Claims
1. An annular barrier (10) to be expanded in an annulus (2) between a well
tubular structure (1) and a wall (5) of a borehole (6) downhole for providing zone
isolation between a first zone (101) having a first pressure (Pi) and a second
zone (102), the annular barrier comprising:
- a tubular metal part (7) for mounting as part of the well tubular structure, the tubular metal part having a first expansion opening (3), an axial extension (L) and an outer face (4),
- an expandable sleeve (8) surrounding the tubular metal part and having an inner face (9) facing the tubular metal part and an outer face (16) facing the wall of the borehole, each end (12), (13) of the expandable sleeve being connected with the tubular metal part, and
- an annular space (15) between the inner face of the expandable sleeve and the tubular metal part, the annular space having a space pressure (Ps),
wherein fluid inside the tubular metal part has a tubular pressure (Pt), and wherein the annular barrier comprises an expansion unit (11) having a first inlet (17) in fluid communication with the expansion opening (3), a second inlet (18) in fluid communication with the first zone (101) and an outlet (19) in fluid communication with the annular space, and the expansion unit comprising an element (20) movable at least between a first position and a second position, in the first position the expansion opening (3) being in fluid communication with the outlet (19) and the tubular pressure (Pt) being higher than the first pressure (Pi), and in the second position the outlet (19) being in fluid communication with the first zone (101) and the first pressure (Pi) being higher than the tubular pressure (Pt), wherein the tubular metal part (7) comprises at least one second expansion opening (3a) being fluidly connected with the first inlet.
2. An annular barrier according to claim 1, wherein the expansion unit comprises a collection part (21) fluidly connected to the first expansion opening and the second expansion opening.
3. An annular barrier according to claim 2, wherein the collection part comprises a collection sleeve (22) arranged outside the tubular metal part and connected to the tubular metal part, forming an annular chamber (23) between the tubular metal part and the collection sleeve.

4. An annular barrier according to claim 3, wherein the first expansion opening and the second expansion opening are fluidly connected to the annular chamber, and the first inlet is fluidly connected to the annular chamber.
5. An annular barrier according to claim 4, wherein one or more groove(s) (25, 26) are arranged in the collection sleeve and/or the tubular metal part facing the annular chamber.
6. An annular barrier according to claim 4 or 5, wherein the collection sleeve has an outer sleeve face (24) in which one or more circumferential groove(s) (25) is/are arranged.
7. An annular barrier according to claim 6, wherein the outer sleeve face has one or more longitudinal groove(s) (26) along the axial extension.
8. An annular barrier according to claim 7, wherein the one or more longitudinal groove(s) is/are in fluid communication with the second inlet.
9. An annular barrier according to any of claims 4-8, wherein a filtering element (27), such as a slotted or perforated plate, is arranged between the tubular metal part and the collection sleeve and configured to filtrate the fluid from inside the tubular metal part.
10. An annular barrier according to any of claims 1-9, wherein the expansion unit comprises a shuttle valve (lib) and the element of the expansion unit is comprised in the shuttle valve.
11. An annular barrier according to claim 10, wherein the element of the expansion unit moves in the axial extension or radially perpendicular to the axial extension.
12. An annular barrier (10) to be expanded in an annulus (2) between a well tubular structure (1) and a wall (5) of a borehole (6) downhole for providing zone isolation between a first zone (101) having a first pressure (Pi) and a second zone (102), the annular barrier comprising:

- a tubular metal part (7) for mounting as part of the well tubular structure, the tubular metal part having a first expansion opening (3), an axial extension (L) and an outer face (4),
- an expandable sleeve (8) surrounding the tubular metal part and having an inner face (9) facing the tubular metal part and an outer face (16) facing the wall of the borehole, each end (12), (13) of the expandable sleeve being connected with the tubular metal part, and
- an annular space (15) between the inner face of the expandable sleeve and the tubular metal part, the annular space having a space pressure (Ps),
wherein fluid inside the tubular metal part has a tubular pressure (Pt), and wherein the annular barrier comprises an expansion unit (11) having a first inlet (17) in fluid communication with the expansion opening, a second inlet (18) in fluid communication with the first zone and an outlet (19) in fluid communication with the annular space, and the expansion unit comprising an_element (20) movable at least between a first position and a second position, in the first position the expansion opening being in fluid communication with the outlet and the tubular pressure being higher than the first pressure, and in the second position the outlet being in fluid communication with the first zone and the first pressure being higher than the tubular pressure, wherein the expandable sleeve has an expandable sleeve opening (31) opposite the expansion opening, the expansion unit being arranged both in the expansion opening and the expandable sleeve opening so that the outlet is arranged in the annular space.
13. An annular barrier according to any of the claims 1-12, wherein the element is a ball (20b) movable between a first seat (48) when the element is in the first position and a second seat (49) when the element is in the second position.
14. A downhole system (100) comprising:

- a well tubular structure (1), and
- a first annular barrier (10) according to any of the preceding claims.
15. A downhole system (100) according to claim 14, further comprising a
second annular barrier (10b) which, when expanded, isolates a production zone
(102) together with the first annular barrier, the expansion units of the first
annular barrier and the second annular barrier being arranged in a zone (101,)
other than the production zone.