Cementing Additives

2Well ConditionsADDITIVE CATEGORY

PROBLEMWell controlover pressure andweak formationsTemperature

Permeable formations

Mud removalFriction pressureMixability/PumpabilityLost circulation

Abnormal and specialized conditions:Heat retrogressionFoamersFoamEtc.

Density

Thickening time

Fluid StabilityFluid loss control

Plugging/Bridging propertiesDensity

Hydration productStabilized foam capabilityFoaming tendency

SLURRY PARAMETER

Rheology

ExtendersWeighting agents

AcceleratorsRetardersFLAC

DispersantsGelling Agents

SilicaFoaming agent &stabilizersAnti foamers

LCMExtenders

SOLUTIONS

{

3Cementing additivesz Accelerators and retarders

Change thickening time Alter rate of compressive strength development

z Extenders Reduce slurry density Increase slurry yield

z Weighting agents Increase slurry density

z Dispersants Improve mud removal Improve mixability / reduced water slurries Reduce friction pressure (Lower ty and Pv)

z Fluid Loss Controlz Lost Circulation Material (LCM)

4Cement Additivesz Accelerators and Retarders

z Change thickening timez Alter rate of compressive strength development

z Extendersz Reduce slurry densityz Increase slurry yield

z Weighting Agentsz I n c r e a s e d

z Dispersantsz Improve mud removalz Improve mixabilityz Reduce friction pressure

z Fluid Loss Controlz Lost Circulation Material

e n s i t yz Antifoam/defoamer agentszz Specialty:

z Bonding agentsz Expansive additivesz Gas migration control additives, etc.z Thixotropic systems

5Antifoam Agentsz Why use antifoam agents ?

Prevent slurry gelation Prevent pump cavitation Allow true slurry density to be mixed and pumped

z To be effective they must: Be insoluble in the foaming fluid Be more surface active than the foaming fluid

z Mechanism of action: Spread on foam surface with lower surface tension Enter foam reducing film and causing rupture

z Types of antifoam agents Polyglycol ethers Solid : D46 (0.2 lb/sk)

Liquid : D47 (0.05 - 0.07 gal/sk) Silicones Liquid : D144 (0.01 - 0.02gal/sk)

Liquid : M45 (0.05 gal/sk)

6Conductor pipez Prevents washing out under rigz Customer wants short rig downtimez Quick setting cement - rapid

development of compressive strength

z Accelerated slurries, e.g.: Neat cement + NaCl (D44) 3-5%

Neat Cement + CaCl2 (S1) 2-4%

Neat cement + seawater

z Cemented with stab-in or just driven

7Acceleratorsz Used to shorten stages I and II and to accelerate stages III and IV -

hydration of main cement phases is increased plus a change in the C-S-H gel structure

z Can be used to offset retarding effects of other additivesz S1 - CaCl2 - 1 to 4%BWOC

Check type of CaCl2 - S1 is 77% pure

Disolution in water is exothermic (see field data handbook page 700.004)

z D44 - NaCl -

8Sodium Chloride

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z Sodium Chloride (D44) as an acceleratorNot very efficientActs as an accelerator < 10% BWOWPreferred range is 3 - 5 % BWOW

136F (58C)

154F(68C)

179F (81C)210F (99C)

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00 5 10 15 20 25 30

NaCl IN MIX WATER (% BWOW)

Effect of temperature:

9Surface Casingsz Unconsolidated zonesz Low Temperatures (New challenge in

deep O/S - temperature very low)z Large volumes of slurryz Light weight slurriesz Strong slurry at shoez Extended lead slurries with neat tail,

e.g.: Prehydrated bentonite 2-3% 12.8 ppg

Neat cement + 0.5-1% S1 15.8ppg

2/3 lead - 1/3 tail annulus height

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Slurry DensityCHANGING OF SLURRY DENSITY

LIGHTER

MOREWATER*

ABSORBANTLIGHT

MATERIAL

LOWERDENSITY

Neat Cement15.6 Class A15.8 Class G16.4 Class H

* D124 IS AN EXCEPTION AS AN EXTENDER AS IS FOAM CEMENT

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Classification of Extendersz Water based extenders

