2. Basic Calculations

Table of Content

1. Volumes and Strokes
2. Slug Calculations
3. Accumulator Capacity — Usable Volume Per Bottle
4. Bulk Density of Cuttings (Using Mud Balance)
5. Drill String Design (Limitations)
6. Ton-Mile (TM) Calculations
7. Cementing Calculations
8. Weighted Cement Calculations
9. Calculations for the Number of Sacks of Cement Required
10. Calculations for the Number of Feet to Be Cemented
11. Setting a Balanced Cement Plug
12. Differential Hydrostatic Pressure Between Cement in the Annulus and Mud Inside the Casing
13. Hydraulicing Casing
14. Depth of a Washout
15. Lost Returns — Loss of Overbalance
16. Stuck Pipe Calculations
17. Calculations Required for Spotting Pills
18. Pressure Required to Break Circulation

2.8 Weighted Cement Calculations

Amount of high density additive required per sack of cement to achieve a required cement slurry density

$x=\frac{(\mathrm{Wt}\times 11.207983÷\mathrm{SGc})+(\mathrm{Wt}\times \mathrm{CW})-94-(8.33\times \mathrm{CW})}{(1+(\mathrm{AW}÷100\left)\right)-(\mathrm{Wt}÷(\mathrm{SGa}\times 8.33\left)\right)-(\mathrm{Wt}+(\mathrm{AW}÷100\left)\right)}$

where x = additive required, pounds per sack of cement
Wt = required slurry density, lb/gal
SGc = specific gravity of cement
CW = water requirement of cement
AW = water requirement of additive
SGa = specific gravity of additive

Example: Determine how much hematite, lb/sk of cement, would be required to increase the density of Class H cement to 17.5 lb/gal:
Water requirement of cement = 4.3 gal/sk
Water requirement of additive (hematite) = 0.34 gal/sk
Specific gravity of cement = 3.14
Specific gravity of additive (hematite) = 5.02

Solution:
$x=\frac{(17.5\times 11.207983÷3.14)+(17.5\times 4.3)-94-(8.33\times 4.3)}{(1+(0.34÷100\left)\right)-(17.5÷(5.02\times 8.33\left)\right)-(17.5+(0.34÷100\left)\right)}$
$x=\frac{62.4649+75.25-94-35.819}{1.0034-0.418494-0.0595}$
$x=\frac{7.8959}{0.525406}$
$x=\mathrm{15.1\; lb\; of\; hematite\; per\; sk\; of\; cement\; used}$

⬆ Table of Content