Completion method and completion system

1. A completion method for completing a well having a top, comprising:

drilling a borehole below a first well tubular metal structure in the well,

circulating mud at least partly while drilling the borehole,

providing a second well tubular metal structure having at least one unexpanded annular barrier having a tubular part surrounded by an expandable metal sleeve, expandable by means of pressurised fluid from within the second well tubular metal structure through a valve assembly into an annular space between the tubular part and the expandable metal sleeve, the valve assembly including a breakable element being exposed to the pressurized fluid via a first opening in the second well tubular metal structure, the second well tubular metal structure having a first end closest to the top and a second end, the valve assembly having a first condition in which fluid communication between an inside of the second well tubular metal structure and the space is disconnected, and having a second condition allowing fluid communication between the inside of the second well tubular metal structure and the annular space,

running the second well tubular metal structure into the well to a position at least partly below the first well tubular metal structure,

circulating cleaning fluid at a first pressure out through the second end to remove at least part of the mud,

displacing cement at a second pressure down through the second well tubular metal structure and out through the second end into an annulus between the second well tubular metal structure and a wall of the borehole,

pressurising the inside of the second well tubular metal structure to a third pressure above the first pressure and the second pressure thus introducing the pressurized fluid into the first opening at the third pressure and breaking the breakable element in the valve assembly, which causes the valve assembly to change from the first condition to the second condition, and

further pressurising the inside of the second well tubular metal structure, expanding the expandable metal sleeve to abut the wall of the borehole.

2. The completion method according to claim 1 , wherein the valve assembly comprises a first piston movable in a first bore from the first condition to the second condition, the first piston being maintained in the first condition by means of the breakable element.

3. The completion method according to claim 2 , further comprising running of the second well tubular metal structure being performed by connecting a drill pipe to the first end of the second well tubular metal structure.

4. The completion method according to claim 3 , further comprising disconnecting the drill pipe subsequent to expanding the expandable metal sleeve.

5. The completion method according to claim 2 , further comprising introducing displacement fluid on top of the cement or the wiper plug to displace the cement.

6. The completion method according to claim 2 , further comprising running a production tubing into the well to a position partly overlapping or above the second well tubular metal structure.

7. The completion method according to claim 2 , wherein while running the second well tubular metal structure the annular space is vented to the annulus.

8. The completion method according to claim 1 , wherein displacing cement is performed by displacing a wiper plug.

9. The completion system according to claim 1 , wherein the valve assembly includes a valve that is positioned to receive the pressurized fluid via the first opening and controls whether the pressurized fluid is permitted to enter the annular space, the valve being connected to the breakable element.

10. The completion system according to claim 9 , wherein the valve is not a check valve.

11. The completion system according to claim 9 , wherein the first opening is in a side wall of the second well tubular metal structure, the first opening running substantially transverse to a longitudinal axis of the second well tubular metal structure.

12. A completion system for completing a well having a top, comprising:

a borehole,

a first well tubular metal structure,

a second well tubular metal structure comprising at least one annular barrier having a tubular part mounted as part of the second well tubular metal structure and surrounded by an expandable metal sleeve, expandable by means of pressurised fluid from within the second well tubular metal structure through a valve assembly into an annular space between the tubular part and the expandable metal sleeve, the valve assembly including a breakable element therein being exposed to the pressurized fluid via a first opening in the second well tubular metal structure, the second well tubular metal structure having a first end closest to the top and a second end, the valve assembly having a first condition in which fluid communication between an inside of the second well tubular metal structure and the annular space is disconnected, and having a second condition allowing fluid communication between the inside of the second well tubular metal structure and the annular space,

a first delivering means for delivering cleanout fluid at a first pressure through the second well tubular metal structure, and

a second delivering means for delivering cement at a second pressure through the second well tubular metal structure,

wherein the breakable element is exposed to the pressurized fluid via the first opening and is breakable at a third pressure being higher than that of the first pressure and of the second pressure, enabling the valve assembly to change from the first condition to the second condition.

13. The completion system according to claim 12 , wherein the first condition is a first position and the second condition is a second position, and the valve assembly comprises a first piston moving in a first bore between the first position and the second position, the first piston being maintained in the first position by means of the breakable element, and the first bore having a first opening in fluid communication with an inside of the second well tubular metal structure, and a second opening in fluid communication with the annular space.

14. The completion system according to claim 13 , wherein the first bore has a third opening in fluid communication with the annulus for venting of pressure in the annular space to the annulus when the first piston is in the first position.

15. The completion system according to claim 13 , wherein the valve assembly has a second piston moving in a second bore between a first position and a second position, the second bore having a first opening in fluid communication with the second opening of the first bore, and the second bore having a second opening in fluid communication with the annular space.

16. The completion system according to claim 15 , wherein the second bore has a third opening in fluid communication with the annulus for venting of pressure in the annular space to the annulus when the second piston is in the second position.

17. The completion system according to claim 15 , the valve assembly having a second breakable element for maintaining the second piston in the first position.

18. A completion system for completing a well having a top, comprising:

a borehole,

a first well tubular metal structure,

a second well tubular metal structure comprising at least one annular barrier having a tubular part mounted as part of the second well tubular metal structure and surrounded by an expandable metal sleeve, expandable by means of pressurised fluid from within the second well tubular metal structure through a valve assembly into an annular space between the tubular part and the expandable metal sleeve, the second well tubular metal structure having a first end closest to the top and a second end, the valve assembly having a first condition in which fluid communication between an inside of the second well tubular metal structure and the annular space is disconnected, and having a second condition allowing fluid communication between the inside of the second well tubular metal structure and the annular space,

a first delivering means for delivering cleanout fluid at a first pressure through the second well tubular metal structure, and

a second delivering means for delivering cement at a second pressure through the second well tubular metal structure,

wherein the valve assembly comprises a breakable element breakable at a third pressure being higher than that of the first pressure and of the second pressure, enabling the valve assembly to change from the first condition to the second condition, and

wherein the first condition is a first position and the second condition is a second position, and the valve assembly comprises a first piston moving in a first bore between the first position and the second position, the first piston being maintained in the first position by means of the breakable element, and the first bore having a first opening in fluid communication with an inside of the second well tubular metal structure, and a second opening in fluid communication with the annular space.

19. The completion system according to claim 18 , wherein the first bore has a third opening in fluid communication with the annulus for venting of pressure in the annular space to the annulus when the first piston is in the first position.

20. The completion system according to claim 18 , wherein the valve assembly has a second piston moving in a second bore between a first position and a second position, the second bore having a first opening in fluid communication with the second opening of the first bore, and the second bore having a second opening in fluid communication with the annular space.

21. The completion system according to claim 20 , wherein the second bore has a third opening in fluid communication with the annulus for venting of pressure in the annular space to the annulus when the second piston is in the second position.

22. The completion system according to claim 20 , the valve assembly having a second breakable element for maintaining the second piston in the first position.