Dowell
Cement Additives
Additives 1
Dowell
Well Conditions ADDITIVE CATEGORY
PROBLEM Well control over pressure and weak formations
SLURRY PARAMETER Density
SOLUTIONS 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: Hydration product Strength retrogression Foamers Stabilized foam capability Foam
Foaming tendency
{
LCM Extenders Silica Foaming agent & stabilizers Anti foamers Additives 2
Dowell
Cement Additives l Accelerators and Retarders n Change thickening time n Alter rate of compressive strength development
l Extenders n Reduce slurry density n Increase slurry yield
l Weighting Agents n Increase density
l Dispersants n Improve mixability n Reduce friction pressure
Additives 3
Dowell
Cement Additives l Fluid Loss Control l Lost Circulation Material l Specialty: n Antifoam/defoamer additives n Bonding agents n Expansive additives n Gas migration control additives n Gelling and suspending additives n Foaming additives
Additives 4
Dowell
Conductors l Prevents washing out under rig l Short rig downtime l Quick setting cement - rapid development of compressive strength l Accelerated slurries, e.g..: n Neat cement + NaCl (D44) 3-5% n Neat Cement + CaCl2 (S1) 2-4% n Neat cement + seawater
l Lightweight slurries Additives 5
Dowell
Surface Casings l Unconsolidated zones l BOP support l Protect surface waters l Prevent fluid flow l Very large volumes of slurry l Light weight slurries l Strong slurry at shoe (accelerated) l Extended lead with neat tail, e.g..: n
Prehydrated bentonite 2-3% 12.8 ppg
n
Neat cement + 0.5-1% S1 15.8ppg
Additives 6
Dowell
Thickening & Setting Time l Control to n Reduce WOC (reduce rig-time) n Reduce chance for fluid/gas flow n Allow time to complete job
l Affected by n Temperature n Pressure n Cement type (class and grind) n Mixing and placement methods n Accelerators and Retarders n Other additives (salt, dispersant, fluid loss additives)
Additives 7
Dowell
Accelerators l Applications n Shallow casings (conductor, surface) n Low temperature conditions n Offset retarding effects of other additives
l Additives n Calcium Chloride (CaCl2) - 1-4% n Sodium Chloride (NaCl) - <15% n Other salts (carbonates, silicates, nitrates, etc..) n Organic chemicals (formates, oxalic acid, etc..)
l Reduced water
Additives 8
Dowell
Calcium Chloride l S1, S2, D77 n Most active accelerator n Range 1-4% n Effect on Thickening Time
CaCl2
Thickening Time (h:mn) 91oF 103oF 113oF
(%BWOC)
0 2 4
4:00 1:17 1:15
3:30 1:11 1:02
2:32 1:10 0:58
Additives 9
Dowell
Compressive Strength Compressive Strength at Temperature (psi) CaCl2 (%)
6 hr
60oF 12 hr
0 2 4
NS 125 125
60 480 650
24 hr 415 1510 1570
6 hr
80oF 12 hr
24 hr
45 410 545
370 1020 1245
1260 2510 2890
6 hr
100oF 12 hr
24 hr
370 1110 1320
840 2370 2560
1780 3950 4450
Additives 10
Dowell
Secondary Effects of CaCl2 l Increased temperature n Heat of solution of CaCl2 n Additional accelerating effect (on surface?) n Casing expansion
l Increased rheology (gelation) l Possible permeability increase n Reduced sulfate resistance
Additives 11
Dowell
Sodium Chloride l Sodium Chloride (D44) as an accelerator nNot very efficient nActs as an accelerator < 15% BWOW nPreferred range is 3 - 5 % BWOW Effect of Salt concentration:
Time to reach 100 Bc (hr)
8
136°F (58°C) 6
154°F(68°C) 4
179°F (81°C) 210°F (99°C)
2
0
0
5
10
15
20
25
30
NaCl in Mix Water (% BWOW) Additives 12
Dowell
