BY : MEHUL JAIN

3rd year B.Tech.

UCE,RTU,KOTA

1. CEMENTATION

2. TYPES OF CEMENTATION

3. CEMENT SLURRY DESIGN AND

TESTING

4. SUMMRY

> Oil well cementation is the

process of mixing of a slurry of

cement, cement additives and

water and displacing it down the

casing, tubing or drill pipe to a

pre specified point in the well.

Secure and Support the casing in the hole.

To restrict fluid movements between formations

(Zone Isolation).

Stop the movement of fluid into regular or

fractured formations ( lost circulation ).

To protect the casing from corrosion.

Withstand the shock of drilling & perforating.

To keep the wellbore intact.

PRIMARY CEMENTATION JOB• The cementing takes place soon after the lowering

of casing is called primary cementation.

Conductor

Surface

Intermediate/Isolation

Production

High Press Gas

Fresh Water

Gas

Oil

Water

Oil

Surface Casing

Intermediate Casing

Production Casing

Conductor Casing

PRIMARY CEMENTING

•SECONDARY CEMENTATION JOB

- Any cementing operation that occur

after the primary cementing operation.

•PLUG CEMENTING

•Abandoned, deviation, lost zone

•SQUEEZE CEMENTING

•Seal micro annulus, water shutoff

Cement slurry design.

Quality assurance of cement and cement

additives for procurement.

Evaluation & testing of oil well cement for

procurement.

To design & formulate suitable cement

slurries for better cement bond.

To provide the best & most suitable

cement slurry design & formulation in

minimum possible time

Manufacturing of Portland Cement

• Portland cement’s basic raw material: limestone

and clay.

• Oxides of Ca, Al, Fe, Si react at high temperatures

in the Kiln (1450– 1500 ⁰C ).

• When it cools, it becomes balls of cement clinker.

• After aging in the storage, the seasoned clinker is

taken to the grinding mills where gypsum is added

to (CaSO4.2H2O) to retard setting time and

increase ultimate strength.

Cement is thought to be made up of four crystalline

components in the clinker that hydrate to form a rigid

structure.

1. Tricalcium silicate (3

CaO.SiO2 or C3S)

2. Dicalcium silicate (2

CaO.SiO2 or C2S)3. Tricalcium Aluminate (3

CaO.Al2O3 or C3A)

4. Tetracalcium aluminoferrite

(4CaO.Al2O3.Fe2O3C4AF)

The reaction is exothermic and generates a

At present the cement classes G 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

Special materials:- Antifoam, silica, suspending,

weighting.

Accelerators

Used for shallow, low temp. & pressure

well.

Shortens setting time & promote early

strength development.

1. NaCl ( 3-10% BWOW )

2. CaCl2 ( 2-4% BWOC )

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 when

-Long pumping times are required.

-Temperatures are high.

Brand

Name

Manufacture

r

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

ºC

Dark brown powder -

Lignosulphonate retarder with

reduced tendency for gelation.

D-150 Dowell 104 ºC -149

ºC

Dark Brown liquid

R-8 B.J.Service

s

93ºC to 204ºC Brown Powder

R-3 B.J.Service

s

Up to 115ºC Light brown powder,

lignosulphonate derived from the

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.

Polyanions- polymelamine,

polynapthalene, polystyrene

sulpfonates ( polymers having

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.

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

Poly( ethyleneimine )

Polyallylamine

Brand

Name

Manufacture

r

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.Service

s

Up to 93ºC Water soluble high molecular

weight polymers.

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

D-600 GD-700 GFLAG-56BA-10SBA-58L

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

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

These are required to counter high formation pressures.

Common high density materials are:-Haematite:

Form : Red powderSpecific Gravity:-4.7-5.25 (g/cm3)

An iron ore (Fe2O3),chemically inert and requires little additional water.

BariteForm:-White powder

Specific Gravity:-4.230 (g/cm3)Barite is a barium sulfate material used

to weight drilling mud and cement slurries.

