4- Cementing Additives Cl Jun-00-a

Cementing Additives Module CF204 15 Sep 99

Well Conditions ADDITIVE CATEGORY

PROBLEM

SLURRY PARAMETER

Well control over pressure and weak formations

Density

Extenders Weighting agents

Temperature

Thickening time

Accelerators Retarders

Permeable formations

Fluid Stability Fluid loss control

FLAC

Mud removal Friction pressure Mixability/Pumpability

Rheology

Dispersants Gelling Agents

Lost circulation

Plugging/Bridging properties Density

Abnormal and specialized conditions: Heat retrogression Hydration product Foamers Stabilized foam capability Foam Foaming tendency Etc.

2

SOLUTIONS

{

LCM Extenders Silica Foaming agent & stabilizers Anti foamers

Cementing additives  Accelerators and retarders – Change thickening time – Alter rate of compressive strength development  Extenders – Reduce slurry density – Increase slurry yield  Weighting agents – Increase slurry density  Dispersants – Improve mud removal – Improve mixability / reduced water slurries – Reduce friction pressure (Lower ty and Pv)  Fluid Loss Control  Lost Circulation Material (LCM)

3

Cement Additives

 Accelerators and Retarders  Change thickening time  Alter rate of compressive strength development  Extenders  Reduce slurry density  Increase slurry yield  Weighting Agents  Specialty:  Increase density  Antifoam/defoamer agents  Dispersants  Bonding agents  Improve mud removal  Expansive additives  Improve mixability  Gas migration control additives, et  Reduce friction pressure  Thixotropic systems  Fluid Loss Control  Lost Circulation Material

4

Antifoam Agents  Why use antifoam agents ? – Prevent slurry gelation – Prevent pump cavitation – Allow true slurry density to be mixed and pumped  To be effective they must: – Be insoluble in the foaming fluid – Be more surface active than the foaming fluid  Mechanism of action: – Spread on foam surface with lower surface tension – Enter foam reducing film and causing rupture  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)

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Conductor pipe  Prevents washing out under rig  Customer wants short rig downtime  Quick setting cement - rapid

development of compressive strength  Accelerated slurries, e.g.:

– Neat cement + NaCl (D44) 3-5% – Neat Cement + CaCl2 (S1) 2-4% – Neat cement + seawater  Cemented with stab-in or just driven

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Accelerators  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 CS-H gel structure  Can be used to offset retarding effects of other additives  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)  D44 - NaCl - <10%BWOW  Seawater

– Check consistency - near river mouths  D77 - CaCl2 in liquid form - 0.2 to 0.4 gps  ARCTIC SET For Low Temperature

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Sodium Chloride  Sodium Chloride (D44) as an accelerator Not very efficient Acts as an accelerator < 10% BWOW Preferred range is 3 - 5 % BWOW Effect of temperature:

Time to reach 100 Bc Slurry consistency (hr)

8

136°F (58°C)

6

154°F(68°C)

4

179°F (81°C) 210°F (99°C)

2

0

8

0

5

10

15

20

25

NaCl IN MIX WATER (% BWOW)

30

Surface Casings  Unconsolidated zones  Low Temperatures (New challenge in

deep O/S - temperature very low)  Large volumes of slurry  Light weight slurries  Strong slurry at shoe  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 Density CHANGING OF SLURRY DENSITY

LIGHTER MORE WATER*

LIGHT

ABSORBANT

MATERIAL

LOWER DENSITY

15.6 Class A Neat Cement 15.8 Class G 16.4 Class H * D124 IS AN EXCEPTION AS AN EXTENDER AS IS FOAM CEMENT

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Classification of Extenders  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)  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.  Very low density materials – Nitrogen - FOAM CEMENT - need stabilizer – Ceramic microspheres - D124 (LITEFIL) - Max 5000 psi / no VIP

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Cement Extenders Extender or Lightweight System

