Annular barrier having a downhole expandable tubular

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

a tubular part, the tubular part being a separate tubular part or a casing part for mounting as part of the well tubular structure,

a downhole expandable tubular to be expanded in the annulus downhole from a first outer diameter to a second outer diameter to abut against the inner face of the casing or borehole, the downhole expandable tubular having a first end section, a second end section and an intermediate section extends from the first end section to the second end section, and the downhole expandable tubular surrounding the tubular part, said first and second end sections of the downhole expandable tubular being connected with the tubular part and extending along the axis, and

an annular barrier space between the tubular part and the downhole expandable tubular,

wherein the downhole expandable tubular comprises a one piece construction of metal material, each of the first and second end sections having a higher yield strength than the intermediate section along an entire length of the intermediate section,

wherein the first and second end sections are treated to achieve the higher yield strength to at least partly prevent the first and second end sections from departing from the tubular part, and

wherein the first end section has a length that is substantially equal to a length of the second end section.

2. An annular barrier according to claim 1 , wherein the first and second end sections of the downhole expandable tubular are welded onto the tubular part.

3. An annular barrier according to claim 2 , wherein the higher yield strength is achieved via cold-working.

4. An annular barrier according to claim 1 , wherein the metal material of the end sections has a higher yield strength than the metal material of the intermediate section after metal-working of the end sections or the intermediate section.

5. An annular barrier according to claim 1 , wherein the end sections are cold-worked or the intermediate section is heat-treated, annealed or induction-annealed.

6. An annular barrier according to claim 1 , wherein the yield strength of the metal material of the end sections is at least 25% higher than the yield strength of the material of the intermediate section.

7. An annular barrier according to claim 1 , wherein the yield strength of the metal material of the end sections is at least 350 MPa.

8. An annular barrier according to claim 1 , wherein the end sections and the intermediate section have substantially the same thickness along the longitudinal axis.

9. An annular barrier according to claim 1 , wherein the tubular comprises steel or stainless steel.

10. An annular barrier according to claim 1 , further comprising at least one sealing element surrounding the downhole expandable tubular.

11. An annular barrier according to claim 1 , further comprising an expansion opening in the tubular part through which fluid may enter the space in order to expand the expandable tubular.

12. A downhole completion system comprising:

a well tubular structure, and

the annular barrier according to claim 1 .

13. A manufacturing method for manufacturing a downhole expandable tubular of an annular barrier to be expanded in an annulus between a well tubular structure and an inside face of a casing or borehole downhole for providing zone isolation between a first zone and a second zone of the casing or borehole, the annular barrier extending along a longitudinal axis, the annular barrier comprising:

a tubular part, the tubular part being a separate tubular part or a casing part for mounting as part of the well tubular structure,

the downhole expandable tubular configured to be expanded in the annulus downhole from a first outer diameter to a second outer diameter to abut against the inner face of the casing or borehole, the downhole expandable tubular having a first end section, a second end section and an intermediate section extends from the first end section to the second end section, and the downhole expandable tubular surrounding the tubular part, said first and second end sections of the downhole expandable tubular being connected with the tubular part and extending along the axis, and

an annular barrier space between the tubular part and the downhole expandable tubular,

wherein the downhole expandable tubular comprises a one piece construction of metal material, each of the first and second end sections having a higher yield strength than the intermediate section along an entire length of the intermediate section, and

wherein the first and second end sections are treated to achieve the higher yield strength to at least partly prevent the first and second end sections from departing from the tubular part, the method comprising:

providing a metal tubular blank made of a metal material, and

metal-working the end sections so that the metal material of the end sections has a higher yield strength than the metal material of the intermediate section.

14. A manufacturing method according to claim 13 , wherein the metal-working comprises:

cold-working the intermediate section to a thickness which is smaller than that of the end sections,

heat-treating the intermediate section, and

cold-working the end sections.

15. A manufacturing method according to claim 13 , wherein the metal-working comprises:

cold-working the intermediate section and the end sections, and

heat-treating the intermediate section.

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

a tubular part, the tubular part being a separate tubular part or a casing part for mounting as part of the well tubular structure,

a downhole expandable tubular to be expanded in the annulus downhole from a first outer diameter to a second outer diameter to abut against the inner face of the casing or borehole, the downhole expandable tubular having a first end section, a second end section and an intermediate section extends from the first end section to the second end section, and the downhole expandable tubular surrounding the tubular part, said first and second end sections of the downhole expandable tubular being connected with the tubular part and extending along the axis, and

an annular barrier space between the tubular part and the downhole expandable tubular,

wherein the downhole expandable tubular comprises a one piece construction of metal material, each of the first and second end sections having a higher yield strength than the intermediate section along an entire length of the intermediate section, and

wherein the first and second end sections are treated to achieve the higher yield strength to at least partly prevent the first and second end sections from departing from the tubular part,

wherein the first and second end sections of the downhole expandable tubular are welded onto the tubular part without any connection parts.

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

a tubular part, the tubular part being a separate tubular part or a casing part for mounting as part of the well tubular structure,

a downhole expandable tubular to be expanded in the annulus downhole from a first outer diameter to a second outer diameter to abut against the inner face of the casing or borehole, the downhole expandable tubular having a first end section, a second end section and an intermediate section extends from the first end section to the second end section, and the downhole expandable tubular surrounding the tubular part, said first and second end sections of the downhole expandable tubular being connected with the tubular part and extending along the axis, and

an annular barrier space between the tubular part and the downhole expandable tubular,

wherein the downhole expandable tubular comprises a one piece construction of metal material, each of the first and second end sections having a higher yield strength than the intermediate section along an entire length of the intermediate section, and

wherein the first and second end sections are treated to achieve the higher yield strength to at least partly prevent the first and second end sections from departing from the tubular part,

wherein the intermediate section is dimensioned to seal with the casing or borehole, and the first and second end sections are not dimensioned to seal with the casing or borehole.

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

a tubular part, the tubular part being a separate tubular part or a casing part for mounting as part of the well tubular structure,

a downhole expandable tubular to be expanded in the annulus downhole from a first outer diameter to a second outer diameter to abut against the inner face of the casing or borehole, the downhole expandable tubular having a first end section, a second end section and an intermediate section extends from the first end section to the second end section, and the downhole expandable tubular surrounding the tubular part, said first and second end sections of the downhole expandable tubular being connected with the tubular part and extending along the axis, and

an annular barrier space between the tubular part and the downhole expandable tubular,

wherein the downhole expandable tubular comprises a one piece construction of metal material, each of the first and second end sections having a higher yield strength than the intermediate section along an entire length of the intermediate section, and

wherein the first and second end sections are treated to achieve the higher yield strength to at least partly prevent the first and second end sections from departing from the tubular part,

wherein the intermediate section alone defines a sealing/engagement section and the first and second end sections are positioned outside of the sealing/engagement section.