Well Integrity Technical Section

Folks,

 

I am trying to gauge peoples opinions on using VR plugs as a long term barrier where no gate valve is installed? The case that I am thinking of, is on the non-active side of the wellhead, where you fit a VR plug in place, followed by a blanking plate, complete with a NPT fitting and needle valve and pressure gauge.

 

Depending on your response, would it matter if this is the “A”, “B”, “C”, etc. annuli

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Stuart Wardlaw
Well Engineer
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Stuart,
If you're going to do this, which is quite acceptable, install the VR plug on one side only and put a Gate valve on the other side. That way, you can always circulate the well as required for whatever reason.
And it's good for any annulus.

Regards
Stuart Liddle
Consultant

------Original Message------

Folks,

 

I am trying to gauge peoples opinions on using VR plugs as a long term barrier where no gate valve is installed? The case that I am thinking of, is on the non-active side of the wellhead, where you fit a VR plug in place, followed by a blanking plate, complete with a NPT fitting and needle valve and pressure gauge.

 

Depending on your response, would it matter if this is the “A”, “B”, “C”, etc. annuli

------------------------------
Stuart Wardlaw
Well Engineer
------------------------------

Stuart,

Thanks for your input. Indeed, this is the example that I was thinking of when I wrote the post, and should have been a little more clearer

Thanks

Stuart

------------------------------
Stuart Wardlaw
Well Engineer
------------------------------

Original Message:
Sent: Jul 09,2015 04:02 AM
From: Stuart Liddle
Subject: Use of VR plugs

Stuart,
If you're going to do this, which is quite acceptable, install the VR plug on one side only and put a Gate valve on the other side. That way, you can always circulate the well as required for whatever reason.
And it's good for any annulus.

Regards
Stuart Liddle
Consultant

Stuart,

There shouldn't be anything wrong with a VR plug as a long term barrier in principle, but there are a few things puzzling me:

• You're installing a barrier element without testing & qualifying it (your annulus is not live).
• Then you put your blanking plug as a backup, with a pressure gauge to detect whether the VR plug has failed.
• If the annulus becomes live at some point you won't know it unless the VR plug fails or you remove it.
• If there is no pressure, you can always remove the blanking plate then play with the VR plug through a lubricator, but what if you measure a leak through your gauge? Then what do you do (since you know your primary and secondary barriers have failed but not your third one - the blanking plate, valve and gauge)?

I would feel more comfortable with doing this on B+ annuli but not the A annulus: it has a tendency to fail (packer and tubing mostly) and most failures will result in a large potential flow rate. If outer annuli come live, the majority of leaks will be small (through cement), so easier to control if the VR plug fails.

Best regards,

Matteo

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Matteo Loizzo
Well integrity consultant
Berlin
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Matteo,

Thanks for your reply. I could have been more specific in my original posting and apologise for this. This would only be on the non-active side, while the active side would have a gate valve, etc. in place.

Thanks

Stuart

------------------------------
Stuart Wardlaw
Well Engineer
------------------------------

Original Message:
Sent: Jul 09,2015 06:41 AM
From: Matteo Loizzo
Subject: Use of VR plugs

Stuart,

There shouldn't be anything wrong with a VR plug as a long term barrier in principle, but there are a few things puzzling me:

• You're installing a barrier element without testing & qualifying it (your annulus is not live).

• Then you put your blanking plug as a backup, with a pressure gauge to detect whether the VR plug has failed.

• If the annulus becomes live at some point you won't know it unless the VR plug fails or you remove it.

• If there is no pressure, you can always remove the blanking plate then play with the VR plug through a lubricator, but what if you measure a leak through your gauge? Then what do you do (since you know your primary and secondary barriers have failed but not your third one - the blanking plate, valve and gauge)?

I would feel more comfortable with doing this on B+ annuli but not the A annulus: it has a tendency to fail (packer and tubing mostly) and most failures will result in a large potential flow rate. If outer annuli come live, the majority of leaks will be small (through cement), so easier to control if the VR plug fails.