6

7

8

Slurry Density (lb/gal) 9 10 11 12 13 14

Bentonite

15

11.2 12

LITEPOZ 3 D35 LITEPOZ 7 D61

14.7 13.6

10.8

TXI Cement D911

14. 13. 2

12

Trinity Lite-Wate Cement D49

11.9

Diacel D D56

15

7

Gilsonite D24

12

14. 5 13. 8 15

KOLITE D42

12

15

11

Expanded Perlite D72

10.6

Sodium Metasilicate D79

11

14.5

Sodium Silicate D75

11.5

14.5

LITEFIL D124 Foamed Cement Microsilica D154 / D155

12

9

12 15

6 11

15

Chemical Extenders  Sodium silicates and metasilicates – React with cations in the cement (Ca 2+, 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  D79, SODIUM METASILICATE - dry  D75, SODIUM SILICATE - liquid

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Lightweight Aggregates  POZZOLANS: Diatomaceous Earth (D61, D602) & Fly Ash( D35) – React with calcium hydroxide in cement – Corrosion brine resistance – Low permeability – Thermal resistance  KOLITE (D42) and GILSONITE (D24): – Coal (D42) and Asphalt (D24) based materials – Effective lost circulation materials (Granular) – Kolite (D42) is inert  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  MICROSILICA (Silica Fume, D154, D155): – Pozzolanic material – Good slurry properties (Increase Rc)

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Ultra Lightweight Extenders  Ceramic microspheres, LITEFIL D124 (Limit

5000 psi) – Ceramic or glass microspheres – Inert – Density range: 8.5 lb/gal to 14.5 lb/gal

 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 Casings  Workable sections  13 3/8” over 3000 feet deep  Often 2 stage cementing  Low cost  Extended lead and neat tail, e.g.:

– Prehydrated bentonite 2-3% – D75 0.28 gps + 1% S1 – 15.8 ppg tail slurries  All slurries to be retarded  Can have some fluid loss control

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Hydration of Cement I

II

IV

hr

min

18

III

V

days

I.

PRE - INDUCTION PERIOD

II.

INDUCTION PERIOD

III.

ACCELERATION PERIOD

IV.

DECELERATION PERIOD

V.

DIFFUSION PERIOD

STAGES 1 and 2: Pre Induction and Induction Periods

Ca

Al OH Ca Si SO4

Seconds

ETTRINGITE

Hours C - S - H Gel PROTECTIVE LAYERS STOPS REACTIONS ???? - PUMPING TIME

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Retardation of cement slurries  Applications

– Intermediate and production strings – Squeeze and cement plugs – High temperature and depth  Chemical Classes of retarders

– – – – – – –

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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

Mechanisms of Retardation  Factors affecting mechanism of action – Chemical nature of retarder – Chemical composition of cement  Retarders : Theories of mechanism of action – Adsorption theory – Precipitation theory – Nucleation theory – Complexation theory  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 Retardation  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  Precipitation theory – Ca and OH react with Retarder to Precipitate an Impermeable Layer  Nucleation theory – Retarder Adsorbs to Poison Nucleation and Growth Sites  Complexation theory – Retarder Complexes with Ca to Minimise the Driving Force for Reaction and Prevent Formation of Nucleation Sites

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Cement Retarders Retarder

BHCT oF 100

D13/D81

100

D13/D81 with Dispersant

100

D800/D801

200

300

185 250

D800/D801 with D93/L10

250 175

300

D28/D150

220

D28/D150 with D121

25

300 100

375

300 300

D28/D150 with D93 D161

310 300

D110 with D93/L10

D74

400

140

125

D110

Fresh Sea 37% NaCl

350 400

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

140 250

450

X

Fluid Loss in Cement Slurries  Definition: – Filtrate (aqueous solution) lost to the formation – Filter cake deposited at formation face – Cement particles left in annulus

 Why cement loses water: – Differential pressure – Permeable medium (formation) – Water/cement ratio > hydration needs

 Fluid loss stages: – Dynamic fluid loss – Static fluid loss

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Effect of Fluid Loss on Slurry Properties

 Thickening time and yield point versus water

concentration  Damage to some formations by filtrate  Gas migration through thick filter cake and through poor quality cement  Other properties:      

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REDUCED Slurry yield Free water Thickening time Settling Bulk Shrinkage Mud removal efficiency

     

INCREASED Hydrostatic (psi/ft) Slurry density Plastic viscosity Yield point Compressive strength Bonding

TH ICK EN

ING

Yield Value

Thickening Time (min)

160

Thickening Time versus Density

TI M E

40

E YIELD VALU

15.6

28

Slurry Density (ppg)

