It is not worth the savings or any other reason to run buttress casing if it will be exposed to gas.
As Scott mentioned, we had quite a number of wells on several platforms with gas in the Annulus and had to be bleed off frequently. And only one wing valve at the wellhead section !!
If due to circumstances you were compelled to use an existing BTC casing string in the presence of gas I would remove the existing couplings, 100% degrease and clean and reapply them with a high quality thread locking compound, then I would design and machine some high quality metal Seal rings to place between the BTC pin ends, then ensuring the pin end is 100% grease free and clean I would make it up, again with a high quality thread locking compound. Of course I would have done some workshop trials of this process with a torque turn machine in advance to prove it up.
A simple and straightforward advice is 9 5/8" BTC casing is not at all recommended in gas wells. Always remember the life of a well is 20-25 years, so proven and tested procedure should be adopted. Even GB tubulars can be used only in intermediate casings like 13 3/8" or 16", but not for production casings.
They aren't and nope, I wouldn't!
There are/were many wells in the SNS with annulus pressure due to using BTC connections on the final string of casing.
All the best!
Reviving another thread. Buttress connections.
I've seen a few well designs where the intermediate and production casing have BTC connections. I was under the impression that they're not intrinsically gas-tight.
Would you design a well that would likely encounter a gas zone and drill the target interval with BTC connections exposed?
Abe - the short answer is: gas-tight sealability is not possible with thread dope because BTC is not a full-inteference thread, nor does it have a seal shoulder or other full contact seal characteristic.
So, you can use a thread locking conmpound, or install a ring groove, or some other option, all of which have pluses and minuses. Or just go with a gas-tight connection.
Thanks very much for the suggestions.
I will definitely look into them.
You should contact Apache in the North Sea as the Forties Field was developed with gas lift and buttress casing. They would have extensive knowledge of any problems encountered over the last 30 years.
I know of two possible solutions.
1. Texas Aria and GB Tubulars can offer a modified BTC with a seal ring in the coupling.
2. Alternatively you can look at Seal-Lube (from Hunting) which will give a gas tight seal but you have to put it on the coupling end prior to coupling makeup.
Well Ops Mgr, ENI Brazil