Good day dear colleagues.
I am included into a team to write a company standard about our ”œBarrier Philosophy”.
Some of us are stipulating that we can use a SCSSSV as a barrier (for workovers, well interventions etc.), once it was positively inflow tested with a zero leak rate. There are companies, but not all of them, whose policies or standards are not allowing that.
Now, is there a good academic reason or
technical explanation for allowing one or the other?
I would like to get your opinion on that subject. Also, if you can´t give me a good academic reason or technical explanation to go for one or the other, could you tell me how your company is dealing with this question and who that company would be?
Thank you very much for your time spent on reading this question already now!
My original question was ”œdoes a barrier have to be tested and meet V0” as it seems to me that the term V0 often gets used incorrectly and often totally in the wrong context.
Not so long ago I read a request for a V0 bridge plug to be used within a well with BTC casing, EUE tubing, and at best a V3 but probably V5 production packer.
So I guess Ifor, your comments are right that ”œa barrier does not have to be V0. The rating required is dependent on the well conditions”.
So for clarification, are you saying that a BOP or an RTTS type packer or a wireline plug or bridge plug to be considered a ”œbarrier” must meet the criteria of ISO 14310 qualification testing as below?
Testing a barrier at high and low pressures does not constitute V0.
V6 - Supplier/manufacturer defined
V5 - Liquid test
V4 - Liquid test + axial loads
V3 - Liquid test + axial loads + temperature cycling
V2 - Gas test + axial loads
V1 - Gas test + axial loads + temperature cycling
V0 - Gas test + axial loads + temperature cycling + zero bubbles leakage
This is a very interesting discussion and I have a question regards the statement made by Chris in his response. Does a barrier really have to be V0?
Thank you very much Mike, Ruari and Chris,
For your answers, they were very helpful so far in having further thoughts.
Chris, thank you very much for the hint with the NORSOK D010! The NORSOK D010 is mentioning the DHSV (Down Hole Safety Valve) nine (9) times in the schematics, where it is part of the well barrier envelope:
- Of which are four (4) for production or injection wells.
- One (1) is showing a DHSV for pulling a BOP and landing a tree, with a mechanical plug set below (So how would you now inflow test the DHSV?) and a ”œdebris plug” set into the tubing hanger profile, preventing the concerns of Mike, that something drops on the DHSV and opens it (see Page 69 of NORSOK D010).
- Three (3) times the DHSV is used for isolation purposes: rigging up wireline, CT-equipment or snubbing equipment above a surface tree (XT).
- And the DHSV is mentioned once (1) for pumping into the well, if tree (XT) isolation tools are installed in the XT.
On page 162 the NORSOK D010 (definitions table for the well barrier elements) is than talking about the leak rates acceptable by the DHSV as indicated by you Ruari and Mike (you were very close with your top of the head figures Ruari):
a) 0,42 Sm3/min (25,5 Sm3/hr) (900 scf/hr) for gas;
b) 0,4 l/min (6,3 gal/hr) for liquid.
Is that not strange? I would not accept a leaking barrier.
I believe there is/are still not yet an academic or a technical sound answer(s) to go for one or the other direction, is there?
Thank you very much gents for your feedback and input so far!
It's not so much that they normally leak (Mike's usually correct assertion) but rather that they are not designed NOT to leak. Can't quote the actual API spec but an SCSSSV, by design, can have an acceptable leak rate. This is also reflected in the views of various regulatory bodies. Off the top of my head it is 0.43 cubic meters / min of gas or 0.400 cubic meters/min of liquid.
So that's the technical reason to say no to their use as a barrier.
Having said that, I am sure certain brands are designed to be 'zero leak' and indeed some may be very reliable. Additionally you can test one to your satisfaction.
As a first pass some companies are accepting a new, shop tested SCSSSV as a barrier for installation (No plug needed downhole in the tubing while putting your XT on). Some take this further and accept a robustly test (Inflow tested?) SCSSSV to take a XT off. Not sure if you would find anyone accepting a leaking one.....
In all cases, this would be as a second barrier. If this was your only barrier, it would depend on your assessment of the risk. As Mike alludes to dropping toolstrings might be riskier than pulling a XT off with a well on static / low losses and plenty of brine on location.
Any barrier policy would have to make some form of table when it was acceptable and under what circumstances. Cos sure as God made little apples, you say it can be used as a barrier, one of your company men will whip off a tree with a leaking SCSSSV saying 'but API accepts a leak"
I'm working as a Well Examiner at present
There is a school of thought that says a SCSSSV should not be used as a barrier, but its mainly related to the fact that they will normally leak! So if you require a zero leak rate, then in my opinion its perfectly logical.
I am the well integrity authority, and I guess its up to me! You may have to think about if you want to specify something other than a zero leak rate. Also if the safety valve is the only barrier, and you are using it to deploy a toolstring, then a dropped toolstring would open it, at which point you have a problem. If you have a tree valve closed, and its not exposed to a dropped object then that's a different case.