.e. it extends radially outwards compared to the projection 29 in fig. 10, and the sealing element 25a also extends beyond the cusp of the first anchoring part 15 and the projection 29 in a radial direction perpendicular to the longitudinal extension of the annular barrier 1. In fig. 12, the expandable metal sleeve 9 also comprises two protrusions 29, between which a circumferential groove 10 is formed, in which circumferential groove 10 the anchor 14 is arranged, and the first anchoring member 15 has a groove 23, in which groove 23 the sealing unit 24a is arranged. The sealing unit 24a comprises a sealing element 25a made of, for example, an elastomer or a polymer, an annular support element 26a on each side of the sealing element 25a, and a key ring shaped element 27a surrounding a portion of the annular support element 26 a. Each anchor 14, 14b may comprise one sealing unit or several sealing units 24a. In fig. 13, the first anchoring part 15 of the anchor 14 has two grooves 23, wherein the spring element 22 is arranged in one groove and the sealing element 25a is arranged in the other groove. During expansion of the expandable metal sleeve 9, the spring element 22 and the sealing element 25a are compressed and after expansion is completed, the spring element 22 and the sealing element 25a will be slightly decompressed due to the small "spring back effect" after expansion of the metal. The spring element 22 and the sealing element 25a will thus always be in contact with the wall portion 5 of the wellbore 4, and when axial loading begins, the spring element 22 and the sealing element 25a will ensure that the first anchor part 15 moves along the inclined outer surface 18 of the second anchor part 16, and thus the first anchor part 15 will be pushed radially outwards, as indicated by the broken line in fig. 3. The spring element 22 and the sealing element 25a may also be arranged on the inner surface 20 of the second anchoring part 16 with two grooves 23.

Fig. 14 shows a perspective view of a portion of another annular barrier. In order to ensure that the first 15 and second 16 anchor parts of the anchor 14 do not slide prematurely relative to each other, the fixation unit 40 is arranged in the circumferential groove 10, i.e. in the groove 23 of the first anchor part 15, such that the first 15 and second 16 anchor parts do not slide relative to each other. The fixing unit 40 comprises an annular member 42 extending all the way around the expandable metal sleeve 9, and each end of the annular member 42 is connected with a frangible element 41. The annular member 42 is a sealing element 25a made of, for example, an elastomer or a polymer, wherein the sealing element 25a is open and each end is connected with the frangible element 41 by a connecting member 40A, 40B. When the expandable metal sleeve 9 expands, the frangible element 41 breaks and the first 15 and second 16 anchor members are then able to slide relative to each other. The first anchor member 15 has a slit 30 to provide a more flexible first anchor member 15. Instead of the frangible element 41, the connecting members 40A, 40B can also be fastened to the first anchor member 15 by means of a pin 41A, the pin 41A breaking during inflation of the expandable metal sleeve 9. In fig. 15, the frangible element 41 is shown in the pin position and is breaking during expansion. The sealing element 25a is connected to the frangible element 41 by at least one connecting part through which the frangible element 41 in the form of a pin extends and further into a hole in the first anchor part 15, thereby forming the fixing unit 40. After the expandable metal sleeve 9 has been expanded and has broken, the first anchoring member 15 is free to slide relative to the second anchoring member 16 when the metal well tubular structure 3 is subjected to an axial load, i.e. when the metal well tubular structure 3 is axially moved relative to the other metal well tubular structure 3 b.

As can be seen in fig. 15, the groove 23 has a first length L along the axial extension L ₁ And the first anchoring member 15 has a second length L along the axial extension direction L ₂ Wherein the first length L ₁ Is a second length L ₂ And preferably is at least 10% of the second length L ₂ At least 20%.

In fig. 16, the first anchoring member 15 comprises two grooves 23. In the first groove 23, a sealing element 25a is arranged around the expandable metal sleeve 9 and the first anchoring member 15. In the second recess 23 of the first anchor part 15, a fixing unit 40 is arranged. The second groove 23 does not have to extend all the way/full-circle around the first anchoring member 15. Both grooves 23 have a trapezoidal cross-sectional shape such that neither the sealing element 25a nor the fixing unit 40 can be moved radially outwards, thereby moving out of the grooves 23. The fixing unit 40 comprises a frangible element 41 in the form of a frangible pin extending into the first anchor member 15.

Instead of having the second anchor 14b as shown in fig. 1 (wherein the second anchor 14b is inclined in the opposite direction to the first anchor 14 with respect to the axial extension direction L), the first anchor 14 and the second anchor 14b are arranged in the same circumferential groove 10 as shown in fig. 17. The sealing elements 25a arranged in each groove 23 of the first anchor part 15 face each other and the second anchor parts 16 face away from each other. In this way, the annular barrier 1 can easily provide anchoring of the metal well tubular structure 3 with respect to another metal well tubular structure 3b and thus take up axial loads, whether the movement is upward or downward. The first anchor 14 and the second anchor 14b are provided with a distance by a protrusion smaller than the protrusion 29 forming the circumferential groove 10.