PHYSICAL PARAMETERS UNIT REQUIREMENT

MIX WATER % BY WT. OF

CEMENT

44

FREE FLUID CONTENT % BY VOL. 5.9 (MAX)

COMPRESSIVE STRENGTH AFTER 8 HRS. CURING

i) AT 38 0C, ATMOSPHERIC

PRESSURE

PSI 300 (MIN)

ii) AT 60 0C, ATMOSPHERIC

PRESSURE

PSI 1500 (MIN)

THICKENING TIME AT 520 C,5160 PSI

RAISED IN 28 MINUTES

MINUTES 90 (MIN)

120 (MAX)

MAXIMUM CONSISTENCY ( 15 TO

30 MIN. STIRRING PERIOD)

Bc 30

Chemical Requirements

1. Magnesium oxide ( MgO), % by mass 6.0 (max.)

2. Sulphur trioxide (SO3), % by mass 3.0 (max.)

3. Loss on ignition, % by mass 3.0 (max.)

4. Insoluble residue, % by mass 0.75 (max.)

5. Tricalcium Silicate, % 65.0 (max.)

48.0 (min.)

6. Tricalcium Aluminate, % 3.0 (max.)

7. Tricalcium Aluminoferrite + twice Tricalcium Aluminate, % 24.0 (max.)

8. Total Alkali content expressed as Sodium oxide equivalent,

%

0.75 (max.)

A. Factors influencing slurry design

1. Well depth, diameter & casing size.

2. BHCT, BHST, BHP, Mud density.

3. Sample of cement, cement additive,

mixing water.

slurry design is carried out under well

simulated conditions with cementing

materials to be used at site.

B. Cement Slurry Parameters.

Density – well control & security.

Thickening Time – sufficient pumping

time.

Rheology – n’, k’, critical velocity.

Fluid Loss Control – viscosity, lost

circulation.

Free Water – channeling, settling.

Compressive Strength – WOC

All these parameter should be taken care

to maintain well security & integrity.

Mixing Devices The mixing device for

preparation of wellcement slurries shall beapprox. 1 Ltr. The twospeed mixer should becapable of 4000 RPM +200 RPM under slowspeed and capable of12000 RPM + 500 RPMunder high speed.

Screening The sample of cement to

be tested shall bepassed through 850micron (Sieve No. 20BSS).

Constant Speed Mixer

SIGNIFICANCE

Density of cement slurry is adjusted to:

Balance the formation pressure.

Control the loss of slurry in weak zones.

Facilitate the effective mud removal/displacement.

Normally, slurry density is kept higher than the mudfor facilitating the displacement of drilling fluid fromannulus. The density difference of 0.2 to 0.5 gm/cc isnormally recommended between mud and cementslurry.

Sp. Gr. can be adjusted byvarying water - cement ratio

The min. water requiredAmount to keep the initial

consistency less than 30 Bc

Max. water requiredWater separation of slurry

be kept less than 1.4%.

TEST PROCEDUREThe method for measuring thedensity of cement slurry is by useof a pressurized fluid balance.

Pressurized Fluid

Balance

SIGNIFICANCE

The thickening time is the time elapsed from the initial

application of temperature and pressure to the time required

for the slurry to reach a consistency of 100 Bc.

Thickening time is a function of temperature / pressure, typeof cement used and various additives dosed.

Thickening time of the slurry must be established forrealistic conditions to ensure adequate pumping time forslurry placement.

Thickening time is determined at BHCT conditions.

Thickening time of the cement slurry should be sufficientwhich should enable the operator to place the slurry to thepredetermined depth safely. Some margin of safety is alsoincluded so as to cover the time of break down whilecementing.

EQUIPMENTThe apparatus used is High Pressure High Temperature (HPHT) Consistometer.

HPHT CONSISTOMETER

It consist of rotating cylindrical slurry container equipped with a

stationary paddle, all enclosed in a pressure vessel capable of

withstanding well simulation pressure and temperatures.

TEST PROCEDURE•The filled slurry container is placed in the pressure vessel, then the head assembly of the pressure vessel is closed.•During the test period the temperature and pressure of the cement slurry in the slurry cup is increased in accordance with the well simulation test schedule.

SIGNIFICANCE

When cement slurry is placed against permeableformation, then water from the cement slurry enters intothe formation. This phenomenon is known as “Fluid Loss”or water loss of cement slurry. If this is not controlledseveral serious consequences may occur which lead tocement job failure or poor cementation job.As the volume of the aqueous phase decreases, theslurry density increases, as a result the performance of thecement slurry (viz. rheology, thickening time etc.) maydiverge from the original design.If sufficient fluid is lost to the formation, the slurrybecomes unpumpable, causes premature prehydration ofslurry which can lead to annulus plugging, incompletedisplacement.Cement filtrate can damage production zones.