16.4

Additives for Fluid Loss Control  Particulate FLACs

D20, D600, D134  Latex FLAC D600 (MT,AD,L), D134

Water Soluble Polymers  Cellulose Derivative

D60, D59(MT,ND,S), D112 (MT,LD,S)  Non-Ionic Synthetic Polymer D159(LT-MT,AD,L), D160 (LT-MT,AD,S)  Anionic Synthetic Polymer D603 (MT,ND,L), D143, D158 (MT-HT,HD,L), D156 (LT,AD,S)

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Dispersants with FLACs Mechanism of action •• ••

Disperse cement grains and improve packing --> reduced permeability Flocculate w/salt ---> plugging action WITHOUT DISPERSANT

FILTER CAKE

RANDOM PACKING HIGH PERMEABILITY

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WITH DISPERSANT

ORDERED PACKING LOW PERMEABILITY

Acceptable Fluid Loss Limits Typical Values: (API, 1000 psi)  Prevention of gas channeling  Liner cementing  Casing cementing

30 - 50 ml/30 min < 50 ml/30 min 200 - >300 ml/30

min  Horizontal well cementing < 50 ml/30 min  For squeeze cementing – Formation with K < 1 md 200 ml/30 min – Formation with K > 1 md <100 md 100 - 200 ml/30 min – Formation with K > 100 md 35 - 100 ml/30 min  High density slurries: < 50 ml/30 min

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Production Casings  Isolate production zones  Small diameter casings  Cost less important  Good bonding  Usually has fluid loss

control  Low friction pressures  Mud removal is important  15.8 ppg or more slurries  All slurries to be retarded

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Dispersants  Cement slurry rheology

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

Change with dispersants  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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Dispersants 

Types:  Superplasticizers D65 D80 - D80A D604M - D604 AM D145A (the only one for D300 to work)

 Plasticizers Lignosulphonates Cement retarders (D13 , D 81 , D800, D801) Mud Thinners

 Organic salts and acids D45, D121

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Dispersant Action SO33

C2SH- + Ca + - 03S CEMENT

POLY C2SH - + Ca + - 03S DISPERSANT MOLECULE

SO33

 Amount of dispersant adsorbed depends on concentration  Cement grain surfaces become uniformly negatively  Alike signs repel one another ---> dispersion

36

Slurry Density CHANGING OF SLURRY DENSITY

LIGHTER

HEAVIER

MORE WATER*

MORE WATER

LIGHT

ABSORBANT

MATERIAL

HEAVY MATERIAL

DISPERSANT

LOWER

HIGHER

DENSITY

DENSITY

15.6 Class A Neat Cement 15.8 Class G 16.4 Class H * D124 IS AN EXCEPTION AS AN EXTENDER AS IS FOAM CEMENT

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LESS WATER

Weighting Agents  Requirements

– –

High specific gravity Compatible particle size and distribution (settling) – Low water adsorption (efficiency) – Availability and acceptable cost – Purity and consistency of product – Inert  Commonly used weighting agents Code

Agent

SG

Additional water

D31 BARITE 4.22 0.024 gal/lb D76 HEMATITE 4.95 0.0023 gal/lb (D907 CEMENT 3.20 0.0529 gal/lb) D157 Manganese O (Mn3 O4) Mg tetraoxide

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Strength Retrogression  Above 230 oF BHST unstabilized cement will

undergo: – A reduction in strength – An increase in permeability  Due to structural change in C-S-H gel  Prevented by the addition of 30 - 40% BWOC

silica reduces

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

D30 Silica Sand & D66 Silica Flour NAME Particle size -US Mesh Add. Water Specific gravity

D30 SILICA SAND 70 - 200 ±10% 1.12 gal/sk 2.63

D66 SILICA FLOUR > 200 + 12% 1.34 gal/sk 2.63

Applications: High density

Preferred

Alternative

Low density

Alternative

Preferred

Settling Problems

Alternative

Preferred

Mixing Problems (Rheology)

Preferred

Alternative

Use above 300°F

Alternative

Preferred

41

Antisettling Agent D153  Controls free water and/or sedimentation  Compatible with all Dowell products and

cements  No significant effects on slurry properties,

except rheology  Dry-blend or prehydrated (preferred), fresh or sea water  Temperature range: up to 302 F (150 C)  Concentration range: 0.1 to 1.5%BWOC (depending on density) 42