Hey Dhyaa,
I couldn't see any details regarding the production tubing string.
Is the wellhead made up to the surface casing or only to the 13 5/8 in.? I could see the 18 3/8 in. surface casing eroded, everything is in tension. The you apply 3,000 psi upsetting the equilibrium that had built up over time. Surface casing gives way and it collapses. If your surface casing is 18 3/8 in., then you won't have a lot of steel for a 17 1/2 in. ID (drift), likely a 17.6xx in. ID. This makes for a rather thin casing to hold the weight of the well.
This is all speculation but makes for a plausible story. If you want a complete and relevant analysis, you'd have to provide the well design, EOWR, cement top and type, casing details, formation details and any aquifers, CBL/SBT/USIT logs, etc.
Is there any pressure on the A- and B-annuli when you put 3,000 psi on the tubing? How do you get the acid down? Is there a sliding sleeve or something that you use to pump the acid as close to the formation as possible? The worry is that you may pressure up the entire well, not just the tubing. Have you tried pumping down the 13 5/8 x 18 3/8 in. annulus? Or putting any pressure on it to check its integrity? Have you checked any of the annuli for integrity? I am just fishing for more clues.
Overall, I don't think the clamp is your solution, at least, until you fully understand what's happening.
You're doing an acid squeeze, not a frac hence you're not pumping huge volumes that could cool down the entire well causing this contraction.
Anyway, I think this is about all this forum can help with. The next step is an engineering report/investigation.
All the best,
Matthias
Original Message:
Sent: 09-26-2022 04:55 AM
From: Dhyaa Alwahami
Subject: Casing Clamp
Hello,
The well situation was to acidize 50 meters of perforations, and the well was producer since 2000 and stopped at 2015. And the well architecture is surface 18 3/8", intermediate 13 5/8" and tapered production section as described above. The wellhead type is McEvoy 5k psi.
The pressure was applied over the entire well. And trying to squeeze couple of acid barrels and was 15% HCL.
The well is vertical and perfs depth below 3000 mKB.
Yes, the entire wellhead slipped down.
Unfortunately, due to availability of material and equipment, the acid job was only the job could proceed with at the current time>
Due to it's a legacy well, so there was a corrosion, but the metal loss does not exceed the accept limit.
Thanks for the valuable discussion!
------------------------------
Dhyaa Y.
"This comment / post reflects a purely personal opinion and not that of the organization with which I am affiliated."
------------------------------
Original Message:
Sent: 09-09-2022 08:56 AM
From: Matthias Kirchhoff
Subject: Casing Clamp
Hi,
Can you describe the heritage well situation? How old are we talking and what is the architecture?
I've read through the previous replies and I think that we are missing some crucial information. When you are acidizing, do you pressure up the entire well or only a section? Are you acid-fracking or simply trying to squeeze away some acid? If this is an acid frac, what rate are you pumping? I assume you are not isolating the top of the well but you are going down the production casing rather than some sort of tubing and the pressure is applied below some sort of production packer? What depth are we talking about? Is this is vertical well with perforations or a long horizontal?
If you're entire wellhead slipped down by some 50 cm, then you've got some issue. Pressure should make it grow, not contract. Your casings are very likely in tension when they were cemented in the first place and the outside bond to the formation has failed dragging the wellhead down. There might also be a case of surface/structural casing corrosion and the production and intermediate string relieve the tension by dragging down the surface casing. Fairly simple and common occurrence with surface casing. Have you checked the corrosion potential? This would be a good explanation for what happened.
The reason it happened during the acid job is that you changed the conditions and broke the final connection. There are several areas in the world where aquifers flowing past surface casing and erode them. Then one day, you find that you wellhead is held in place by the sideoutlet valves.
Other than your clamp, I don't see much of a solution. You can build a standard clamp, or use a hydraulic jacking system that you clamp to the wellhead. This is an engineering study to figure out the initial conditions and then the additional loads. Also, depending on the answers to my other questions, is acid fracking really necessary? Can you stimulate another way? Frack through tubing and isolate the top of the well? Stimulate using a straddle packer arrangement? Is an acid wash and squeeze sufficient? Acid foam frack?
Using a clamp to hold up the wellhead might be masking other more dangerous problems down the well.
Happy to discuss more.
Cheers,
Matthias