**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) |
---|---|

0.00 | |

0.00 | |

0.00 | |

0.00 | |

0.00 | |

0.00 | |

0.00 | |

Total String Lenght (Check) | 0.00 |

Length of Cement Plug after POOH | |

Total Volume of spacer (bbl) | |

Volume of Spacer ahead (bbl) | 0.00 |

Under-displacement (bbl) | |

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 |

DP Volume | 0.00 |

Annular Volume | 0.00 |

Wellbore Volume with DP in | 0.00 |

Wellbore Volume | 0.00 |

Metal Displacement | 0.00 |

Top (m) | Bottom (m) | ID (in) | OD (in) | Cap (bbl/ft) | Cap (bbl/m) | Volume (bbl) |
---|---|---|---|---|---|---|

0.00 | 0.00 | 0.00 | 0.00 | 0.00 | ||

0.00 | 0.00 | 0.00 | 0.00 | |||

0.00 | 0.00 | 0.00 | 0.00 | |||

0.00 | 0.00 | 0.00 | 0.00 | |||

0.00 | 0.00 | 0.00 | 0.00 | |||

0.00 | 0.00 | 0.00 | 0.00 | |||

0.00 | 0.00 | 0.00 |

DP/Hole Details | Top (m) | Bottom (m) | Hole/Casing Dia/ID (in) | Cap (bbl/ft) | Cap (bbl/m) | Volume (bbl) |
---|---|---|---|---|---|---|

0.00 | 0.00 | 0.00 | 0.00 | 0.00 | ||

0.00 | 0.00 | 0.00 | 0.00 | 0.00 | ||

0.00 | 0.00 | 0.00 | 0.00 | 0.00 | ||

0.00 | 0.00 | 0.00 | 0.00 | 0.00 | ||

0.00 | 0.00 | 0.00 | 0.00 | 0.00 | ||

0.00 | 0.00 | 0.00 | 0.00 | 0.00 | ||

0.00 | 0.00 | 0.00 | 0.00 | 0.00 |

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 | |||

Underdisplacement | 0.00 | 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) |
---|---|---|---|

Mud | 0.00 | 0.00 | 0.00 |

Spacer Ahead | 0.00 | 0.00 | 0.00 |

Cement Slurry (Annular) | 0.00 | 0.00 | 0.00 |

Cement Slurry (DP) | 0.00 | 0.00 | 0.00 |

Spacer Behind | 0.00 | 0.00 | 0.00 |

Mud | 0.00 | 0.00 | 0.00 |

Instructions:

a) Use the 7 sections to input different placement string diameter and/or different wellbore diameter (casing IDs, OH diameter). For **DP Details**then is **DP/hole Details**

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 onation to get the Excel version of this Balanced Plug Calculator with graphic output**

Recommended posts:

https://better-cementing-for-all.org/some-guidelines-for-cement-plugs

https://better-cementing-for-all.org/balance-to-succeed-a-case-of-cement-plugs-in-losses-situation

https://better-cementing-for-all.org/highly-deviated-and-horizontal-well-section-abandonment

Cheers

L. Diaz

Raul says

Great article exactly what I learn in schlumberger and Halliburton and Put in práctic for each cement plug that I pump.

Lenin Diaz says

Thanks for your contribution Raul

Cheers

L. Diaz

Robert Broussard says

I would like to try out your excel sheet if you would like to send it to me. Thanks

Lenin Diaz says

Hi Robert

Soon to be posted available to all

Cheers

L. Diaz

Karol says

Hi Leni,

This looks amazing. I have made my donation to get the excel file. what payment details do you need?

Lenin Diaz says

Thanks for your donation, I hope you enjoy the Excel sheet. BTW, I have a new version, able to use common oilfield units.

Cheers,

L. Diaz

Bobby Lewis says

Looks great.

I think I could do it on paper quicker than filling in the blanks.

