Method and system for integrity testing

1. A method for testing an integrity of a primary barrier arranged in a well, wherein the method comprises:

arranging a first sealing device above the primary barrier in a position axially spaced from the primary barrier in the well, thereby establishing a test chamber confined by the first sealing device and the primary barrier;

arranging a second sealing device above the first sealing device in a position axially spaced from the first sealing device in the well, thereby establishing a further test chamber between the first sealing device and the second sealing device;

reducing a pressure of the test chamber to a predetermined test pressure;

monitoring the pressure of the test chamber and a pressure of the further test chamber after the pressure reduction; and

verifying the integrity of the primary barrier if the following conditions are fulfilled:

no pressure increase is detected in the test chamber after the applied pressure reduction; and

no pressure decrease is detected in the further test chamber after the applied pressure reduction.

2. The method according to claim 1 , where the method further comprises retrieving the first sealing device and the second sealing device from the well after verifying the integrity of the primary barrier.

3. The method according to claim 1 , where reducing the pressure of the test chamber comprise:

providing the first sealing device with a tank device having a chamber filled with a gas with a pressure lower than a pressure in the well; and

establishing fluid communication between the chamber of the tank device and the test chamber.

4. The method according to claim 3 , where providing the first sealing device with a tank device having a chamber filled with a gas with a pressure lower than the pressure in the well comprises:

establishing fluid communication between the chamber of the tank device and topside surroundings, before the first sealing device is lowered into the well; and

closing the fluid communication to a chamber topside, before the first sealing device is lowered into the well.

5. The method according to claim 1 , where the method further comprises:

verifying a failed integrity of the second sealing device if a pressure decrease is detected in the further test chamber after the applied pressure reduction.

6. A system for testing integrity of a primary barrier arranged in a well; wherein the system comprises:

a first sealing device provided for arrangement above the primary barrier in a position axially spaced from the primary barrier for establishing a confined test chamber between the first sealing device and the primary barrier;

a second sealing device provided for arrangement above the first sealing device in a position axially spaced from the first sealing device for establishing a further confined test chamber between the first sealing device and the second sealing device;

a pressure reducing device configured for reducing a pressure of the test chamber to a predetermined test pressure;

a monitoring arrangement comprising a first sensor and communication device arranged for surveying the pressure of the test chamber after the pressure reduction and a second sensor and communication device arranged for surveying a pressure of the further test chamber after the pressure reduction; and

a pressure testing device provided in communication with the first and second and communication devices, where the pressure testing device is configured for testing and verifying an integrity of the first sealing device and the integrity of the primary barrier.

7. The system according to claim 6 , where the pressure testing device is configured to verify the integrity of the primary barrier if the following conditions are fulfilled:

no pressure increase is detected in the test chamber after the applied pressure reduction; and

no pressure decrease is detected in the further test chamber after the applied pressure reduction.

8. The system according to claim 6 , where the pressure reducing device comprises:

a fluid tank housing with a fluid compartment;

a fluid line providing fluid communication between an outside of the fluid tank housing and the fluid compartment; and

a valve arrangement provided in the fluid line.

9. The system according to claim 8 , where the pressure testing device is configured to control the valve arrangement.

10. The system according to claim 8 , where the pressure reducing device comprises:

a nose section releasable connected to the fluid tank housing for providing access to the fluid compartment; and

a volume reducing insert into the fluid compartment for reducing the volume of the fluid compartment.

11. The system according to claim 8 , where the fluid compartment is filled with gas with atmospheric pressure before an integrity testing operation starts.

12. The system according to claim 6 , where the first and second sealing devices are mechanically connected to each other and are set during one run.

13. A method for testing an integrity of a primary barrier arranged in a well, wherein the method comprises:

arranging a first sealing device above the primary barrier in a position axially spaced from the primary barrier in the well, thereby establishing a test chamber confined by the first sealing device and the primary barrier;

arranging a second sealing device above the first sealing device in a position axially spaced from the first sealing device in the well, thereby establishing a further test chamber between the first sealing device and the second sealing device;

reducing a pressure of the test chamber to a predetermined test pressure comprising:

providing the first sealing device with a tank device having a chamber filled with a gas with a pressure lower than a pressure in the well; and

establishing fluid communication between the chamber of the tank device and the test chamber;

monitoring the pressure of the test chamber and a pressure of the further test chamber after the pressure reduction; and

verifying the integrity of the primary barrier if the following conditions are fulfilled:

no pressure increase is detected in the test chamber after the applied pressure reduction; and

no pressure decrease is detected in the further test chamber after the applied pressure reduction.

14. A system for testing an integrity of a primary barrier arranged in a well; wherein the system comprises:

a first sealing device provided for arrangement above the primary barrier in a position axially spaced from the primary barrier for establishing a confined test chamber between the first sealing device and the primary barrier;

a second sealing device provided for arrangement above the first sealing device in a position axially spaced from the first sealing device for establishing a further confined test chamber between the first sealing device and the second sealing device;

a pressure reducing device configured for reducing a pressure of the test chamber to a predetermined test pressure, wherein the pressure reducing device comprises: a fluid tank housing with a fluid compartment; a fluid line providing fluid communication between an outside of the fluid tank housing and the fluid compartment; and a valve arrangement provided in the fluid line;

a monitoring arrangement comprising a first sensor and communication device arranged for surveying the pressure of the test chamber after the pressure reduction and a second sensor and communication device arranged for surveying a pressure of the further test chamber after the pressure reduction; and

a pressure testing device provided in communication with the first and second and communication devices, where the pressure testing device is configured for testing and verifying an integrity of the first sealing device and the integrity of the primary barrier.