Annular barrier with axial force mechanism

1. An annular barrier to be expanded in an annulus between a well tubular structure and an inside wall of a borehole downhole for providing zone isolation between a first zone and a second zone of the borehole, the annular barrier comprising:

a tubular part extending in a longitudinal direction for mounting as part of the well tubular structure,

an expandable metal sleeve surrounding the tubular part and defining a space being in fluid communication with an inside of the tubular part,

a first fluid passage for letting fluid into the space to expand the sleeve, and

a connection unit comprising:

a connection part slidably connected with the tubular part, a first end of the expandable sleeve being connected with the connection part,

a stationary part fixedly connected with the tubular part, and

an actuation mechanism adapted to induce an axial force on the first end of the expandable sleeve, whereby the connection part is displaced in the longitudinal direction towards a second end of the expandable sleeve connected with the tubular part,

wherein the actuation mechanism further comprises a pressure chamber at least partly defined between a face of the connection part and a face of the stationary part, and a second fluid passage for letting fluid into the pressure chamber to push the connection part in the longitudinal direction, and

wherein the first fluid passage is provided in the connection part, thereby fluidly connecting the space defined by the expandable sleeve and the pressure chamber.

2. An annular barrier according to claim 1 , comprising two connection units, each comprising the connection part connected to a first and a second end of the expandable metal sleeve, respectively.

3. An annular barrier according to claim 1 , wherein said first fluid passage forms a fluid bypass passage for providing fluid communication between the pressure chamber and the space defined by the expandable metal sleeve only when the connection part has been displaced in the longitudinal direction.

4. An annular barrier according to claim 1 , wherein the first fluid passage comprises a plurality of first fluid passages.

5. An annular barrier according to claim 1 , wherein the first fluid passage provided in the connection part is positioned radially outwards of the part of the connection part that is sealed against the tubular part.

6. An annular barrier according to claim 1 , wherein the first end of the metal sleeve is spaced radially outward from the tubular part and the first fluid passage.

7. An annular barrier according to claim 1 , wherein an inner surface of the first end of the metal sleeve is spaced radially outward from the first fluid passage.

8. An annular barrier according to claim 1 , wherein the metal sleeve is expandable from an uninflated state to a permanent, set inflated state upon the application of pressurized fluid to the space.

9. A well system comprising the well tubular structure and the annular barrier according to claim 1 .

10. A method for expanding an annular barrier according to claim 1 , in an annulus between a well tubular structure and an inside wall of a borehole downhole, the method comprising:

at least partly expanding the expandable metal sleeve by letting fluid into the space defined by the expandable metal sleeve,

inducing an axial force on the connection part whereto one end of the expandable metal sleeve is connected, and

expanding the expandable metal sleeve until the sleeve seals against the inside wall of the borehole.