Water Clays (Bentonite) - D20, D128 - check viscosity - do not let it built up Chemical extenders (Sodium Silicates) - D75, D79 (need Ca ++ to work)

z Low density solids Pozzolans (Fly ashes) - D35, D56, D61, D602 Kolite and gilsonite - D42, D24 Expanded perlite - D72 Microsilica - D154 (solid) , D155 (liquid version) (Experience in MBZ for LW

slurries / High compressive strength with D155 in horizontal wells) with D155.

z Very low density materials Nitrogen - FOAM CEMENT - need stabilizer Ceramic microspheres - D124 (LITEFIL) - Max 5000 psi / no VIP

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Cement Extenders

BentoniteLITEPOZ 3 D35LITEPOZ 7 D61TXI Cement D911Trinity Lite-Wate Cement D49Diacel D D56Expanded Perlite D72Gilsonite D24KOLITE D42Sodium Metasilicate D79Sodium Silicate D75LITEFIL D124Foamed CementMicrosilica D154 / D155

Slurry Density (lb/gal)Extender orLightweight System 6 7 8 9 10 11 12 13 14 15

1512 14.7

10.8 13.6

12 14.213.711.9

11 14.5

10.6 13.812 15

1512

11 14.514.511.5

9 12

1561511

11.2

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Bentonitic Extenders

General properties: Water based extender SG = 2.65 Dry blended or pre-hydrated Concentration range, 0-20% BWOC Density range, 11.5 - 15 ppg

Economical and widely available Decreases compressive strength,

increases permeability Viscosifies slurries (Lots of solids)

BENTONITE CLAY

BENEFICIATED (PEPTIZED) NON - TREATED

MONTMORILLONITE - D20(FRESH)

ATTAPULGITE - D128(SEA)

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Chemical Extendersz Sodium silicates and metasilicates

React with cations in the cement (Ca2+, Mg2+) Form viscous, gelatinous silicate gel

- Capable of binding extra water- Low free water separation

Low rheologies for turbulent flow Better properties and mixing than bentonite slurries Better compressive strength than bentonite slurries No inherent fluid-loss control (use D112 FLAC) Relatively low concentrations required Ca - Silicate formed acts as accelerator Use D110 (or D109) retarders - beware of POD

z D79, SODIUM METASILICATE - dryz D75, SODIUM SILICATE - liquid

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Lightweight Aggregatesz POZZOLANS: Diatomaceous Earth (D61, D602) & Fly Ash( D35)

React with calcium hydroxide in cement Corrosion brine resistance Low permeability Thermal resistance

z KOLITE (D42) and GILSONITE (D24): Coal (D42) and Asphalt (D24) based materials Effective lost circulation materials (Granular) Kolite (D42) is inert

z EXPANDED PERLITE (D72) Inert material - does not affect thickening times Normally add 2 - 6% BWOC bentonite to prevent floatation Gives reduced cement permeability Bridging action at higher concentrations

z MICROSILICA (Silica Fume, D154, D155): Pozzolanic material Good slurry properties (Increase Rc)

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Ultra Lightweight Extenders

z Ceramic microspheres, LITEFIL D124 (Limit 4500 psi) Ceramic or glass microspheres

Inert

Density range: 8.5 lb/gal to 14.5 lb/gal

z Foamed cement systems Nitrogen injected into slurry with foamer

Very low densities achieved > 6.0 lb/gal

Good mechanical properties

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Intermediate Casingsz Workable sectionsz 13 3/8 over 3000 feet deepz Often 2 stage cementingz Low costz Extended lead and neat tail, e.g.:

