Downhole expandable metal tubular

1. A downhole expandable metal tubular having an axial extension, to be expanded in a well downhole to abut an inner face of a casing or a borehole, comprising:

a first section of a metal material having a first outer diameter,

two circumferential projections of said metal material having a second outer diameter which is larger than the first outer diameter, and

a second section of said metal material arranged between the two projections, each projection having an inclined face tapering from the second outer diameter towards the second section,

wherein the first section, the projections and the second section form a one piece construction of said metal material, and

wherein the second section has a third outer diameter which is smaller than the first outer diameter in an unexpanded condition, and a sealing element is arranged between the projections opposite the second section so that during expansion, the second section bulges more radially outwards than the first section, forcing the sealing element radially outwards in an expanded condition.

2. A downhole expandable metal tubular according to claim 1 , wherein the expandable metal tubular has an inner diameter which is the same along the axial extension in the unexpanded condition.

3. A downhole expandable metal tubular according to claim 1 , wherein the first section has a first thickness and the second section has a second thickness, the second thickness being at least 25% smaller than the first thickness.

4. A downhole expandable metal tubular according to claim 1 , wherein the inclined face of the projections forms an angle in relation to the axial extension, said angle being at least 110°, when the second section is in the expanded condition.

5. A downhole expandable metal tubular according to claim 1 , wherein the sealing element is arranged in the second section, the second section including the sealing element has an outer diameter which is substantially the same as the second outer diameter of the projections.

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

a tubular part adapted to be mounted as part of the well tubular structure,

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

an annular space between the downhole expandable metal tubular and the tubular part.

7. A downhole completion comprising:

a well tubular structure, and

a downhole expandable metal tubular according to claim 1 .

8. A downhole completion comprising:

the well tubular structure, and

an annular barrier according to claim 6 ,

wherein the tubular part of the annular barrier is mounted as part of the well tubular structure.

9. A sealing expansion method comprising:

arranging a downhole expandable metal tubular according to claim 1 opposite an area to be sealed off, and

expanding the downhole expandable metal tubular to abut the area and thereby sealing off the area.

10. A sealing expansion method comprising:

arranging a downhole completion according to claim 8 , and

expanding the downhole expandable metal tubular of the annular barrier to abut a casing or a borehole in order to provide zone isolation between a first zone and a second zone of the casing or the borehole.