Cement Slurry Design For Oil And Gas Well Cementation

Presentation By: Himanshu Rajawat

Petroleum EngineeringFinal Year

Submitted To:Department of Petroleum EngineeringUniversity College of Engineering,Rajasthan Technical University,Kota (Raj.)

Objectives Of Cementing Provide zonal isolation. Support axial load of casing string. Provide casing protection against corrosive fluids. Support the wellbore. Protect water zones . To keep the wellbore intact.

Cement Slurry Design Factors influencing slurry design

1. Well depth, diameter & casing size.2. Bottom Hole Circulating Temperature (BHCT)3. Bottom Hole Static Temperature (BHST)4. Bottom Hole Pressure (BHP)5. Sample of cement, cement additive, mixing

water.

slurry design is carried out under well simulated conditions with cementing materials to be used at site.

Cement Slurry Parameters.

Slurry Density Thickening Time Rheology Fluid Loss Control Free Water Content Compressive Strength

All these parameter should be taken care to maintain well security & integrity.

Cement Additives At present the cement classes G and H can be modified easily

through the use of additives to meet almost any job specifications economically.

Types of cement additives:

Accelerators Retarders Extenders Dispersant Fluid loss additives Anti-gas migration additives

Accelerators Used for shortening the Thickening Time Used for shallow, low temp. & pressure well.Commonly applied accelerators are:• Sodium Chloride• Calcium Chloride• Potassium Chloride• Sodium Silicate• Sea Water for mixing

Retarders• Retarders delay the hydration of cement to

provide sufficient time to pump slurry in the well.• Increase thickening time but also delay strength

development.

• Needed whenLong pumping times are requiredTemperatures are high.

Brand Name

Manufacturer Effective Temp. Range

Property

HR-4 Halliburton Up to 76 ºC Solid brown powder -Calcium Lignosulphonate derived from

wood.HR-5 Halliburton 52 ºC to 97 ºC Black, solid powder -chemically

modified lignosulphonate.

HR-12 Halliburton 104ºC to 171ºC

Yellowish-brown powder -is a mixture of HR-4 retarder and an

organic acid.D-800 Dowell 52 ºC to 121

ºCDark brown powder -

Lignosulphonate retarder with reduced tendency for gelation.

D-150 Dowell 104 ºC -149 ºC

Dark Brown liquid

R-8 B.J.Services 93ºC to 204ºC Brown Powder

R-3 B.J.Services Up to 115ºC Light brown powder, lignosulphonate derived from

the wood pulp.

Dispersants• Also called friction reducers, these

materials make cement slurries easier to mix and pump by making them less viscous.

• Act on surface charges of the cement grains.

• Secondary retardation • Enhances fluid loss control.

Brand Name

Manufacturer

Effective Temp. Range

Property

CFR-3 Halliburton ----- Red-brown solid.

DO-65 Dowell Up to 121 ºC Light brown powder.

D-145A Dowell Up to 85 ºC Colorless, Viscous liquid low temp. dispersant

CD-31& CD-32

B.J.Services

4ºC to 204ºC Light brown Water soluble polymer powder.

CD-33 B.J.Services

4ºC to 204ºC Red-Water soluble polymer powder.

Fluid Loss Additives• Reduces the rate at which filtrate is lost to a

permeable formation. • Works by viscosifying the mix water or by

plugging the pore throat in the filtrate cake with long polymer chains.

• Examples: • Organic polymers (Cellulose) – CMHEC, HEC• Bentonite• Polyallylamine

Brand Name

Manufacturer

Effective Temp. Range

Property

Halad-9 Halliburton 15.5 ºC to 149ºC

Solid Powder- Additive is a blend of a cellulose derivative and a dispersant.

Halad-447 Halliburton ---- Solid, white powder -additive containing polyvinyl alcohol.should not be used with borax or boric acid.

Halad-413 Halliburton Up to 204º C Solid, brown/black powder

D-167 Dowell 10ºC to 260ºC

White Solid Powder- universal & cost-effective solution for fluid-loss control for all cementing application.

DO-60 Dowell Up to 120 ºC Blend of medium molecular weight polymers

FL-19 B.J.Services Up to 93ºC Water soluble high molecular weight polymers.

Gas Migration Control Additive

• Gas migration control additives are used to reduce the risk of gas invading the cement and migrating into the wellbore.

• Commonly used agents: D-600 G D-700 G FLAG-56 BA-10S BA-58L

Extenders• Additives that reduce slurry density and

increase slurry yield are called extenders. – Most allow the addition of extra water to slurry• Cement may be lightened to protect weak

formations or slurry yield may be increased to reduce cost.

Examples: Bentonite, Sodium silicate , Pozzolans

( Diatomaceous earth, Fly ash, Fume silica )

Heavy Weight Additives• These are required to counter high formation

pressures. • Common high density materials are:- Haematite:• Form : Red powder• Specific Gravity:-4.7-5.25 (g/cm3)• An iron ore (Fe2O3),chemically inert and requires

little additional water. Barite• Form:-White powder• Specific Gravity:-4.230 (g/cm3) Barite is a barium sulfate material used to weight drilling mud and cement slurries.

ONGC’S Specification of Class-G Cement(HSR) As per API

Physical Requirements

1. Water required for making slurry (% BWOC) 44.0

2. Free water content, % by volume 1.4 (max.)

3. Compressive strength after 8 hrsi) At 38⁰C, 1 atm.ii) At 60⁰C, 1 atm.

300 psi (min.)1500 psi (min.)

4. Consistency at 52⁰C & 1 atm., after 15-30 minute stirring 20 BC ( max .)

5. Thickening time ( in minute) at 52⁰C & 5160 psi 90 ( min. )120 ( max.)

Equipments in the lab Mud Balance : Warring Blender HT-HP Consistometer Atmospheric Consistometer  Fluid Loss Apparatus Viscometer Pressurized Curing Chamber Compressive Strength Testing Machine

MUD BALANCE

To minimize the danger of fracturing the formation, lost circulation or kicks. Cement slurry density should be more than or same as the drilling fluid density at cementing operation.

Fig: Mud Balance

It is operated according to the API Specifications.The mixer is operated at 4000 RPM for 15 sec., during which all the cement should be added to mix water and then at 12500 RPM for 35 sec.

CONSTANT SPEED MIXER

HP-HT CONSISTOMETERHP-HT Consistometer is used to determined the Thickening Time, the length of time which cements slurry remains in a pumpable fluid state under simulated wellbore conditions of temperature and pressure

ATMOSPHERIC CONSISTOMETER

It is used to conditioning of slurry for testing of rheological properties, fluid loss and various other properties. It works on Atmospheric Pressure.

VISCOMETERThe viscometer measures viscosity by applying a known shear rate on the cement slurry within the annular space b/w the outside sleeve or rotor and the bob.

FILTER PRESSAfter conditioning the slurry in atmospheric

consistometer, Here it is pressurised up to 1000psi. The loss of fluid is calculated.

HP-HT PRESSURIZED CURING CHAMBER

• It is a tool for compressive strength testing. It is designed to cure cement cube sample for compressive strength testing.

COMPRESSIVE STRENGTH MACHINE

It is used for the testing of the compressive strength of the cement. Cement cubes from the curing chamber are used for this purpose.

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