In fig. 18A, 18B, the expandable metal sleeve 9 is fastened to the tubular metal part 7 of the metal well tubular structure 3 by means of a connection element 51, which connection element 51 is fastened to the tubular metal part 7 by means of a welded connection 52 and welded to both parts of the expandable metal sleeve 9 by means of the welded connection 52. The anchor 14 is arranged opposite the connecting element 51 in a circumferential groove 10 formed by two parts of the expandable metal sleeve 9 and the connecting element 51. During expansion of the expandable metal sleeve 9, the connecting element 51 expands as shown in fig. 18B, pressing the anchor 14 radially outwards, so as to enhance the function of the anchor 14 after the expansion has ended. The connecting element 51 has a groove 53, in which groove 53 the protrusion of the first anchoring member 15 may extend, or the groove 53 will leave room for a weld to provide a proper fastening of the first anchoring member 15 to the connecting element 51. The expandable metal sleeve 9 expands until the sealing unit 24, the first anchoring member 15 and the sealing element 25a abut the inner surface of the further metal well tubular structure 3B, as shown in fig. 18B.

Fig. 1 also discloses a downhole completion system 100 comprising the above annular barrier 1 and a metal well tubular structure 3.

"fluid" or "wellbore fluid" refers to any type of fluid that is present downhole in an oil or gas well, such as natural gas, oil-based mud, crude oil, water, and the like. "gas" refers to any type of gas component present in a well, completion, or open hole, and "oil" refers to any type of oil component, such as crude oil, oil-containing fluids, and the like. The gas, oil and water fluids may thus each comprise other elements or substances than gas, oil and/or water.

"casing" or "metal well tubular structure" refers to any type of pipe, conduit, tubular structure, liner, string, etc. used downhole in connection with the production of oil or gas.

While the invention has been described above in connection with preferred embodiments thereof, several modifications which are conceivable without departing from the invention as defined by the following claims will be apparent to those skilled in the art.

Claims (15)

1. An annular barrier (1) for providing zone isolation downhole in an annulus (2) between a metal well tubular structure (3) and another metal well tubular structure (3 b) or a wall (5) of a borehole (4), the annular barrier comprising:

-a tubular metal part (7) configured to be mountable as part of the metal well tubular structure, the tubular metal part having an outer surface (8), an opening (6) and an axial extension direction (L) along the metal well tubular structure; and

an expandable metal sleeve (9) surrounding the tubular metal part, the first expandable metal sleeve having a circumferential groove (10), a first end (11) and a second end (12), each end of the expandable metal sleeve being connected to an outer surface of the tubular metal part,

wherein the annular barrier further comprises an anchor (14) arranged in the circumferential groove, the anchor comprising a first anchor part (15) and a second anchor part (16), the first anchor part at least partially overlapping the second anchor part in a radial direction perpendicular to the axial extension direction such that an inner surface (17) of the first anchor part at least partially abuts an outer surface (18) of the second anchor part.

2. An annular barrier according to claim 1, wherein the inner surface of the first anchor part and the outer surface of the second anchor part are inclined with respect to the axial extension direction.

3. An annular barrier according to claim 1 or 2, wherein the first and second anchoring members are one piece.

4. An annular barrier according to any of claims 1-3, wherein the first anchoring part is formed as one piece and the second anchoring part is formed as another piece.

5. An annular barrier according to claim 4, wherein the first anchoring member is shaped as a first split ring and the second anchoring member is shaped as a second split ring.

6. An annular barrier according to any of the preceding claims, wherein the first anchoring part further comprises an outer surface (19), the second anchoring part comprises an inner surface (20), the outer surface of the first anchoring part comprises friction enhancing means (21) and faces another metal well tubular structure or a wall part facing the borehole.

7. An annular barrier according to claim 6, wherein the friction enhancing mechanism is a pointed portion (21 a) or a groove (21 b).

8. An annular barrier according to any of claims 5-7, wherein the outer surface of the first anchoring member has at least one groove (23) in which a spring element (22) is arranged.

9. An annular barrier according to claim 6, wherein the friction between the inner surface of the first anchor part and the outer surface of the second anchor part is smaller than the friction between the inner surface of the second anchor part and the circumferential groove.

10. An annular barrier according to any of the preceding claims, wherein the inner surface of the second anchoring member has at least one groove, in which a spring element (22) is arranged.

11. An annular barrier according to any of the preceding claims, wherein the anchor comprises a third anchor part (31) having an outer surface (32) abutting a second inner surface (17 a) of the first anchor part, such that the first anchor part is arranged between the third anchor part and the second anchor part, and the inner surfaces of the third anchor part and the second anchor part face and abut the circumferential groove.

12. An annular barrier according to any of the preceding claims, further comprising a second anchor (14 b) comprising a first anchor part (15 b) and a second anchor part (16 b), the first anchor part at least partly overlapping the second anchor part (16 b) in a radial direction perpendicular to the axial extension direction such that an inner surface (17 b) of the first anchor part at least partly abuts an outer surface (18 b) of the second anchor part, the inner surface of the first anchor part and the outer surface of the second anchor part being inclined with respect to the axial extension direction in a direction opposite to the direction in which the inner surface of the first anchor part and the outer surface of the second anchor part are inclined with respect to the axial extension direction.

13. An annular barrier according to any of the preceding claims, wherein the expandable metal sleeve has a second circumferential groove (10 b) in which a sealing unit (24) is arranged.

14. An annular barrier according to any of the preceding claims, wherein the expandable metal sleeve comprises at least two sealing units, the anchor being arranged between the two sealing units.

15. A downhole completion system (100) comprising a metal well tubular structure (3) and an annular barrier (1) according to any of claims 1-14.