H over c plus t

Lenin Diaz says

Sure you can Bobby,

Thanks for your input

Cheers

L. Diaz

John North says

During a complex multi-diameter hole, casing, rat hole, milled section and open hole with xs, cement plug job I came up with an idea to double-check the relatively complex calculations using a far simpler method. The sg of the steels we use is approximately 64.4 lb/gal (7.85 s.g.). If we know the combined weight of pipe inc. stinger for the length of the plug with the drill pipe out we can work out the displacement of the pipe from its weight lb/ft x ft (for each pipe section). Thus we can calculate the volume of cement displaced by the volume of steel pipe. That volume in a balanced plug will increase the height of the cement by the volume of the steel (gal) / (ann vol gal/ft+ id vol pipe gal/ft) in that section. If the same od/id stinger covers all the cement the additional volume is the displacement of the pipe. Then use the normal method to work out the increase of the height of the cement due to the pipe displacement. This saves calculating volumes for each section of the hole with different id’s with drill pipe in. Hope that I have explained this well.

Lenin Diaz says

Hi John, thanks for your contribution and I have to say that is clever indeed, plus very well explained for our readers.

In a way I used a similar approach with several conditional equations for variations of wellbore / Pipe OD with and without the pipe in. You can have a look at the Excel version of the calculator.

Cheers

L. Diaz

HERVE NDAYE says

thank you

HERVE NDAYE says

i’m really interested in your article

i’m working my thesis on the platform design and cementing design.

i have a preocupation for you, my adresse is ingenieur.ndaye@gmail.com

Lenin Diaz says

Hi Herve, Happy to help. Please let me know more details

mustafa says

Hello How Can I get the Excel copy of the above sheet please ?

Lenin Diaz says

Hi Mustafa, thanks for your interest in my blog in well cementing. I am sharing the Excel sheet version of the calculator via email following your kind donation to my website.

Cheers

L. Diaz

montader says

hello Mr. Lenin ,

i would love to know your judgement about the right position for OEDP while pumping a cement plug , which is more preferable for you to position the stirng across the loss zone or above it by some distance ?

i would like to know any means to message you if you do not mind please .

Lenin Diaz says

Hi Montader, thanks for your question.

In the case of total losses to a well-identified narrow (induced or natural fractures, faults, or similar) losses zone it is best to position the end of the DP above and the distance would depend on the severity and nature of the solution. Typically if your solution is something reacting in-situ you would increase the separation from the top of the losses zone; other than that (particle-based or LCM combination) you can place it right above. Another point of view to place the DP’s end above the losses zone is when having the solution circulating is considered counterproductive or catastrophic in nature (like a Calcium Chloride + Sodium silicate solution).

For partial losses, you can place the DP at the bottom of the losses zone, particularly for longer intervals, like a high-permeability layer.

You can use my personal email: dlenin@hotmail.com

Cheers,

L.Diaz

montader says

i would like also to know your thoughts on the perfect string position to spot and squeeze whether Coss_linking polymer pills or any other LCM pills for thief zone ? should it be on bottom (vugs, fractures on bottom and let’s say the string is a meter off bottom) then POOH to the top of LCM pill and squeeze it ?or to Place the string above loss zone some distance (10_30)m then spot the pill and squeeze it ? .

in the fields we tend to go with the second option which is to spot the pill above the loss zone and squeeze once left the bit . iwe had an argument about this matter some assumed if the string positioned above the top of loss zone , there is a possibility that part of pill would travel up the annulus instead of moving down to the loss zone therefore other pill could be required .

i wish that you could address this issue in some details and i will be patiently waiting for any words .

regards

Lenin Diaz says

Hi Montander,

As I previously mentioned, the position of the string depends on the severity of the losses (total or partial), and if you like the risks associated with the solution itself.

In the case of total losses, solution-fluids would flow to the path of least resistance and into the losses zone.

However, at some point, the fluid level can move up the annulus (due to the characteristics/volume of the solution fluids increasing the friction pressure at the losses zone), including the possibility of solution fluids moving behind the placement string. This possibility shall be risk-assessed and proper prevention and mitigation included in the design and placement procedure.

Some of these measures possibly including; the distance between the DP and the top of the losses zone, volume of fluids, modifying characteristics of the fluids (thickening or gelling time), use of pre and post-flushes, reciprocation of the DP, use of disposable tail-pipe, etc.

In any case, it is imperative to monitor the annulus for any returns during the treatment and be ready to close if required to ensure injection.

Hope this helps,

Cheers,

L. Diaz

montader says

many thanks sir for your time to reply my question i highly appreciate that

Lenin Diaz says

Thanks to you Montader, for supporting my website

sadeghi says

very helpful

Lenin Diaz says

Thanks Sadeghi. Any way I can help, let me know