Annular barrier for small diameter wells

1. An annular barrier for being mounted as part of a well tubular metal structure for providing zonal isolation in a small diameter borehole downhole for isolating a first zone from a second zone, the annular barrier having an inner face and comprising:

an expandable metal sleeve having a first end and a second end, an inner face and an outer face facing the borehole, the expandable metal sleeve being expandable by direct exposure to pressurized fluid between an unexpanded position radially spaced away from the borehole and an expanded position in contact with the borehole,

a first end part having a first end connected to the first end of the expandable metal sleeve and a second end for being mounted as part of the well tubular structure, the first end part having an inner face and

a second end part having a first end connected to the second end of the expandable metal sleeve and a second end for being mounted as part of the well tubular structure, the second end part having an inner face,

wherein an outer diameter of the first and second end parts is equal to or greater than an outer diameter of the expandable metal sleeve in the unexpanded position, and the outer diameter of a metal portion of the expandable metal sleeve in the expanded position is greater than the outer diameter of the first and second parts and an outer diameter of the well tubular structure,

wherein the first end of the first end part is connected end to end to the first end of the expandable metal sleeve, and the first end of the second end part is connected end to end to the second end of the expandable metal sleeve, the expandable metal sleeve and the first and second end parts are connected so that the inner face of the expandable metal sleeve and the inner faces of the first and second end parts constitute the inner face of the annular barrier, and

wherein the second ends of the end parts are provided with male or female thread connections for being mounted to corresponding male or female thread connections of the well tubular metal structure.

2. An annular barrier according to claim 1 , wherein the second end of the first end part is provided with a female thread connection and the second end of the second end part is provided with a male thread connection.

3. An annular barrier according to claim 1 , wherein the first and second end parts are connected to the first and second ends of the expandable metal sleeve by means of a standard connection.

4. An annular barrier according to claim 1 , wherein sealing elements are arranged on the outer face of the expandable metal sleeve.

5. An annular barrier according to claim 4 , further comprising a split ring-shaped retaining element, the split ring-shaped retaining element forming a back-up for the sealing element.

6. An annular barrier according to claim 1 , wherein the expandable metal sleeve has:

a first section having a first outer diameter and a first thickness, and

at least two circumferential projections having a thickness which is larger than the first thickness and having a second outer diameter which is larger than the first outer diameter, so that when expanding the expandable metal sleeve, the first section bulges more radially outwards than the circumferential projections, resulting in the expandable metal sleeve being strengthened.

7. An annular barrier according to claim 1 , wherein the expandable metal sleeve is made of a material which is more pliant than the material of the first and second end parts.

8. An annular barrier according to claim 1 , wherein the first and second end parts are tubular and have a maximum wall thickness which is larger than a maximum wall thickness of the expandable metal sleeve.

9. An annular barrier according to claim 1 , wherein the expandable metal sleeve has a length, and no tubular is arranged within the expandable metal sleeve along the entire length of the expandable metal sleeve.

10. A well tubular metal structure having a plurality of tubular sections and at least one annular barrier according to claim 1 ; wherein the first and second end parts and the expandable metal sleeve are mounted in succession with the plurality of tubular sections, so that the first end part and the second end part are arranged between the expandable metal sleeve and the tubular sections along an axial extension of the well tubular metal structure.

11. A well tubular metal structure according to claim 10 , wherein the well tubular metal structure has an inner face, and the expandable metal sleeve and the first and second end parts are connected so that the inner face of the expandable metal sleeve and the inner faces of the first and second end parts constitute the inner face of the annular barrier and the inner face of the well tubular metal structure.

12. A well tubular metal structure according to claim 10 , wherein a second annular barrier according to claim 1 is mounted as part of the well tubular metal structure and a plurality of tubular sections is mounted between the annular barriers.

13. A well tubular metal structure according to claim 10 , wherein the first end part creates a first distance between the expandable metal sleeve and one of the plurality of tubular sections, and the second end part creates a second distance between the expandable metal sleeve and another one of the plurality of tubular sections.

14. A completion method of preparing an annular barrier according to claim 1 before being mounted as part of the well tubular metal structure, said completion method comprising:

providing the expandable metal sleeve,

making the female thread connection in the first end part,

making the male thread connection in the second end part, and

mounting the first and second end part with the expandable metal sleeve.

15. A completion method comprising:

mounting the annular barrier according to claim 1 as part of the well tubular metal structure,

submerging the well tubular metal structure into the borehole,

retracting the well tubular metal structure in the event that the well tubular metal structure cannot be submerged to a predetermined depth,

dismounting the annular barrier and part of a plurality of tubular sections of the well tubular metal structure,

replacing the first and second end parts with other first and second end parts having a smaller outer thread diameter compared to the first and second end parts,

replacing part of the plurality of tubular sections with other tubular sections having a smaller outer diameter,

remounting the annular barrier having the other first and second end parts of a smaller outer thread diameter, and

submerging the remounted well tubular metal structure.

16. An annular barrier according to claim 1 , wherein the first end of each of the first part and the second part is detachably connected to the expandable metal sleeve.

17. An annular barrier according to claim 16 , wherein each of the first and second end of the expandable metal sleeve includes a flat end surface, and the first end of each of the first and second parts include an interior flat surface axially displaced from a respective end of the first and second parts, wherein each said flat end surface abuts the respective interior flat surface of the first and second parts when the first and second parts are connected to the expandable metal sleeve.

18. An annular barrier according to claim 17 , wherein each of the first and second parts includes an overlapping portion that overlaps the outer face of the first and second ends of the expandable metal sleeve, each said overlapping portion extending in an axial direction relative to the respective interior flat surface of the first and second parts.

19. An annular barrier according to claim 17 , wherein the flat end surfaces and the interior flat surfaces extend substantially perpendicular to the axial direction.

20. An annular barrier according to claim 16 , wherein the expandable metal sleeve comprises a material that is more pliant than a material of each of the first part and the second part, and each of the first part and the second part has a thickness that is greater than a thickness of the expandable metal sleeve.