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Reversing out excess cement after liner cementation
24 December 2012
Hi folks

(As Santa loads up his sleigh with those gifts, I thought I'd ask a question).

At a recent DWOP, we discussed the possibility of reverse-circulating out excess cement after a liner job. The liner is equipped with a liner top packer which will be set as soon as the cement job is finished.

The advantages of doing it this way, compared to normal circulation route, being that :
  • it keeps a film of cement from the walls of the casing
  • it keeps cement away from the BOP
  • it is quicker
  • fluid interfaces with cement contamination are less and in many places that helps due to not being able to discharge this interface due to environmental considerations.
We are proposing to conduct a pressure test of the packer once it has been set and then reverse circulate out the cement.

The primary disadvantages (that we could think of) are :
  • if the packer has not set, then there's the potential to squeeze away the contents of the liner lap, and, depending where losses have occurred, the potential to cause issues with well integrity and/or zonal isolation .. so we would conduct the test in stages
  • potential to induce flash-setting of the cement (or so it is claimed), cementing in the tools
I would be interested to hear members views on the above and in particular experiences of problems caused by :
  • Cement in BOP
  • Cement flash-setting
With kind regards and wishing, those of you who celebrate it, a Merry Christmas .. and everyone Happy Holidays !!

Dave

Dave and the SPREAD team
8 answer(s)
Craig_Castille
Stone Energy
Total Posts: 8
Join Date: 21/10/10
We planned all of our jobs to reverse out excess cement. Critical to success was to establish a set time to set the LTP and test. Don't waste time. Have spacer-mud compatibility checked especially when in high mud weight. Barite drop out can stick DP just as bad as flash setting cement. Also, have your excess cement and planned cement covering the liner lap and liner top tested for extended pump time. Want to have enough time to either RO or circulate out in case the LTP (Liner Top Packer) doesn't test or the plugs don't bump.

Kind regards
Craig T. Castille
cordialdevil
Drilling Supervisor
SPREADAssociates
Total Posts: 9
Join Date: 17/08/09
A useful read about running liners is available at:
linertools.com/publications

Part 4 addresses reverse circulation.

Derek.Charlton
Drilling Engineering Mgr
Maersk Oil
Total Posts: 16
Join Date: 15/01/09
Dave,

Not much to add. Reverse circulating used to be the normal practice in my experience but the main reason things changed appeared to be the desire to pump a foam ball to clean the drill string of residual cement. I don't think cement in the BOP is of much concern as the cement is pretty well contaminated by the time it reaches the BOP (assuming you haven't pumped a large amount of excess cement). By the way, at one place I worked we never circulated the excess cement out at all on a production liner, just pulled out the hole. The view was why waste time circulating, given that you'll make a clean-out run anyway.
Graham_Falconer
Enquest
Total Posts: 4
Join Date: 17/03/10
Dave,

With regard to your post on reversing out after cementing:
  • Other than the points you make, circulating 'the long way' does not require any line-up changes; reduces the time the cement is stationary and reduces the risk of the cement setting up prematurely.
  • If reverse circulating, the line-up change should be carried out efficiently to reduce the risk of the cement setting up prematurely (I have heard tale of a rig 'phaffing about' with the lineup change to reverse out excess cement and cementing in the running tools... not nice!).
  • Also need to consider the type of liner hanger being used... with some of the new expandable liner hangers you cannot prove the running tools are free before committing to the cement job and planning to reverse excess cement can negate (or at least confuse) the fallback plan of circulating all the cement out of hole if the expandable hanger fails to set.
Hope it helps

Graham
PaulHowlett
CEO
Sudelac
Total Posts: 81
Join Date: 10/04/08

Circulating excess cement off the top of a liner hanger system can be one of the trickier parts of liner hanger installation and several things need to be considered. I shall not try to address them all but provide this as food for thought and perhaps it will stimulate discussion.

First and foremost, consider carefully your cementing volume and the amount of cement that could be above the top of the liner, in length terms and volume, also how you will handle it at surface.

