Tag Archives: Drilling Fluids Formulas

Starting volume of original mud (weight up with Calcium Carbonate)

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You know how much volume will be increased due to adding calcium carbonate into the system; however, you sometimes are limited to total volume due to limit pit volume on the rig so you need to calculate starting volume to achieve the predetermined final volume of desired mud weight.
This formula below is used to determine the staring volume of mud (for calcium carbonate system).

Starting volume in bbl  = VF x (22.5 – W2) ÷ (22.5 – W1)

Note: 22.5 is density of calcium carbonate in ppg.

Where; W1 = current mud weight in ppg

W2 = new mud weight in ppg

VF = final volume of mud needed in bbl

Example: Determine the barrel of starting volume of 10.0 ppg (W1) mud required to achieve final volume of 100 bbl (VF) of 13.0 ppg (W2) mud with calcium carbonate:

Starting volume in bbl = VF x (22.5 – W2) ÷ (22.5 – W1)

Starting volume in bbl = 100 x (22.5 – 13.0) ÷ (22.5 – 10.0)

Starting volume = 76 bbl

In order to achieve  final mud volume of 100 bbl of 13.0 ppg mud weight up with calcium carbonate, you must have 76.0 bbl starting volume of 10.0 ppg mud.


Please find the Excel sheet for calculating Barrel of starting volume of original mud weight required to give a predetermined final volume of desired mud weight with CALCIUM CARBONATE.

Ref book: Formulas and Calculations for Drilling, Production and Workover, Second Edition

Increase Mud Weight by Adding Calcium Carbonate

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Carbonate is weighing agent mostly used in horizontal well because it does not plug up formation. We can use the same weight up concept with barite to calculate how to weight up with carbonate. Follow a topic below to learn how to weight up with calcium carbonate.

NOTE: The maximum practical mud weight attainable with calcium carbonate is 14.0 ppg.

 

This formula below is used for calculating how many sacks of calcium carbonate required per 100 bbl of drilling fluid (Mud weight increase with calcium carbonate (SG – 2.7))

Sacks of calcium carbonate per 100 bbl of mud = 945 x (W2 – W1) ÷ (22.5 – W2)

Where; W1 = current mud weight in ppg

W2 = new mud weight in ppg

Example: Determine the number of sacks of calcium carbonate per l00 bbl required to increase the density from 10.0 ppg (W1) to 13.0 ppg (W2):
Sacks of calcium carbonate per 100 bbl of mud = 945 x(13.0 – 10.0) ÷ (22.5 – 13.0)

Sacks of calcium carbonate per 100 bbl of mud = 298.4 sacks
If you have total volume of 500 bbl of mud, calcium carbonate required to increase mud weight from 10.0 ppg to 13.0 ppg is 1,492 sacks (298.4×500/100).

Please find the Excel sheet for calculating how many sacks of calcium carbonate required per 100 bbl of drilling fluid.

Ref book: Formulas and Calculations for Drilling, Production and Workover, Second Edition

Starting volume of original mud (weight up with Barite)

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You know how much volume will be increased due to adding barite into the system; however, you sometimes are limited to total volume due to limit pit volume on the rig so you need to calculate starting volume to achieve the predetermined final volume of desired mud weight. This formula below is used to determine the star volume of mud in case of weighting up with Barite.

Starting volume in bbl = VF x (35 – W2) ÷ (35 – W1)

Where; W1 = current mud weigth in ppg

W2 = new mud weight in ppg

VF = final volume in bbl

Example: Determine the starting volume (bbl) of 10.0 ppg (W1) mud required to achieve 100 bbl (VF) of 13.0 ppg (W2) mud with barite:

Starting volume in bbl = 100 x (35 – 13.0) ÷ (35 – 10.0)

Starting volume in bbl= 88.0 bbl

In order to achieve 100 bbl of 13.0 ppg mud weight up with barite, you must have 88.0 bbl starting volume of 10.0 ppg mud.

Please find the Excel sheet for calculating Barrel of starting volume of original mud weight required to give a predetermined final volume of desired mud weight with barite.

Ref book: Formulas and Calculations for Drilling, Production and Workover, Second Edition

Bulk Density of Cuttings Using Mud Balance

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Wet cutting coming over shale shakers can be used to determine cutting bulk density. This post demonstrates you how to find bulk density (specific gravity) in specific gravity of cutting using mud balance so please read and understand procedure to determine resulting weith with cutting plus water (RW) and then use RW to determine specific gravity of cutting bulk density.

Bulk Density of Cuttings by Using Mud Balance - (OilfieldPix.com, 2017)

Bulk Density of Cuttings by Using Mud Balance
– (OilfieldPix.com, 2017)

Procedure to obtain resulting weight with cuttings plus water (RW):

1. Cuttings must be washed free of mud. In oil base mud, diesel oil can be used instead of water.
2. Set mud balance at 8.33 ppg.
3. Fill the mud balance with cuttings until a balance is obtained with the lid in place.
4. Remove lid, fill cup with water (cuttings included), replace lid and dry outside of mud balance.
5. Move counterweight to obtain new balance. This value is “Rw” = resulting weight with cuttings plus water in ppg.

The specific gravity of cutting is calculated as follows:

SG = 1 ÷ (2 – (0.12 x Rw))

Where;
SG = specific gravity of cuttings – bulk density
Rw = resulting weight with cuttings plus water in ppg

Example:
Determine the bulk density of cuttings:
Rw = 14.0 ppg
SG= 1 ÷ (2 – (0.12 x 14.0))
SG = 3.13

Moreover, if you can to convert specific gravity to mud weight (ppg and lb/ft3) and pressure gradient (psi/ft). Learn more about how to Convert specific gravity to mud weight (ppg and lb/ft3) and pressure gradient (psi/ft)

Please the Excel sheet used to calculate Bulk Density of Cuttings Using Mud Balance

Ref books: Lapeyrouse, N.J., 2002. Formulas and calculations for drilling, production and workover, Boston: Gulf Professional publishing.

Bourgoyne, A.J.T., Chenevert , M.E. & Millheim, K.K., 1986. SPE Textbook Series, Volume 2: Applied Drilling Engineering, Society of Petroleum Engineers.

Mitchell, R.F., Miska, S. & Aadny, B.S., 2011. Fundamentals of drilling engineering, Richardson, TX: Society of Petroleum Engineers.