As regular readers are aware, I encourage the asking of cementing problems so that I can publish them. If one person has a question, the chances are that others do too, and we can share the knowledge.
An inbound question from a reader
Below is a summary of an answer recently given in response to a general request about tie-back casing cementing.
Sometimes I receive questions related to a specific job, and the discussion can’t get published online. The content of this page is about a non-confidential question topic.
I have categorised this post as remedial cementing according to the original request. However, we should note that tie-back cementing can be initially defined as an extension of a casing during well construction, i.e., primary cementing.
Please feel free to provide your comments or more information about tie-back casing cementing.
Summary:
Tie-back casing and cementing is a remedial technique with the intention to cover a damaged intermediate casing above the top of an existing production liner. The cementing procedure follows the same principles and methods of primary cementing.
Tie-back cementing under such conditions involves important differences and additional risks.
- The use of washes and spacers ahead of cement slurries will prevent cement contamination and mixing with the fluid in the hole. (Important due to the potential incompatibility with the completion fluid or brine).
- The condition of the outer-casing should be appropriately accessed. The application of safety factors for the outer-casing burst pressure. TOC, cement density and rheology shall be selected accordingly to lower the maximum ECD.
- The dimensions and position of the tie-back tool (mule shoe) during cementing (accounting for casing elongation) shall be adequately understood and any restriction to flow shall be appropriately identified and considered in the cement job simulation.
- Plan for an adequate number of short joints of casing to prevent the cement head becoming too high above the rig floor.
- We should consider a cast iron bridge plug (CIBP). The ECD generated during the tie-back cementing operation could leak downwards and/or exceed formation pressure.
- The most important cement slurry properties are Free Water, Fluid Loss, Rheology, Gelling tendency, i.e., Cement Slurry Stability.
Need more information?
Feel free to comment below.
what range of fluid loss is ok for in example: 7″ tie back in 9 5/8″ csg? I asked this question because there is no formation as porous media to loss fluid into it.
thank you Mr. Diaz
In tie-back cementing, the cement slurry sometimes flows through narrow annular gaps and/or small clearance in the tie-back assembly. In this geometry, the pressure drop might be high enough to cause slurry filtration eventually impeding further cement displacement.
The fluid loss requirement has to be assessed taking into account the tool schematic/dimensions, position of the tool (mule shoe/openings/receptacle) during the job, elongation of the casing and volume of cement (the higher the cement volume the higher the risk, hence the lower the fluid loss requirement). However a value of 75 to 150 ml/30min should be acceptable.
thank you for your complete answer.
Thanks for your contribution
L. Diaz
Dear Mr. Diaz,
Would you plz send me some references that exactly mention acceptable fluid loss value in primary and remedial cementing.
Jahromi,
I will post acceptable values of API FL for primary and remedial cementing operations ASAP. However, in general the importance of FL control increases with depth, differential pressure and restrictions. FL values are also usually lower in Remedial than in primary cementing, but under certain conditions like HPHT, permeable formations layers, gas/fluids migration control or other; The FL values in primary cementing can be required to be as low as 30 ml/30min or less.
Finally, just to understand what is low and high in terms of FL, the FL values for a cement slurry go from 15 (very low control) to 1500 ml/30min (no control).
Thanks for your contribution
L. Diaz