Do your cement calcs :

  • Consider what if any excess you will pump and what the impact of this will be - if you don´t lose any cement what the height of the plug above the liner will be with the deployment drill pipe in.
  • Consider the ECD pressure that this volume will be once it is all in the drill pipe with any weighted spacer that was ahead of it, this pressure can sometimes be quite a surprise. 
  • Consider what pump rate you can achieve with this ECD and still handle it at surface when the cement arrives
  • Consider the time it will take, including picking up the running tools, getting them to the top of the liner, closing the BOP´s etc, lining up, making sure the cement head can go this high with the hoses etc, all as part of your slurry thickening schedule, add it to the placement time and make sure you allow a safe total job time from start to finish.
If you are using an integral liner top packer you are probably using a retrieve-able pack-off and tail-pipe for the liner wiper plug/s :
  • Make sure you can pull this all the way up, they are often telescopic and take more distance to get to the liner top than you think. Normally the integral liner top packer is set with the packer setting tool before the pack-off is pulled, which avoids u-tubing.
Consider not reversing out the cement, based on your prior shoe and its leak-off and the ECD calculated for reversing out, if you do not see any clear indication of the packer setting, as you could squeeze the cement down the liner top whilst reversing.

One thing to consider is pulling the pack-off, but leaving the tail-pipe inside the liner top, then pumping +/-25bbls the long way to move the cement above the liner top by say 200ft or so, then pulling the tailpipe above the liner top before you start reversing. This serves several purposes :
  • It proves the slurry is move-able, you might get an indication of the volume above the liner top due to the differential pressure to move it slowly
  • It also helps to avoid cement being reversed into the liner top which later can confuse when you enter it with the clean-up string.
I would only reverse out cement if you bump the plug and it holds pressure and you check your floats and they are holding back-pressure.

Also have a contingency to pull above the planned top of cement and circulate out the long way, being sure you can handle any cement that does come back, if it does. Be sure to jet and flush the area below and through the BOP´s when you get out of the hole.

I would have a thorough rig-site pre-planning meeting to agree all of the above and be sure the decision sequence is agreed between all parties before you start the job. My experience having run many liners (in a former life) is that focus and attention lapses once the liner is at TD, the hanger is set and the cement job finishes; and as those experienced know the liner hanger job is possibly entering its most critical phases, getting the running tools out, not dragging the liner up the hole, getting the packer set and dealing with excess cement.

I also advise checking the running tools carefully when they are out of the hole as often indications of success or failure are observed from shear screw remnants, pack-off seals, dogs on packer setting tools etc, cement residue and the like.

Finally when you are well above the liner, after circulating out the cement, prior to pulling out anymore consider pumping down a solid rubber flexible ball to clean the ID of the drill pipe.

Hope the above helps your planning considerations.
miaody
drilling supervisor
China National Offshore Oil Corporation
Total Posts: 2
Join Date: 24/09/09
Normally, we circulate in conventional way,there was no cement left at the top of liner.But if we reverse circulating, the cement left at the top of liner, so another trip to drill the cement plug was needed.
Sergei
Head of Completion and Well Interventions
Perenco - Oil and Gas
Total Posts: 4
Join Date: 31/01/12
Dave,
as you already stated, reversing the excess of your cement is quicker, and is considered as standard in many companies. You can control ECD by reducing the pump rate, thus basing your calculations on upward velocity needed for effective removal of the cement.
So, why don't you reverse out first, and only then perform the test on your liner hanger?
MikeSchneider
Drilling & Completions Specialist
Global Well Engineering Ltd
Total Posts: 14
Join Date: 17/07/12
Dave,
One DSV I have worked with for a long time prefers conventional circulation because of lower incidence of cement remaining on the internal upsets of the tool joints, which caused us worse problems than any film of cement on the casing. Another DSV prefers conventional circulation in cases where any gas may be circulated out during cementing, because of the risk of it howling up the drill pipe. Speaking for land operations, cement in the BOP has never been a problem for us.
What is the suggested mechanism for inducing a flash set solely due to reversing out? Over-shearing of small volumes of batch-mixed slurry has caused a dramatic drop in thickening time on liner jobs in past years, but not related to the reversing out.
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Dave Taylor - SPREAD Moderator

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Relentless Pursuit Of Perfection Ltd.

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