Annular barrier with pressure amplification

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

a tubular part for mounting as part of the well tubular structure and having an expansion opening,

an expandable sleeve surrounding the tubular part, each end of the expandable sleeve being connected with the tubular part, and

an annular barrier space between the tubular part and the expandable sleeve,

wherein the annular barrier further comprises a pressure intensifying assembly having an inlet in a first end in fluid communication with the expansion opening and having an outlet in a second end in fluid communication with the annular barrier space, and wherein the pressure intensifying assembly comprises a piston having a first end and a second end, the piston being slidably arranged within a piston housing, the piston housing comprising a first cylinder having a first inner diameter corresponding to an outer diameter of the first end of the piston and having a first end surface area, and a second cylinder having a second diameter corresponding to an outer diameter of the second end of the piston and having a second end surface area, the first end surface area being larger than the second end surface area,

wherein the pressure intensifying assembly further comprises a feed fluid connection configured to be in fluid communication with the inlet and the expansion opening for allowing fluid to enter the second cylinder, and wherein the pressure intensifying assembly further comprises a first one-way check valve arranged in the feed fluid connection for preventing fluid from exiting the second cylinder during compression of fluid by the piston and for allowing fluid to enter the second cylinder during decompression of fluid by the piston,

wherein the pressure within the annular barrier space is increased by the pressure intensifying assembly to expand the expandable sleeve, whereby pressure in the annular space is greater than a pressure inside the tubular part adjacent the annular barrier, and

wherein each end of the expandable sleeve is connected to the tubular part by a respective connecting part, and wherein the pressure intensifying assembly is disposed at least partly within one of the respective connecting parts.

2. An annular barrier according to claim 1 , wherein the pressure intensifying assembly further comprises a second one-way check valve arranged between the feed fluid connection and the outlet of the pressure intensifying assembly for preventing pressurised fluid from entering the second cylinder during decompression of fluid by the piston and for allowing pressurised fluid to exit the pressure intensifying assembly through the outlet during compression of fluid by the piston.

3. An annular barrier according to claim 1 , wherein the pressure intensifying assembly comprises a plurality of pressure intensifying assemblies.

4. An annular barrier according to claim 3 , wherein the outlet of the pressure intensifying assembly comprises a pressure collecting chamber in fluid communication with a plurality of second ends of a plurality of pistons and in fluid communication with the annular barrier space.

5. An annular barrier according to claim 1 , wherein an excess fluid connection between the pressure intensifying assembly and the borehole allows fluid to flow from the pressure intensifying assembly into the borehole.

6. An annular barrier according to claim 1 , wherein the pressure intensifying assembly comprises a void within the piston housing between the first end and the second end of the piston.

7. An annular barrier according to claim 1 , further comprising a one-way valve arranged in fluid communication with the borehole and the annular barrier space, allowing fluid flow from the borehole into the annular barrier space.

8. An annular barrier according to claim 1 , wherein the annular barrier comprises a first and a second pressure intensifying assemblies arranged in series, the first pressure intensifying assembly comprising a first inlet and a first outlet and the first inlet being in fluid communication with the expansion opening, the second pressure intensifying assembly comprising a second inlet and a second outlet and the second outlet being in fluid communication with the annular barrier space.

9. An annular barrier according to claim 1 , wherein the annular barrier comprises a first and a second pressure intensifying assemblies and at least one intermediate pressure intensifying assembly arranged in series, the first pressure intensifying assembly comprising a first inlet and a first outlet and the first inlet being in fluid communication with the expansion opening, the second pressure intensifying assembly comprising a second inlet and a second outlet and the second outlet being in fluid communication with the annular barrier space, and wherein the at least one intermediate pressure intensifying assembly comprises an intermediate inlet in fluid communication with the first outlet and an intermediate outlet being in fluid connection with second inlet.

10. An annular barrier according to claim 1 , wherein the pressure intensifying assembly comprises a hydraulic pressure intensifier or a hydraulic pressure intensifier with a double-acting piston.

11. An annular barrier according to claim 1 , wherein a second pressure intensifying assembly is arranged in an end of the annular barrier opposite to the pressure intensifying assembly.

12. Annular barrier system comprising:

a well tubular structure, and

at least an annular barrier according to claim 1 arranged as part of the well tubular structure.

13. A method of placing the annular barrier according to claim 1 in the annulus, comprising the steps of:

connecting the annular barrier with the well tubular structure,

placing the unexpanded annular barrier in a desired position downhole,

pressurising a fluid within the tubular part,

intensifying the pressure only in the annular barrier space by the pressure intensifying assembly, and

expanding the expandable sleeve.

14. A method of using annular barriers according to claim 1 in an annulus to seal off an inflow control section, comprising the steps of:

connecting two annular barriers with the well tubular structure and in between them the inflow control section,

placing the two annular barriers and the inflow control section in a desired position downhole,

pressurising the tubular part and expanding the annular barriers by intensifying the pressure only in the annular barriers for providing zone isolation between a first zone and a second zone of the borehole, the first zone having a first fluid pressure and the second zone having a second fluid pressure,

stopping the pressurising of the tubular part, and

activating the inflow control section for starting a production of fluid into the well tubular structure.