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Casing leakage (now confirmed as stage collar)
12 May 2019
Dear colleagues,

We have lowered 244.5 x 11.99 mm (9 5/8 x 
0.472 inch) casing at depth 4560 m with the multistage cement collar at 1975 m at our well. After that we conduct two stage of cementing and pump slurry from bottom to surface. Now we get a problem with pressure test for casing lower section and we looking for leakage.

Could you suggest some effective tool tool seal it? After, of course, we find it. Next section bit will be 215.9 mm (8 1/2 inch) and production casing will be 177.8 mm (7 inch) with the 194.4 (7.656 inch) coupling.       

Thank you
16 answer(s)
SPREAD Associates
Total Posts: 39
Join Date: 16/08/10
What do the Ukraine regulations actually say ?: do they also specify quality of cement slurries to surface? returns ?  If your squeeze worked, presumably you did have good cement behind pipe to squeeze into .
I have seen the same practice elsewhere in FSU and resultant logistics. Did such regulations arise  because it was the the Soviet Union and not very concerned with time and costs-or more to it ?
Drilling Engineer
DTEK Oil&Gas
Total Posts: 12
Join Date: 25/02/19
Dear colleagues thanks a lot for the many helpful suggestions. We've done a squeeze cementing, WOC, drill out cement and perform pressure test at 200 bar to make sure that the whole casing is ok (leakproof). Regretfully we have to cement our wells to the surface because of Ukrainian legislative. That's why we are using cement collar. But now we are looking for alternatives (lite cement or smth). We've sdone some changes in well design because of this situation. After drilling next section we'll run tieback together with 7' liner. Best regards, Yevhenii
Well Specialist
Health & Safety Executive
Total Posts: 4
Join Date: 12/05/16
Hi  Yevhenii
Polymer based epoxy has been used in reservoir management , including water shut off , zonal isolation , etc. It is basically a wireline conveyed tool that can perforate the casing and inject the sealant ( Epoxy) into the annulus. Also, it can be injected into poorly cemented annuli. You may consult with the service providers to find out whether it is applicable for your case.

Pete Thomson
Decommissioning Manager
Baker Hughes
Total Posts: 16
Join Date: 12/12/15

Hi Les - BiSN is your company which is developing this technology.  I guess that, since this is a thermite activated alloy, the Bi stands for Bismuth and SN stands for tin. was our contact


SPREAD Associates
Total Posts: 2
Join Date: 18/09/16
what is Bismuth?
who sells it?
Managing Director
Vartech Eng
Total Posts: 22
Join Date: 06/07/15
Hi Yevhenii,

If you can not work out how to live with that leak and/or the solutions mentioned before (cement 
squeeze jobs, resins) fail, my suggestion is to be prepared to run another casing string (i.e. f7-5/8" casing / liner), and you would have to give up a potential contingency and hole size.

Also, be prepared with double-side valves in the wellhead to deal with a potential live annuli / surface pressure.

If you can live with the leak thru the DV tool (i.e. enough FIT/LOT to drill the next section), you may consider to drill the next section and run either a tieback or a casing patch later on.

Hope you can get a good solution for this challenge.

Thanks and regards,
Reynaldo Vargas
Well Engineer
Total Posts: 25
Join Date: 17/09/07
Given it is the stage collar, other leak paths are available, you now have to approach it from a well integrity POV.   Remedial work, from squeezing et al, might work.  Additionally you might be able to get a patch, logistics aside, but that could cause more problems:-
Still cannot hold sufficient pressure
Drift issues
Patch not staying in place....

Additionally do you have any issues with the existing TOC i.e has the well architecture requirements for the stage collar been achieved?

Bottom line is you will be unlikely to get back to full integrity, for the next phase, but you should look at long term integrity.

Can you bring the top of the 7" liner above the stage collar for long term production?  At these depths it's basically a tieback...

Can you drill the next section with the leak active (Treat it like a shoe strength - LOT & Kick tolerance & potential leak up the back side), with lots of risk mitigations in place?
Can you set the 7" as a scab liner and still achieve the well objective?
However painful, you have a deep shoe and a leak halfway up, so can you live with the leak?

Drilling Specialist/Well Engineer/Training Consultant
Kingdom Drilling
Total Posts: 502
Join Date: 10/01/05
As is being used successfully in abandonments to seal and verify well integrity may be applicable particularly where leak is a very miniscuble leak path. Bismuth will plug this. Excess if present on pipe ID can be readily milled out is my understanding.
Total Posts: 22
Join Date: 01/09/12
Resin application (if you can get it) can help as well. ControlSeal from WWClooks promising from the studies we have done for our case.
(retired) Well Fluids Team leader
SPREAD Associates
Total Posts: 57
Join Date: 14/06/06

I was interested in why you are having to use a stage collar?
Is this casing critical to the well delivery?
What was the planned height of cement above the collar ? 

