This document discusses cement classification, slurry design, and additives used in oil well cementing. It describes the four main components of Portland cement and their functions. It outlines the API classification system for oil well cements based on depth and characteristics. Key factors influencing cement slurry design are identified as well depth, temperature, and pressure. Important slurry parameters like density, thickening time, rheology, and fluid loss are discussed. Common additives used as accelerators, retarders, dispersants, and for fluid loss control are identified.

1. Classification of Cement;
Slurry Design & Additives
Chirag Vanecha
16BPE137
SPT, PDPU.
Faculty Mentor: Mr. Chandan Sahu

2. Well Cementing
• Well cementing is the process
of introducing cement to the
annular space between the
well-bore and casing or to the
annular space between two
successive casing strings.
• Cement Sheath??

3. Functions of Cement
 In an oil/ gas well, the primary functions of cement are:
• Provide zonal isolation
• Support axial load of casing strings
• Provide casing support and protection against corrosive fluids
• Support the borehole

4. Portland Cement components
• Tricalcium silicate(C3S)- Fastest hydration Overall and early strength
Protect sulphate attack. Average content 40% to 67%
• Dicalcium Silicate(C2S)- Very important in Final strength. Hydrates
slowly. Average content 25% to 35%
• Tricalcium Alluminate(C3A)- High early strength and initial set.
Readily gets attacked by sulphate water. Average content 3% to 15%.
• Tetracalcium aluminoferrite(C4AF)- Initial set and early strength.
Average content 10%.

5. API Classification of Oil-well Cement
CLASS Depth Range Characteristics
A Surface to 6000 ft • Ordinary cement (No special
properties)
• Similar to ASTM Type 1
B Surface to 6000 ft • Low C3A than Class A
• MSR to HSR
• Similar to ASTM Type 2
C Surface to 6000 ft • High Early Strength
• High C3S content & surface area
• Similar to ASTM Type 3
• LSR to HSR

6. API Classification of Oil-well Cement(ctd.)
CLASS Depth Range Characteristics
D 6000 ft to 10,000 ft • Used for Moderately high
temperatures& pressures conditions
• MSR & HSR
E 10.000 ft to 14,000 ft • Used for High temperatures&
pressures conditions
• MSR & HSR
F 10,000 ft to 16,000 ft • Used for Extremely high
temperatures& pressures
• MSR & HSR

7. API Classification of Oil-well Cement(ctd.)
CLASS Depth Range Characteristics
G& H • Basic cement from
surface to 8000 ft
• All depths
• Can cover wide range of depth and
temperature with accelerators and
retarders
• MSR& HSR
• No additions other than calcium
sulphate or water or both
J 12.000 ft to 16,000 ft • Can cover wide range of depth and
extremely high temperatures with
accelerators and retarders
• MSR& HSR
• No additions other than calcium
sulphate or water or both

8. Cement Slurry Design
 Factors influencing slurry design
• Well depth, diameter & casing size
• Bottom Hole Circulating Temperature
• Bottom Hole Static Temperature
• Bottom Hole Pressure

9. Cement Slurry Design (ctd.)
Cement Slurry parameters:
• Slurry density
• Thickening Time
• Rheology
• Fluid Loss Control
• Free Water content
• Compressive strength

10. Slurry Density
• Should be the same as mud to minimize the risk or blowouts or lost
circulation
• Measured using mud balance
• Low density are prepared with bentonite, pozzolan, gilsonite, perlite,
Diatomaceous earth
• Bentonite is used in concentration up to 35%, the reduction is due to
water added. more water requires for bentonite addition.
• Density increases by adding barite, iron ores or galena

11. Thickening time
• Determine the length of time the slurry can be pumped
• It is the time necessary for the slurry consistency to reach 100 poises
(70 poises is the maximum pumpable viscosity)
• Thickening time can be modified by Additives(accelerators/retarders)
• In practice the thickening time should be at least 25% higher than the
time necessary to accomplish the operation

12. Cement Additives
• Accelerators
• Retarders
• Dispersant-Also called friction reducers, these materials make cement
slurries easier to mix and pump by making them less viscous.
Enhances fluid loss control.
• Fluid Loss additives
• Anti-Gas migration additives-Gas migration control additives are used
to reduce the risk of gas invading the cement and migrating into the
wellbore.

13. Accelerators
• Are used to reduce the thickening time (minimizes the waiting period)
• Used for shallow wells and surface casings and low temperatures
zones
• Examples: Calcium Chloride
Sodium Chloride/Sea water for mixing
Potassium Chloride
Gypsum
Sodium silicate

14. Retarders
• Are used to increase the thickening time (waiting period is increased)
• Retarders are used for cementing deep and hot wells.
• Examples:
Calcium lignosulphonate (increases thickening time with low
concentrations)
Calcium lignosulphonate + organic acid (high temperature conditions)
Calcium-sodium lignosulphonate when bentonite is used in slurry
Sodium tetraborate (borax)
Carboxymethyl hydroxymethyl cellulose

15. Fluid Loss Control
• It is important to limit the loss of water filtrate from a slurry to a
permeable formation.
• Reasons:
Minimize hydration of water sensitive formations
Limit the increase in slurry viscosity
Allow for sufficient water to be available for cement hydration
• Examples of filtration control additives:
latex, organic polymers(cellulose), Polyallylamine