Annular barrier

1. An annular barrier configured to be arranged on an outer face of a well tubular metal structure for providing zonal isolation in an annulus downhole, comprising:

an annular space defined by a first expandable metal sleeve part and a second expandable metal sleeve part, the first expandable metal sleeve part having an outer face configured to face away from the outer face of the well tubular metal structure and the second expandable metal sleeve part having an outer face configured to face the outer face of the well tubular metal structure when arranged around the well tubular metal structure,

wherein at least part of the second expandable metal sleeve part is hydraulically expandable from a non-expanded position to an expanded position that is radially inwards compared to the non-expanded position, by introducing hydraulic fluid into the annular space when the annular barrier is mounted on the well tubular metal structure, and

wherein the annular barrier further comprises a first inner annular sealing element arranged on the outer face of the second expandable metal sleeve part configured to seal between the second expandable metal sleeve part and the well tubular metal structure.

2. The annular barrier according to claim 1 , further comprising a second inner annular sealing element arranged on the outer face of the second expandable metal sleeve part configured to seal between the second expandable metal sleeve part and the well tubular metal structure.

3. The annular barrier according to claim 2 , wherein the first inner annular sealing element is arranged at a distance from the second inner annular sealing element, and the second expandable metal sleeve part has an opening between the first inner annular sealing element and the second inner annular sealing element.

4. The annular barrier according to claim 3 , wherein a burstable element, such as a burst disc, is arranged in the opening.

5. The annular barrier according to claim 1 , wherein the first expandable metal sleeve part and the second expandable metal sleeve part are made in one piece.

6. The annular barrier according to claim 1 , wherein the first expandable metal sleeve part and the second expandable metal sleeve part are two sleeves welded together enclosing the annular space.

7. The annular barrier according to claim 1 , wherein the second expandable metal sleeve part has a smaller thickness than that of the first expandable metal sleeve part.

8. The annular barrier according to claim 1 , wherein the second expandable metal sleeve part is made of a material having a higher ductility than that of the first expandable metal sleeve part.

9. The annular barrier according to claim 1 , wherein each of the first expandable metal sleeve part and the second expandable metal sleeve part has a first end part, an intermediate part and a second end part, and the end parts have a higher thickness than that of the intermediate parts.

10. The annular barrier according to claim 1 , further comprising a port for energising the inner annular sealing elements when mounting the annular barrier on the well tubular metal structure.

11. The annular barrier according to claim 10 , wherein the port is in fluid communication with the annular space.

12. The annular barrier according to claim 1 , further comprising at least one outer annular sealing element arranged on the outer face of the first expandable metal sleeve part.

13. The annular barrier according to claim 1 , wherein the expandable metal sleeve parts have at least two projections on the outer face forming a groove in which the annular sealing element is arranged.

14. A downhole system comprising:

a well tubular metal structure having an aperture, and

at least one annular barrier according to claim 1 ,

wherein the at least one annular barrier is arranged so that the aperture is arranged between the first inner sealing element and the second inner sealing element.

15. A method of arranging an annular barrier according to claim 1 on the outer face of the well tubular metal structure mounted from tubing parts or a joint for providing zonal isolation in an annulus downhole, comprising:

sliding the annular barrier onto and along one of the tubing parts or joints of the well tubular metal structure,

activating the inner annular sealing element(s) by pressurising the annular space so that the second expandable metal sleeve part presses against the outer face of the well tubular metal structure,

mounting the tubing part having the annular barrier as part of the well tubular metal structure,

inserting the well tubular metal structure into a borehole providing the annulus around the well tubular metal structure,

expanding the annular barrier by expanding at least the first expandable metal sleeve part into abutment against a wall of the borehole or another well tubular metal structure isolating one part of the annulus from another part.

16. The annular barrier according to claim 1 , wherein:

in the non-expanded position, the at least part of the second expandable metal sleeve part is configured to be spaced a first distance away from the well tubular metal structure, and

in the expanded position, the at least part of the second expandable metal sleeve part is configured to be expanded to a second distance away from the well tubular metal structure, the second distance being less than the first distance.