Prehydrated bentonite 2-3%

D75 0.28 gps + 1% S1

15.8 ppg tail slurries

z All slurries to be retardedz Can have some fluid loss control

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Hydration of Cement

I II III IV V

min hr days

I. PRE - INDUCTION PERIOD

II. INDUCTION PERIOD

III. ACCELERATION PERIOD

IV. DECELERATION PERIOD

V. DIFFUSION PERIOD

I. PRE - INDUCTION PERIOD

II. INDUCTION PERIOD

III. ACCELERATION PERIOD

IV. DECELERATION PERIOD

V. DIFFUSION PERIOD

19

STAGES 1 and 2: Pre Induction and Induction Periods

SO4CaAl OH Ca Si

Seconds

ETTRINGITEETTRINGITE

HoursC - S - H Gel

PROTECTIVE LAYERS STOPS REACTIONS ???? - PUMPING TIME

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Retardation of cement slurriesz Applications

Intermediate and production strings Squeeze and cement plugs High temperature and depth

z Chemical Classes of retarders Lignosulphonates (D13, D81, D800, D801) Hydroxycarboxylic acids (D109, D110) Inorganic compounds (D93, D74) Cellulose derivatives (D008) Blended retarders (D28, D150, D121) (Blend of above components) Sugar is also a cement retarder

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Mechanisms of Retardationz Factors affecting mechanism of action

Chemical nature of retarder Chemical composition of cement

z Retarders : Theories of mechanism of action Adsorption theory Precipitation theory Nucleation theory Complexation theory

z Possible negative effects on slurries Gelation Dispersion Increased fluid loss Incompatibility Slows the development of the compressive strength (D028)

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Mechanisms of Retardationz Adsorption theory

Adsorbtion of Retarder on to Cement Surfaces to Inhibit Contact with Water and Make the Surfaces Hydrophobic

Modify CSH Gel to Make it Less Permeable

z Precipitation theory Ca and OH react with Retarder to Precipitate an Impermeable Layer

z Nucleation theory Retarder Adsorbs to Poison Nucleation and Growth Sites

z Complexation theory Retarder Complexes with Ca to Minimise the Driving Force for Reaction

and Prevent Formation of Nucleation Sites

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Properties of Individual Retardersz Lignosulphonates (Low to Medium Temperatures)

Most Common Retarders Derived from Wood Pulp Active Ingredients Alcohols and Carbohydrates MW 20,000 to 30,000 Work Better with Low C3A which Consumes Retarder D800/D801 higher temperature stability than D13/D81 Work by Adsorption and Nucleation

z Carboxylic Acids (Medium to High Temperatures) Carboxyl and OH groups strongly Complex Calcium Work by Nucleation Powerful Retarders: Easily over-retard at T < 90oC D110 and D109 Different Dilutions of Same Chemical Very sensitive to concentration

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Properties of Individual Retardersz Blended

D28: Sugars plus Lignin Aminez High Temperature Applicationsz Strongly Complexing z Works by Complextation and Nucleation Poisoningz Can Separate Into IndividualComponents

D121: Mixed Dispersant and Retarderz Lignosulphonate and HydroxyCarboxylic Acidz High Temperature Applications often with D028

z Inorganic Retarders (Mid to High Temperature) D93 - Boraxz A retarder: Adsorption ?z A Retarder Aid by Stabilizing Other Retarders

D161 - A New High Temperature Retarder (Blend) - Impart viscosity build up.

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Cement Retarders

D13/D81

D13/D81 with Dispersant

D800/D801

D800/D801 with D93/L10

D110

D110 with D93/L10

D28/D150

D28/D150 with D121

D28/D150 with D93

D74

D161

BHCT oFRetarder 100 200 300 400

140

100 185

125 250

250 310

300175

300 375

220 300

350300

400300

100 140

450250

100

Fresh Sea 37%NaCl

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Fluid Loss in Cement Slurriesz Definition:

Filtrate (aqueous solution) lost to the formation

Filter cake deposited at formation face

Cement particles left in annulus

z Why cement loses water: Differential pressure

Permeable medium (formation)

Water/cement ratio > hydration needs

z Fluid loss stages: Dynamic fluid loss

Static fluid loss

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Effect of Fluid Loss on Slurry Properties

Slurry yield

Settling

Plastic viscosityYield point

z Thickening time and yield point versus water concentrationz Damage to some formations by filtratez Gas migration through thick filter cake and through poor quality cementz Other properties:

