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CLIP Incident due to low ID Stinger
08 January 2020
Dear All,

We wanted to place a cement plug in a 7" liner (5.92 ID) , with a cement string.

  • 3-1/2" Stinger would result in a higher length of plug (<200 m) due to low annular clearance
  • 2-3/8" would result in a lesser plug length but has lower ID (~1.5 in)
One of my colleagues said that 2-3/8" pipes could result in a CLIP (Cement Left in Pipe) Incident, but since we don't have any mechanical barrier or obstruction through which there can be a possibility of fluid bypassing and the solids forming a plug, there seems very low possibility of such incident.

Has anyone of you experienced any CLIP Incident where the pipes were cemented due to lower ID of stinger and had no mechanical barriers separating the different fluids i.e. mud, cement and spacer.

4 answer(s)
D&C Project Coordinator / Decommissioning
SPREAD Associates
Total Posts: 35
Join Date: 25/01/16
Two things to consider.  One is if the hole with casing spiraled then to get a good displacement be equipped to rotate the string as you displace the cement for a balanced plug.   Two is the balancing the plug so the top of cement is at desired height.   As cement falls out of cementing stinger it can maintain the height of the top of plug as stinger is removed.   Once above the desired top of cement can reverse out volume of cementing string but be sure there is sufficient barrier to hold back pressure.  This can give a clean top of cement.  Would suggest a stinger length of 2 7/8" although the 3 1/2" can work but need to use lower running and pulling speeds.  Sounds like you need someone with experience from the contractor.  Balancing the plug should end with cement at same height no matter what tubing size used.
Production Chemistry Well Fluids Team Lead
Total Posts: 2
Join Date: 02/12/14

Umair, I have experience of a CLIP event a number of years back when placing a cement plug through a 3-1/2in kill string.  Despite an extensive post mortem investigation we never identified the root cause, however we did identify some additional risks associated with placing cement through extended lengths of small ID pipe and some learnings which were applied to subsequent successful jobs.

  • Risk of debris plugging the string.  Learning was to ensure the string is drifted and we started pumping a foam wiper ball during pre-job circulation to verify the string was clear ahead of cementing.

  • Assess shear sensitivity of cement slurry.  In a similar way as done for coiled tubing cement jobs consider additional sensitivity testing of the cement slurry to confirm it is not sensitivity the higher shear energy it will see in the small ID pipe.



Senior Drilling Engineer
Pakistan Petroleum Ltd
Total Posts: 30
Join Date: 02/08/15

Our first priority was 2-7/8" string, but since that was not available with rig contractor, hence we looked at 2-3/8" as an option.

This plug will be required to isolate the fish below and no side track would be performed through it , so it does not need very high CS
Managing Director (
Relentless Pursuit Of Perfection Ltd.
Total Posts: 468
Join Date: 10/01/05
Hi Umair

I recommend that you look into Sudelac's Perfect Plug Placement  system and/or their Hydraulic Disconnection Tool (

There are other similar systems on the market, but Sudelac would seem to have been the pioneers!

To answer your question:
1.  I have seen the centre of a cement plug sucked out the centre by too small an ID. (2⅜")
2.  Have you thought about 2⅞" string as a compromise, with flush  couplings?

You also need to think about what is the 'base' that you will be setting the plug on.  If you don't have a mechanical plug or solid base (previous cement plug), then consider a CST (Cement Support Tool, an inverted umbrella) or VRP (Viscous Reactive Pill).

Also, a decision might be based on how critical it is to have a hard TOC when you go in to tag, and what is the purpose of the cement plug.
  • Is it going to be used to kick-off later?
  • Does it need got be a minimum length (Govt regulations, Company Rules)?
  • Will it need to be dressed off and weight-tested?
  • How long before you need top tag/test the plug (gives you options on retarders).
I hope this helps.



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