Free Balanced Plug Calculator at the end of this post. Check it out !
The most common placement method is the balanced plug technique. The work-string is run into the wellbore to the desired depth for the plug base. Contamination or mixing with the control fluid is avoided by the use of appropriate volumes of spacer or chemical wash. These are pumped ahead of and behind the cement slurry and the volumes correspond to the same heights in the annulus and in the pipe.
Volumetric calculations to place a balanced cement plug can be easily done based on the well schematic, pipe’s dimensions, open hole and casing sizes and the final cement plug length. See next images for an example calculation.
It is common practice to slightly under-displace the plug (usually by 1–3 bbl). This practice avoids control fluid flow back on the rig floor after placement and allows the plug to reach a hydrostatic balance. Once the plug is balanced, the pipe is slowly pulled out of the cement to a depth above the plug, and excess cement is reversed out.
The maximum “recommended” cement plug length that can be placed in a single attempt is 200 meters.
In all my years, I never came across a good excel sheet for a quick calculation of balanced cement plugs, they were always very specific or unable to consider variations in wellbore and drill pipe diameters. Well, I have finally completed one excel sheet that I believe can be helpful. Now, I am saying this because I did this excel sheet and it is working great for me, but I am sharing it with the objective to help people. I would like you to try it and give me your opinion or what improvements or changes it needs.
Finally, please remember it is a good practice to always double-check all job-related calculations, volumes, etc., with a team member, service company (
Balanced Plug Calculator (Donate to get the Excel Sheet)
|DP Details||Lenght (m)|
|Total String Lenght (Check)||0.00|
|Length of Cement Plug after POOH|
|Total Volume of spacer (bbl)|
|Volume of Spacer ahead (bbl)||0.00|
|TOC after POOH DP||0.00|
|Bottom of Plug||0.00|
|Cement Slurry Volume (bbl)||0.00|
|Average Cement Plug / wellbore Size (in)||0.00|
|Average Capacity (bbl/ft)||0.00|
|Average Capacity (bbl/m)||0.00|
|Wellbore Volume with DP in||0.00|
|Top (m)||Bottom (m)||ID (in)||OD (in)||Cap (bbl/ft)||Cap (bbl/m)||Volume (bbl)|
|DP/Hole Details||Top (m)||Bottom (m)||Hole/Casing Dia/ID (in)||Cap (bbl/ft)||Cap (bbl/m)||Volume (bbl)|
|Output Details||Lenght (m)||Top (m)||Vol in DP (bbl)||Vol in Annulus (bbl)|
|TOC with DP in||0.00|
|Length of Cement Plug with DP in||0.00||0.00||0.00|
|Displacement to Balance||0.00|
|Volume of Cement inside with underdisplacement||0.00||0.00|
|TOC in DP with DP in and Underdisplacement||0.00|
|TOC in Annulus with DP in and Underdisplacement||0.00|
|Total Volume of Spacer||0.00|
|TOS after POOH||0.00|
|Length of Spacer after POOH||0.00|
|TOS with DP in||0.00|
|Volume of Spacer behind||0.00||0.00|
|Volume of Spacer Ahead||0.00|
|TOS in DP with DP in and Underdisplacement||0.00|
|TOS in Annulus with DP in and Underdisplacement||0.00|
|Summary Results||Volume (bbl)||Length (m)||Top (m)|
|Cement Slurry (Annular)||0.00||0.00||0.00|
|Cement Slurry (DP)||0.00||0.00||0.00|
a) Use the 7 sections to input different placement string diameter and/or different wellbore diameter (casing IDs, OH diameter). For
b) Total volume of spacer (bbl) is the sum of spacer ahead and spacer behind. Change the total value until getting a round number for the volume ahead.
Please make a D