Annular barrier with a valve system

1. An annular barrier for providing zonal isolation in an annulus in a well downhole between a well tubular metal structure and another well tubular metal structure or a wall of a borehole, comprising:

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

an expandable metal sleeve connected with and surrounding the tubular metal part forming an annular space therebetween, the expandable metal sleeve is configured to be expanded in the well downhole from a first outer diameter to a second outer diameter to abut against the well tubular metal structure or the wall of the borehole, and

an expansion opening in the tubular metal part,

wherein the annular barrier further comprises a valve system comprising:

an isolation valve having a first position and a second position, comprising:

an isolation bore,

an isolation piston arranged in the isolation bore dividing the bore into a first bore part and a second bore part in the first position, the isolation piston is maintained in the first position by a shear element configured to break at a predetermined pressure difference between the first bore part and the second bore part,

a first aperture arranged in the first bore part and being in fluid communication with the annular space,

a second aperture arranged in the first bore part and being in fluid communication with the expansion opening through a first fluid channel,

a third aperture arranged in the second bore part and being in fluid communication with the expansion opening through a second fluid channel,

wherein in the first position the first aperture is in fluid communication with the second aperture, and in the second position the isolation piston prevents fluid communication between the first aperture and the second aperture.

2. The annular barrier according to claim 1 , wherein the first fluid channel comprises a flow restriction.

3. The annular barrier according to claim 1 , wherein the isolation piston has a first piston end facing the first bore part and a second piston end facing the second bore part, the first piston end having a projected area being of substantially the same size as a projected area of the second piston end.

4. The annular barrier according to claim 1 , wherein the first fluid channel provides the flow restriction by having a decrease in a cross-sectional flow area of the first fluid channel.

5. The annular barrier according to claim 1 , wherein the first fluid channel provides the flow restriction by comprising a bend so that the first fluid channel forms an angle of less than 90°.

6. The annular barrier according to claim 1 , wherein the isolation valve comprises a fourth aperture which is in fluid communication with the annulus.

7. The annular barrier according to claim 1 , wherein the valve system further comprises a diverter unit in fluid communication with the expansion opening, the diverter unit dividing fluid from the expansion opening to the first fluid channel and the second fluid channel.

8. The annular barrier according to claim 7 , wherein the diverter unit comprises a unit chamber receiving fluid from the expansion opening and is in fluid communication with the first fluid channel and the second fluid channel.

9. The annular barrier according to claim 8 , wherein the first fluid channel provides the flow restriction by having a cross-sectional flow area smaller than a cross-sectional flow area of the unit chamber.

10. The annular barrier according to claim 9 , wherein the valve piston comprises a piston fluid channel being a through bore providing fluid communication between the first and second bore parts.

11. The annular barrier according to claim 9 , wherein the annular barrier comprises a third opening which is in fluid communication with the annulus.

12. The annular barrier according to claim 1 , wherein the valve system further comprises a closing valve comprising:

a first opening in fluid communication with the expansion opening,

a second opening in fluid communication with the annular space, and

a valve bore having a bore extension and comprising a first bore part having a first inner diameter and a second bore part having a second inner diameter which is larger than that of the first bore part,

wherein the first opening and the second opening are arranged in the first bore part and displaced along the bore extension, the closing valve further comprising:

a valve piston arranged in the bore, the valve piston comprising a first piston part having an outer diameter substantially corresponding to the inner diameter of the first bore part and comprising a second piston part having an outer diameter substantially corresponding to the inner diameter of the second bore part, and

a rupture element preventing movement of the valve piston until a predetermined pressure in the valve bore is reached.

13. The annular barrier according to claim 12 , wherein the closing valve further comprising a locking element adapted to mechanically lock the valve piston when the valve piston is in the closed position, blocking the first opening.

14. The annular barrier according to claim 1 , wherein the annular barrier when expanded divides the annulus into a first zone and a second zone, said annular barrier further comprises an anti-collapsing unit, the anti-collapsing unit having a first inlet which is in fluid communication with the first zone and a second inlet which is in fluid communication with the second zone, and the anti-collapsing unit having an outlet which is in fluid communication with the annular space, and in a first position, the first inlet is in fluid communication with the outlet, equalising the first pressure of the first zone with a space pressure of the annular space, and in a second position, the second inlet is in fluid communication with the outlet, equalising the second pressure of the second zone with the space pressure.

15. Downhole system comprising the annular barrier according to claim 1 and the well tubular metal structure.