Free waterThickening time

BondingBulk ShrinkageMud removal efficiency

REDUCED INCREASEDHydrostatic (psi/ft)Slurry density

Compressive strength

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Thickening Time versus Density

THICKENING TIME

YIELD VALUE

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Slurry Density (ppg)

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15.6 16.4

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Mechanisms of Fluid Loss Controlz Reduce cement filter cake permeability

Particulate materials to fill voids Polymer particles to plug pores Polymer film over cement particles/pores Change cement particle distribution with dispersants

z Increase viscosity of aqueous phase Addition of water soluble polymers Also reduce filter cake permeability Effect small compared to permeability reduction

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Additives for Fluid Loss Controlz Particulate FLACs

D20, D600, D134z Latex FLAC

D600 (MT,AD,L), D134z Cationic Polymer

D73.1 (MT-HT,ND,L)

Water Soluble Polymersz Cellulose Derivative

D60, D59(MT,ND,S), D112 (MT,LD,S)z Non-Ionic Synthetic Polymer

D159(LT-MT,AD,L), D160 (LT-MT,AD,S)z Anionic Synthetic Polymer

D603 (MT,ND,L), D143, D158 (MT-HT,HD,L), D156 (LT,AD,S)

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Dispersants with FLACsMechanism of action

Disperse cement grains and improve packing --> reduced permeabilityFlocculate w/salt ---> plugging action

WITHOUT DISPERSANT WITH DISPERSANTFILTER CAKE

ORDERED PACKING

LOW PERMEABILITY

RANDOM PACKING

HIGH PERMEABILITY

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Acceptable Fluid Loss LimitsTypical Values: (API, 1000 psi)

z Prevention of gas channeling 30 - 50 ml/30 minz Liner cementing < 50 ml/30 minz Casing cementing 200 - >300 ml/30 minz Horizontal well cementing < 50 ml/30 minz For squeeze cementing

Formation with K < 1 md 200 ml/30 min

Formation with K > 1 md 100 md 35 - 100 ml/30 min

z High density slurries: < 50 ml/30 min

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Production Casings

z Isolate production zonesz Small diameter casingsz Cost less importantz Good bondingz Usually has fluid loss controlz Low friction pressuresz Mud removal is importantz 15.8 ppg or more slurriesz All slurries to be retarded

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Dispersantsz Cement slurry rheology

Volume of particles / total volume Inter-particle interactions Aqueous phase rheology

Change with dispersantsz Why dispersants ?

Reduce viscosity and yield point Turbulent flow easier to achieve (Companies like cement in turbulent

flow for liners) Reduce friction pressures Improve cement slurry mixability (Lower Ty) Reduced water slurries (density up to 18.0 lb/gal) Improve efficiency of fluid loss additives

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Dispersantsz Types:z Superplasticizers

D65D80 - D80AD604M - D604 AMD145A (the only one for D300 to work)

z PlasticizersLignosulphonatesCement retarders (D13 , D 81 , D800, D801)Mud Thinners

z Organic salts and acidsD45, D121

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Dispersant Action

POLYCEMENT

C2SH- + Ca + - 03S

C2SH - + Ca + - 03S

DISPERSANTMOLECULE

SO33

SO33

z Amount of dispersant adsorbed depends on concentrationz Cement grain surfaces become uniformly negativelyz Alike signs repel one another ---> dispersion

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Workable Range of D80 Dispersant ETD vs DTD Cements

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30UNDERDISPERSED

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0.00 0.05 0.15 0.250.200.10

D80 (gal/sk)

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OVERDISPERSED

YIELD VALUE

FREE WATER

VISCOSITYPLASTIC VISCOSITY(cp)15

FREEWATER (%)

D80

NOTE: WITH ETD CEMENT AT 186F

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Slurry Density

LESSWATER

CHANGING OF SLURRY DENSITY

LIGHTER HEAVIER

MOREWATER*

MOREWATER

ABSORBANTLIGHT

MATERIALHEAVY

MATERIAL DISPERSANT

LOWERDENSITY

HIGHERDENSITY

Neat Cement15.6 Class A15.8 Class G16.4 Class H

* D124 IS AN EXCEPTION AS AN EXTENDER AS IS FOAM CEMENT

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Weighting Agentsz Requirements

