1. Chapter V
Primary Cementing

2. Two plug method:
Cementing head
Bottom plug – hollow
Top Plug - solid

3. Portland cement powder
&
Water
Slurry =
Also called Neat cement
Shallow well hrs WOC
WOC = Waiting on Cement

4. Type C Cement
Portland – is a finer grind
Avg. diameter is smaller.
Reduces WOC ~ 1/2

5. By 1968
Class A – Neat Cement
B - Sulfate resistant
C - Shorter WOC
D – 10,000 ft
E - 10,000 – 14,000 ft
F - 10,000 – 14,000 ft with good sulfate resistance

6. Basic Cement ft
Class G
Good sulfate resistance
Class H ft
Moderate sulfate resistance
Being phased out

7. Accelerators - CaCl2
NaCl

8. Retarders
Calcium Lignosulfonate

9. Lightweight additives
Most cement slurries lbs/gal
Drilling mud 9.5 lb/gal lb/gal
Hydrostatic head (HH) at 4000 ft
HH (mud) = 9.5 x = psi/ft
0.494 psi/ft x 4000 ft = 1,976 psi
HH (cement) = 15.6 x = psi/ft
psi/ft x 4000 ft = 3,245 psi

10. Heavyweight Additives
( lb/gal)
Hematite (iron ore)
Barite
Lost circulation additives
Gilsonite
Cellophane flakes
Walnut Hulls

11. Salt additives - NaCl Optimum typically 18% salt
1.) Improve bonding in shale
2.) Dispersing agent
3.) Causes cement to expand as it sets
Optimum typically 18% salt

12. Slurry Design
Pumpable until your finished
P & T both increase with depth
P ~ psi/ft T ~ 2 °F/ft
Depth (ft) Temp (°F) 5,
10,

13. Viscosity Type G = 5 gal water/sack TOO viscous to pump Optimum:
Maximum strength at 2.8 gal water/sack
TOO viscous to pump
Optimum:
Type G
= 5 gal water/sack

14. Strength
- Composition
- Age (28 days)
- Temp > 230 F reduces strength

15. WOC determined by time to reach 80 -100 psi tensile
Strength = adequate →
8-10 psi tensile strength
Compressive ~
8 - 10x tensile
WOC determined by time to reach psi tensile

16. Volume & Density (MATH!)
Cement measured in "sacks"
1 sack = 94 lb
= 1 cu ft dry powder
1 cu ft cement = cement void space

17. Slurry yield - cu ft/sack
Slurry weight - lb/gal
Slurry yield - cu ft/sack
Example - Class G
Absolute volume of water = 8.33 lb/gal
Water = 0.12 gal/lb
Cement = gal/lb

18. Volume per sack for Class G
Water = 0.12 gal/lb
Cement = gal/lb
Volume per sack for Class G
94 lb x gal/lb = 3.59 gal/sack
Volume of cement gal/sack
Volume of water gal
Total volume slurry = gal

19. Slurry yield =? Slurry density = 135.65 lb = 15.8 lb/gal 8.59 gal
Weight of water = 5 gal x 8.33 lb/gal
= lb
Slurry lb 8.59 gal
Cement 94 lb 3.59 gal
Water lb 5 gal
Slurry density = lb = lb/gal
8.59 gal
Slurry yield =?

20. Conversion factor: cu ft → gal
7.48 gal/cu ft
Slurry yield:
8.59 gal/sack
= 1.15 cu ft/sack
7.48 gal/cu ft

21. 7” 8.75” Class G = 8.59 gal/sack Hole = 8.75" diameter OD casing = 7"
Area=
OD casing = 7"
1500 ft deep
Area=
8.75” 7”
Area=
Area=
Area= sq. in.
Area= 0.15 sq ft

22. amount of 225.5 cu ft slurry needed = 1.15 cu ft / sack = 196 sacks
Volume = 0.15 sq ft x 1500 ft = 225 cu ft
amount of
slurry needed
225.5 cu ft
1.15 cu ft / sack =
= 196 sacks

23. Safety factor Engineering Margin Surface casing - 100% (400 sacks)
Intermediate casing %
Production casing - 25%
Can't run out !

24. Placement Techniques Mud & cement are: Non-Newtonian fluids
laminar flow

25. Non-Newtonian
laminar flow
"gel"
critical velocity
bonding of casing

26. Solutions: Achieve bonding
1.) Clean casing
2.) Condition the mud.
3.) Pre-flush
4) Use centralizers
5.) Use scratchers
6.) Flow rate high enough for turbulent flow
7.) Sufficient contact time
turbulent flow

27. 260 linear ft/min "rule of thumb"
0.15 cu ft / ft
× 260 ft/min
39 cu ft/min = sacks/min
1.1 cu ft / sack
39 cu ft/min x 7.48 gal / cu ft = GPM