Downhole expandable tubular

1. A downhole expandable tubular to be expanded in a well downhole from a first outer diameter (D 1 ) to a second outer diameter (D 2 ) to abut against an inner face of a casing or borehole, the downhole expandable tubular having an outer face and a longitudinal extension (l) and comprising:

at least one first circumferential edge and at least one second circumferential edge provided on the outer face and spaced apart in the longitudinal extension,

wherein a sealing element and a split ring-shaped retaining element are arranged between the first and second circumferential edges, the split ring-shaped retaining element forming a back-up for the sealing element,

wherein the split ring-shaped retaining element has more than one winding, so that when the expandable tubular is expanded from the first outer diameter (D 1 ) to the second outer diameter (D 2 ), the split ring-shaped retaining element expands with the expandable tubular and partly unwinds,

a groove, the groove extending radially inward from the outer face of the tubular, wherein the split ring-shaped retaining element and the sealing element are both located within the groove, and the groove has a fixed width, the groove including an inner surface, a first groove wall that extends radially outward from the inner surface and a second groove wall that extends radially outward from the inner surface,

wherein the split ring-shaped retaining element maintains contact with the first groove wall when the expandable tubular is expanded from the first outer diameter (D 1 ) to the second outer diameter (D 2 ), and

wherein the split ring-shaped retaining element provides a longitudinal force parallel to the longitudinal extension to the sealing element to maintain a longitudinal position of the sealing element within the groove.

2. A downhole expandable tubular according to claim 1 , wherein the split ring-shaped retaining element is arranged in an abutting manner to the sealing element.

3. A downhole expandable tubular according to claim 1 , wherein the split ring-shaped retaining element unwinds by less than one winding when the expandable tubular is expanded from the first outer diameter (D 1 ) to the second outer diameter (D 2 ).

4. A downhole expandable tubular according to claim 1 , wherein the split ring-shaped retaining element has more than one winding in the second outer diameter (D 2 ) of the downhole expandable tubular.

5. A downhole expandable tubular according to claim 1 , wherein the split ring-shaped retaining element has a plurality of windings.

6. A downhole expandable tubular according to claim 1 , wherein the downhole expandable tubular has a first thickness (T 1 ) between the first and second circumferential edges and a second thickness (T 2 ) in adjacent areas, the first thickness (T 1 ) being smaller than the second thickness (T 2 ).

7. A downhole expandable tubular according to claim 1 , wherein the split ring-shaped retaining element and the sealing element substantially fill a gap provided between the first and second circumferential edges.

8. A downhole expandable tubular according to claim 1 , wherein the split ring-shaped retaining element is made of a spring material.

9. A downhole expandable tubular according to claim 1 , wherein the split ring-shaped retaining element is arranged on a first side of the sealing element, and a second split ring-shaped retaining element is arranged on another side of the sealing element opposite the first side.

10. A downhole expandable tubular according to claim 1 , wherein the split ring-shaped retaining element retains the sealing element in a position along the longitudinal extension of the downhole expandable tubular while expanding the split ring-shaped retaining element and the sealing element.

11. A downhole expandable tubular according to claim 1 , wherein the ring-shaped retaining element is a split ring.

12. A downhole expandable tubular according to claim 1 , wherein the first and second circumferential edges are part of the groove.

13. A downhole expandable tubular according to claim 1 , wherein the first and second circumferential edges are extending in a radial extension in relation to the downhole expandable tubular, said radial extension being perpendicular to the longitudinal extension (l) of the downhole expandable tubular.

14. A downhole expandable tubular according to claim 1 , wherein an intermediate element is arranged between the split ring-shaped retaining element and the sealing element.

15. A downhole expandable tubular according to claim 14 , wherein the split ring-shaped retaining element and the intermediate element are arranged in an abutting manner to the sealing element, so that at least one of the split ring-shaped retaining element and the intermediate element abuts the sealing element.

16. A downhole expandable tubular according to claim 1 , wherein the downhole expandable tubular is a patch to be expanded within a casing or well tubular structure in a well, a liner hanger to be at least partly expanded within a casing or well tubular structure in a well, or a casing to be at least partly expanded within another casing.

17. An annular barrier to be expanded in an annulus between a well tubular structure and an inside wall of a borehole or a casing downhole for providing zone isolation between a first zone and a second zone of the borehole, comprising:

a tubular part for mounting as part of the well tubular structure,

a downhole expandable tubular according to claim 1 , surrounding the tubular part and having an outer face facing towards the inside wall of the borehole or the casing, each end of the downhole expandable tubular being connected with the tubular part,

a space between the downhole expandable tubular and the tubular part, and

an expansion opening in the tubular part through which fluid may enter into the space in order to expand the downhole expandable tubular.

18. An annular barrier according to claim 17 , wherein a sleeve is arranged in between the downhole expandable tubular and the tubular part, the sleeve being connected with the tubular part and the downhole expandable tubular, thus dividing the space into a first space section and a second space section.

19. A downhole completion comprising a downhole expandable tubular according to claim 1 , and a casing having an inner face against which at least part of the downhole expandable tubular is expanded.

20. A downhole completion comprising a well tubular structure and an annular barrier according to claim 17 , where the tubular part of the annular barrier is mounted as part of the well tubular structure.

21. A downhole expandable tubular according to claim 1 , wherein the sealing element has a distal end and a proximal end, the proximal end located adjacent the outer face of the downhole expandable tubular and the distal end being spaced from the outer face of the downhole expandable tubular, wherein the split ring-shaped retaining element supports the proximal end of the sealing element and allows the distal end to deform.

22. A downhole expandable tubular according to claim 21 , wherein the distal end is a free end.

23. A downhole expandable tubular according to claim 1 , wherein the first edge and the second edge are integral with the outer face of the tubular.

24. A downhole expandable tubular according to claim 1 , wherein the split ring-shaped retaining element applies force along the longitudinal extension of the tubular.