Method of plugging and pressure testing a well

1. A method of plugging a well extending into a formation to facilitate temporary or permanent abandonment of the well, the method comprising:

conveying a plug placement and verification tool (PPVT) through the well, to a plug formation location, the PPVT comprising a stinger for delivering a plugging material into the well, an expandable packer disposed at one end of the stinger and a pressure sensor disposed below the expandable packer;

operating the expandable packer to form a seal in the well above the pressure sensor;

delivering a plugging material from the stinger into a region of the well above the expandable packer, thereby forming a plug in the well; and

thereafter creating a pressure change above the plug and verifying the integrity of the plug using the pressure sensor.

2. The method according to claim 1 , further comprising, prior to said step of conveying the PPVT to the plug formation location, installing a mechanical plug or packer below the plug formation location.

3. The method according to claim 2 , wherein the mechanical plug is a bridge plug.

4. The method according to claim 2 , said mechanical plug or packer being installed across the full extent of the casing or within a liner remaining within the casing.

5. The method according to claim 2 , further comprising, prior to said step of conveying, forming openings in a well casing to expose the formation at least at a first upper location and a second lower location, wherein:

the mechanical plug or packer is installed below the second location; and

the expandable packer is sealed against a section of the casing, or against a liner within the casing, between the first and second locations.

6. The method according to claim 1 , wherein said step of verifying the integrity of the plug comprises detecting changes in an output signal provided by the pressure sensor.

7. The method according to claim 1 , wherein the PPVT further comprises one or more temperature sensors and the method further comprises utilizing the one or more temperature sensors to monitor the plugging material hydration during or following said step of delivering the plugging material from the stinger.

8. The method according to claim 1 , wherein a signal from the pressure sensor is transmitted to the wellhead through or via the stinger of the PPVT.

9. The method according to claim 1 , wherein the PPVT is conveyed on a wireline or drillpipe.

10. The method according to claim 1 , further comprising leaving the stinger in situ following delivery of the plugging material, thereby forming part of the plug once set.

11. The method according to claim 10 , wherein, following placement of the plug, the stinger provides a communication path, through the set plug, for signals output by the sensor(s).

12. The method according to claim 1 , further comprising, prior to said step of delivering, disconnecting the stinger from the expandable packer and pressure sensor and, after placement of the plugging material, retrieving the stinger to the surface on the wireline or drill pipe whilst leaving the pressure sensor in place.

13. The method according to claim 1 , further comprising vibrating the stinger during said step of delivering.

14. The method according to claim 1 , wherein said stinger comprises a cup packer located above injection nozzles provided in the stinger, the cup packer increasing the plugging material injection pressure.

15. The method according to claim 1 , wherein the step of delivering the plugging material and forming the plug in the well and the step of verifying the integrity of the plug using the pressure sensor are performed in a same trip of the PPVT.

16. The method according to claim 1 , wherein the pressure sensor remains disposed below the expandable packer after the plug is formed by the step of delivering the plugging material, and the pressure sensor is disposed below a distal end of the stinger and thus below the entirety of the plugging material forming the plug.

17. The method according to claim 1 , further comprising the steps of:

prior to said step of conveying the PPVT to the plug formation location, installing a mechanical plug or packer below the plug formation location; and

forming a plurality of perforation zones to expose the formation,

wherein the mechanical plug or packer is situated below a lowest perforation zone of the plurality of perforation zones, and the expandable packer is situated above said lowest perforation zone but below a penultimate perforation zone of the plurality of perforation zones, such that an interval between the expandable packer and the mechanical plug or packer acts as a small test volume which enables highly-sensitive monitoring of the integrity of the plug.

18. A method of plugging a well extending into a formation to facilitate temporary or permanent abandonment of the well, the method comprising:

conveying a plug placement and verification tool (PPVT) through the well, to a plug formation location, the PPVT comprising a stinger for delivering a plugging material into the well, an expandable packer disposed at one end of the stinger, and one or more sensors;

operating the expandable packer to form a seal in the well;

delivering a plugging material from the stinger into a region of the well above the expandable packer, thereby forming a plug in the well; and

thereafter leaving the stinger in situ to provide a communication path, through the set plug, for signals output by the sensor(s).