High specific gravity Compatible particle size and distribution (settling) Low water adsorption (efficiency) Availability and acceptable cost Purity and consistency of product Inert

z Commonly used weighting agentsCode Agent SG Additional water

D31 BARITE 4.22 0.024 gal/lbD76 HEMATITE 4.95 0.0023 gal/lb

(D907 CEMENT3.20 0.0529 gal/lb)D157 Manganese O (Mn3 O4) Mg tetraoxide

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Strength Retrogression

z Above 230 oF BHST unstabilized cement will undergo: A reduction in strength

An increase in permeability

z Due to structural change in C-S-H gelz Prevented by the addition of 30 - 40% BWOC silica reduces

C/S ratio of C-S-H gel)

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D30 Silica Sand & D66 Silica Flour

Particle size-US Mesh

Add. Water

Specific gravity

Applications:

High density

Low density

Settling Problems

Mixing Problems(Rheology)

Use above 300F

NAME D30 D66SILICA SAND SILICA FLOUR70 - 200

10%1.12 gal/sk

2.63

Preferred

Alternative

Alternative

Preferred

Alternative

Alternative

Preferred

Preferred

Alternative

Preferred

> 200

+ 12%1.34 gal/sk

2.63

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Antisettling Agent D153

z Controls free water and/or sedimentationz Compatible with all Dowell products and cementsz No significant effects on slurry properties, except rheologyz Dry-blend or prehydrated (preferred), fresh or sea waterz Temperature range: up to 302 F (150 C)z Concentration range: 0.1 to 1.5%BWOC (depending on

density)

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New Fluid Loss Additives D159/D160z Adjustable fluid loss control

z Accelerating effect at low temperature, less than 140 F

z Working temperature range in fresh water: up to 230 F

z Density range: 12.5 to 18 ppg

z Concentration range: D159: 0.3 to 0.7 gps (depending on density)

D160: 0.5 to 1.5%BWOC

z Salt up to 15%BWOW

z Incompatible with S1; erratic results with D110; best extended with D20

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New Fluid Loss Additive D300z Adjustable fluid loss control

z Low cost

z No retarding effect at low temperatures

z Working temperature range in fresh water: up to 230 F

z Density range: 12.5 to 15.8 ppg

z Concentration range: 0.35 to 1.1 gps (same for any density)

z Salt up to 10%BWOW

z Compatible with S1; best extended with D75

z Incompatible with D80 and D20

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New HT Retarder D161

z Medium to high temperature retarderz Low costs - reduced WOCz Controllable and predictable thickening times

Reproducible lab tests

Rapid compressive strength development

Less sensitive to small concentration/mixing errors

z Working temperature range: 250 to 450 F (fresh water)z Density range: 14 to 18 ppgz Concentration range: 0.6 to 2.5 gpsz Synergetic effect with D158/D159z Incompatible with D600 and D134

Well ConditionsCementing additivesCement AdditivesAntifoam AgentsConductor pipeAcceleratorsSodium ChlorideSurface CasingsSlurry DensityClassification of ExtendersCement ExtendersBentonitic ExtendersChemical ExtendersLightweight AggregatesUltra Lightweight ExtendersIntermediate CasingsHydration of CementSTAGES 1 and 2: Pre Induction and Induction PeriodsRetardation of cement slurriesMechanisms of RetardationMechanisms of RetardationProperties of Individual RetardersProperties of Individual RetardersCement RetardersFluid Loss in Cement SlurriesEffect of Fluid Loss on Slurry PropertiesThickening Time versus DensityMechanisms of Fluid Loss ControlAdditives for Fluid Loss ControlDispersants with FLACsAcceptable Fluid Loss LimitsProduction CasingsDispersantsDispersantsDispersant ActionWorkable Range of D80 Dispersant ETD vs DTD CementsSlurry DensityWeighting AgentsStrength RetrogressionD30 Silica Sand & D66 Silica FlourAntisettling Agent D153New Fluid Loss Additives D159/D160New Fluid Loss Additive D300New HT Retarder D161