What is your mud type and weight ?
Can you wait for your patch and do another well in the meantime? 

A) If casing is not critical is it worth considering punching holes in your casing higher up so you can establish circulation around the casing ?  Do you know if you actually have got any cement above the stage collar ? 

B) Also is it possible to establish that you can actually squeeze a clear fluid in to your stage collar before going to the cementing squeeze option as suggested by Paul 

I have not seen much success with cement squeezes (<20%) after a primary cementing failure unless you can circulate.   

Regards Ian 
Total Posts: 117
Join Date: 10/04/08
I really think you need some 9.5/8" drillable bridge plugs and cement retainers to squeeze cement at the stage collar effectively. They are off the shelf items in Europe.

Have your cementing provider work on a squeeze slurry design for you. The second stage cement slurry design is probably not suitable.

Try to use 2.7/8" tubing as a balanced cement plug stinger? It would be better than using drill pipe, but 3.1/2" drill pipe will be better than using 5".

You need to set a good long hi vis pill below the stage collar to act as a good plug base, then a good length cement plug from below the stage collar to well above it, consider 1000ft, then pull the stinger out slowly, then close BOP and squeeze 1/2 the cement into the stage collar, and then stop and wait 30 mins then squeeze a bit more then wait then squeeze more until its clear you are getting a pressure build up. Leave cement in the casing to drill out.

Drilling Engineer
DTEK Oil&Gas
Total Posts: 12
Join Date: 25/02/19
Hi Dave, yes before the prime cement job we plan to run the packer to test and comfirm the leak at the stage collare.
Managing Director (
Relentless Pursuit Of Perfection Ltd.
Total Posts: 484
Join Date: 10/01/05

I take it that you are also discussing with the provider of the stage collar, to identify what more you can do before you go down this road (cement).

Did you use some kind of test packer to determine the source of the leak? Or just the temperature log?

If you have a test packer (RTTS, DLT or equivalent) you could do the same as Paul Howlett suggests. (I can't imagine drilling a well without access to such a packer, given the consequences of not having).

I hope that helps

Drilling Engineer
DTEK Oil&Gas
Total Posts: 12
Join Date: 25/02/19

Dear Forum members - an update on my earlier post

 We ran a temperature log and  have a hole in the stage collar in 9 ⅝” casing and failed to pressure test the same. The casing is set at 4560m and the collar is at 1960m.

For remedial job, we plan to squeeze cement across the color. Due to limited market in Ukraine, we do not have bridge plugs nor do we have cement retainers of this size or any other casing patches in country. Mobilizing any of them will take weeks. 

Hence, we think to squeeze above a heavy pill. What are your thoughts and best practices to achieve success from the first time?

For information prior to temperature log we have pumped 11m3 of fluid into the hole and returned 1.5 m3. Apparently, we fracture the previous casing shoe at 2200m.

Appreciate your help!

Total Posts: 117
Join Date: 10/04/08
Yevhenii, It has been a long time since I heard of newly run casing, assuming premium connections, leaking directly after running and cementing. I'd suggest its unlikely to be the casing itself, unless you have non-premium connections and/or did not make them up correctly. I believe its more likely, based on the limited information you have provided, that your shoe track is leaking or the stage collar is leaking. As some stage you are going to have to drill out the sleeves in the stage collar anyway, so I'd run in, try to go through the closing sequence with the bit by applying weight, then drill out the plugs and sleeves, then try a pressure test on the whole casing again, if it leaks run a cement retainer, not a bridge plug, but a cement retainer to the bottom of the casing above the shoe track, then pressure test it again, if it holds you know its a shoe track leak and you can run drill pipe and sting in and do a cement job, if it leaks still I still think its likely to be the stage collar so you need to run an RTTS type packer, set it below the stage collar and test again, if you run a stinger of 3.1/2" DP of 1000-2000ft below the RTTS then you could do a cement job across the stage collar and squeeze away cement to repair it potentially. If the stage collar is not leaking you have to go up and down the casing pressure testing looking for leaks, but with a set cement retainer at the bottom its unlikely to be leaking via the shoe track. Good luck, come back and let the group know how you get on. Paul
SPREAD Associates
Total Posts: 17
Join Date: 26/09/13
It is possible that the stage collar closing sleeve has not fully moved.

A run with a full size (not drift) bit/mill will close the tool. If the part of shoe track was drilled, on of the bottom casing joints could have backed-off. Location of leak many bring more suggestions.

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