Tests at temperature less than or equal to

88 0C• Conditioning: Atmospheric/ Pressurized

Consistometer/Stirred Fluid Loss Cell

• F/L determination: Any F/L Cell

Tests at temperature greater than 88 0C• Conditioning: Pressurized Consistometer/Stirred

Fluid Loss Cell

• F/L determination: Any F/L Cell

Atmospheric Consistometer HTHP Filter Press

SIGNIFICANCE: Different flow patterns may be encountered depending on conduit geometry,

flow velocity and physical properties of fluid.

They are characterized by the velocity and movement of the particles in different cross sections of the conduit and accordingly defined as plug flow, laminar flow or turbulent flow.

Rheology of cement slurry is defined by Bingham-Plastic or Power Law Model or Herschel-Bulkley Model of flow mechanics, which is governed by:

• Mud displacement in the annulus

• Frictional pressure drop in annulus

• Hydraulic horse power required to place the cement.

It also depends on the casing size and hole size including washouts. Slurry is designed for turbulent flow (wells with low annular clearance) or plug flow (wells with high annular clearance).

The Fann viscometer isused for calculating therheological properties ofcement slurry. Theviscometer is directindicating instrumentpowered by a motor witha gear box.

Slurry with low criticalvelocity is desired tofacilitate the cementingoperation and result ingood cementation.Fann VG

Meter

The Fann viscometer is used for

calculating the rheological properties of

cement slurry. The viscometer is direct

indicating instrument powered by a motor

with a gear box.

Slurry with low critical velocity is desired to

facilitate the cementing operation and

result in good cementation.

SIGNIFICANCE The strength developed by cement dependson various factors such as water cement ratio,temperature, time and additives used. For testingpurpose it is necessary to define all theseconditions.

The minimum compressive strength requiredto hold the casing and to seal the formation is 500psi. Compressive strength of set cements massincreases with time and temperature.

API recommends a maximum pressure of3000 psi, probably because higher pressures arehaving very little effect on compressive strengthduring hydration process.

The slurry is first preparedand then poured intomoulds in an evenlydistributed pattern andpuddling is done using aglass rod to minimizesegregation.

The moulds are nowplaced in a curingchamber and the desiredtemperature and pressureis applied. The specimensare then removed andallowed to cool.HPHT Curing

Chamber

The specimen is thentested in acompressive loadingmachine where load isapplied on the blocks.The load at whichmaterial failure takesis noted and knowingthe cross sectionalarea of that specimen,the compressivestrength of that blockcan be determined.

Compressive Strength Testing Machine

SIGNIFICANCE

The cement slurry is conditioned to simulate dynamic placement in awell bore. Slurry is left static to determine if free fluid separates fromthe slurry.It indicates the quantity of fluid separated from the cement slurry intwo hours under static conditions and expressed in percentage of theslurry volume.In case the water separation of cement slurry is very high it can formwater pockets in the annulus leading to the formation of micro channelsin the set cement.Fluid loss reducing agents generally reduce water separation ofcement slurries.The maximum permissible limits of water separation is 1.4%

DETERMINATION OF FREE FLUID SEPARATION

Slurry is prepared as per API recommended Procedure.

Poured immediately into slurry container of a HPHT

consistometer and conditioned as per thickening time test

schedule.

After conditioning, if the tempeature is higher it is cooled to 880

C, pressure released and poured into a graduated cylinder (size

between 232 & 250 mm/ length & dia ratio: 6:1 to 8:1).

The supernatant fluid developed after standing quiescent for 2

hours at 880 C is removed by decantation and measured.

Tube can be kept vertically or in tilted manner.

Free water is measured in ml as free water and is expressed as

% slurry volume.

The technology of slurry design has advanced

so much that the cementing compositions can

be tailored to any well needs.

The following major factors have been found

important which need careful consideration in

the designing of cement slurry

•Maximum available downhole density to

prevent fracturing.

•Thickening time to provide adequate pumping

and placement time with the safety margin.

Fluid loss control to prevent formation of annular rings against permeable zones and loss of hydrostatic pressure with consequent fluid migration problems.

Rheological control to facilitate pumping of cement slurry and control of displacement mechanism.

Compatibility with all other fluids in the borehole (mud, preflush, spacer etc.).

Strength, soundness strength retrogression and permeability.