Best regards,

Matteo

------------------------------
Matteo Loizzo
Well integrity consultant
Berlin
------------------------------

Generally I agree that it's an acceptable barrier in the operations I've been involved with, particularly short - medium term, however there's some interesting issues.

1. If used in the A annulus is it installed in a well with a packer and kill weight fluid or is there no packer and a live annulus. What are your "two barriers" & your barrier policy? Packer fluid isn't always kill weight!

2. I'm not sure what type of thread a VR plug has, perhaps LP (NPT?) and typically < 2".  This leads to questions about the long term.  integrity of the thread, similar to questions raised about BTC, STC, LTC, EUE,etc. What sealant / lubricant / tape , if any? 

3. What pressure rating is the casing head or spool? I think 2" threaded connections are limited to 3k or maybe 5k. The VR is just <2" so ???

4. I recall hot tapping some solid bull plugs way back and probably the VR plugs too to check for pressure. Always run a tapped bull plug in that scenario over a VR plug.

5. I also recall there are different styles of VR plugs. One's solid. Another type I think you can insert what I call a Vaetrix nipple (I've also heard it called a Taylor plug) to check for pressure under the VR. This results in additional potential leak paths (o-rings, Check valve, etc).

6. The VR plugs are tested in the factory as part of the head / spool manufacture however in the field it might be removed for circulation and  it might not be possible to re validate the re installation.

7. I agree could be used in any annulus subject to a P limit (<= 5k) but usually on A annulus it's useful having pressure or flow / pump access on both sides.

Terry Greaney

Consultant

Brisbane

Original Message:
Sent: Jul 09,2015 06:49 AM
From: Stuart Wardlaw
Subject: Use of VR plugs

Matteo,

Thanks for your reply. I could have been more specific in my original posting and apologise for this. This would only be on the non-active side, while the active side would have a gate valve, etc. in place.

Thanks

Stuart

------------------------------
Stuart Wardlaw
Well Engineer
------------------------------

Terry, thanks for your input and raising a few interesting points for me to clarify with both clients and suppliers in the future

------------------------------
Stuart Wardlaw
Well Engineer
------------------------------

Original Message:
Sent: Jul 09,2015 08:15 AM
From: Terry Greaney
Subject: Use of VR plugs

Generally I agree that it's an acceptable barrier in the operations I've been involved with, particularly short - medium term, however there's some interesting issues.

1. If used in the A annulus is it installed in a well with a packer and kill weight fluid or is there no packer and a live annulus. What are your "two barriers" & your barrier policy? Packer fluid isn't always kill weight!

2. I'm not sure what type of thread a VR plug has, perhaps LP (NPT?) and typically < 2".  This leads to questions about the long term.  integrity of the thread, similar to questions raised about BTC, STC, LTC, EUE,etc. What sealant / lubricant / tape , if any? 

3. What pressure rating is the casing head or spool? I think 2" threaded connections are limited to 3k or maybe 5k. The VR is just <2" so ???

4. I recall hot tapping some solid bull plugs way back and probably the VR plugs too to check for pressure. Always run a tapped bull plug in that scenario over a VR plug.

5. I also recall there are different styles of VR plugs. One's solid. Another type I think you can insert what I call a Vaetrix nipple (I've also heard it called a Taylor plug) to check for pressure under the VR. This results in additional potential leak paths (o-rings, Check valve, etc).

6. The VR plugs are tested in the factory as part of the head / spool manufacture however in the field it might be removed for circulation and  it might not be possible to re validate the re installation.

7. I agree could be used in any annulus subject to a P limit (<= 5k) but usually on A annulus it's useful having pressure or flow / pump access on both sides.

Terry Greaney

Consultant

Brisbane



Original Message:
Sent: Jul 09,2015 06:49 AM
From: Stuart Wardlaw
Subject: Use of VR plugs

Matteo,

Thanks for your reply. I could have been more specific in my original posting and apologise for this. This would only be on the non-active side, while the active side would have a gate valve, etc. in place.

Thanks

Stuart

------------------------------
Stuart Wardlaw
Well Engineer
------------------------------