Barrier testing method

1. A barrier testing method for testing a production casing in a borehole, the method being applied before initiating production in a well, the method comprising:

connecting a drill pipe with a first end of a first production casing having annular barriers, which annular barriers comprise a tubular part forming part of the casing and an expandable sleeve circumferenting the tubular part, thereby defining an expandable space,

inserting the drill pipe and the first production casing via a drill head arranged at a top of the well into an intermediate casing extending in a first part of the borehole closest to the top of the well and at least part of the first production casing into a second part of the borehole,

sealing a second end of the first production casing,

pressurising the first production casing from within and expanding one or more of the expandable sleeves of the annular barriers to abut a wall of the borehole,

pressurising the first production casing from within to a predetermined pressure, and

testing the first production casing after expansion by measuring if the predetermined pressure is kept constant during a predetermined time period, while the second end of the first production casing is sealed.

2. A barrier testing method according to claim 1 , further comprising:

setting a first barrier packer between the first production casing and the intermediate casing,

disconnecting the drill pipe,

pressurising the first production casing and the intermediate casing from within to a second predetermined pressure, and

testing the first barrier packer by measuring if the second predetermined pressure is kept constant during a predetermined time period.

3. A barrier testing method according to claim 2 , further comprising:

inserting a second production casing into the well, the second production casing having a plug arranged within a second production casing and a downhole safety valve arranged within the second production casing closer to the top of the well than the plug,

setting a second barrier packer in an annular space between the second production casing and the intermediate casing,

pressurising the annular space from within to a third predetermined pressure, and

testing the second barrier packer by measuring if the third predetermined pressure is kept constant during a predetermined time period.

4. A barrier testing method according to claim 3 , further comprising:

opening the downhole safety valve,

pressurising the second production casing from within to a fourth predetermined pressure, and

testing the plug by measuring if the fourth predetermined pressure is kept constant during a predetermined time period.

5. A barrier testing method according to claim 4 , further comprising:

closing the downhole safety valve,

pressurising the second production casing above the downhole safety valve from within to a fifth predetermined pressure, and

testing the downhole safety valve by measuring if the fifth predetermined pressure is kept constant during a predetermined time period.

6. A barrier testing method according to claim 5 , further comprising:

replacing the drill head with a well head,

pressurising the annular space from within to a sixth predetermined pressure, and

testing the second barrier packer by measuring if the sixth predetermined pressure is kept constant during a predetermined time period.

7. A barrier testing method according to claim 6 , further comprising:

pressurising the second production casing above the downhole safety valve from within to a seventh predetermined pressure, and

testing the downhole safety valve by measuring if the seventh predetermined pressure is kept constant during a predetermined time period.

8. A barrier testing method according to claim 1 , wherein cement is provided between the intermediate casing and the borehole and the intermediate casing comprises at least two annular barriers, and before the first production casing is arranged in the well, the annular barriers of the intermediate casing are expanded to abut the wall of the borehole, thereby displacing the non-cured cement so that a pressure increase is created between the annular barriers, the method further comprising testing the annular barriers by monitoring the pressure increase for a period of time.

9. A barrier testing method according to claim 7 , wherein the intermediate casing comprises an annular barrier, and before the first production casing is arranged in the well, the annular barriers of the intermediate casing are expanded to abut a second intermediate casing arranged outside the intermediate casing, whereby a second annular space is provided above and between the intermediate barriers and the second intermediate barrier, the method comprising:

pressurising the second annular space from within to an eighth predetermined pressure, and

testing the annular barrier by measuring if the eighth predetermined pressure is kept constant during a predetermined time period.

10. A barrier testing method according to claim 1 , further comprising rotating the first production casing while inserting the same.

11. A barrier testing method according to claim 1 , wherein, before sealing the second end of the first production casing is initiated, the first production casing is pressurised with a flushing fluid so that the flushing fluid is injected from the second end of the first production casing for flushing drilling mud outside the first production casing.

12. A barrier testing method according to claim 1 , wherein pressurising the first production casing from within to a predetermined pressure is performed by pressurising fluid into the well from the top of the well.

13. A barrier testing method according to claim 1 , wherein sealing the second end of the first production casing is performed by dropping a ball into the first production casing, the ball being adapted to seal off an opening provided at the second end of the first production casing.

14. A barrier testing method according to claim 1 , further comprising providing apertures in the first production casing to allow fluid communication between the borehole and the casing.

15. A barrier testing method according to claim 14 , further comprising injecting stimulation fluid out through the apertures into the borehole to perform stimulation of the borehole.

16. A completion system for oil production from a well, adapted for carrying out the method according to claim 1 .