Retardation of Cement Systems l Applications n Intermediate and production strings n Surface and conductor casings (long pumping times) n Squeeze and cement plugs n High temperature and depth
l Chemical Classes of Retarders n Lignosulphonates n Hydroxycarboxylic acids n Inorganic compounds n Cellulose derivatives n Blended retarders n Special materials
(D13, D81, D800, D801) (D109, D110, D45) (D93, D74) (D8) (D28, D150, D121) (D161)
n (Blend of above components) Additives 13
Dowell
Mechanisms of Retardation l Factors affecting mechanism of action n Chemical nature of retarder n Chemical composition of cement
l Theories of mechanism of action n Adsorption theory n Precipitation theory n Nucleation theory n Complexation theory
l Possible negative effects on slurries n Gelation n Dispersion n Increased fluid loss n Incompatibility Additives 14
Dowell
Cement Retarders Retarder
BHCT oF 100
D13/D81
100
D13/D81 with Dispersant
100
D800/D801
200
300
185 250 250
D800/D801 with D93/L10 175
310 300 300
D110 with D93/L10 220
D28/D150
300
D28/D150 with D93
300
D161
100
375
300
D28/D150 with D121
D74 - for RFC only
400
140
125
D110
Fresh Sea 37% NaCl
350 400
140
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X 250
450
X
Additives 15
Dowell
Lignosulfonates l Low to mid temperature use n D13 (D81) <185oF n D800 (D801) 140o - 220oF
l Pulping by-product n Variable performance
l Efficiency improved 150o - 175oF l Tendency to gel at higher concentrations l May require dispersion
Additives 16
Dowell
Hydroxycarboxylic Acid l Powerful retarders n D110 (D109) - 175o - 325oF n D45 (salt dispersant)
l Detrimental effect with lattices l Some dispersion l Recommended retarder for silicate extended slurry
Additives 17
Dowell
Inorganic Retarders l Retarder aid - D93 n Has no retarding capacity by itself n Extends temperature range for other retarders n Detrimental effect on fluid loss
l Sodium Chloride (D44) n Retards at concentrations over 20% n May over-retard at low temperatures
l D74 - Retarder for RFC (D53 version)
Additives 18
Dowell
Cellulose l CMHEC (D8) - Diacel LWL n Sometimes used for retardation n Viscosifying n Effective to 250oF n Some fluid loss control
l Other fluid loss additives n D59, D60, D112
Additives 19
Dowell
Blended Retarders l Generally lignosulfonate with other material n D28 (D150)
- 220o - +300oF
n D121
- 250o - 350oF
l Dispersing action as well, especially at high concentration l D121 erratic below 300oF l D121 may overdisperse
Additives 20
Dowell
D161 l High Temperature Retarder (>250oF) l Rapid Strength Development n Lengthens Dormant Period; not Hydration Rate
l Reduced Sensitivity to n Concentration Error n Temperature Error
l Effective in Fresh Water, Seawater, and Salt Water l Liquid
Additives 21
Dowell
Applications l Cementing Long Liners and Casing n Single Stage vs. Two-Stage Jobs n Single Slurry Replacing a Lead and Tail Slurry
l Squeeze Cementing l Kick-off Plugs l Coiled Tubing Applications
Additives 22
Dowell
RatioRatio of TTR psi50@psi 320@oF320oF of 50 TTR oF350oF to TTto @TT 350@
D161 Setting Characteristics 8 7 Conventional
6 5 4 3 2 1
D161
0 0
2
4
6
8
10
12
Thickening Time @ 350oF Additives 23
Dowell
CS to TT Ratio D161 D121/D28 D66 (%BWOC) D47 (gps) D158 (gps) Disp (% or gps) Retarder (% or gps) D93 (%BWOC)
35 0.05 0.5 0.06 1.25 ---
35 0.05 0.5 1.00 1.50 ---
35 0.05 0.5 1.00 2.00 ---
D93/D110 35 0.05 0.5 0.06 0.24 0.40
35 0.05 0.5 0.06 0.40 0.40
4:12
8:53
Thickening Time (hr:min) at 350oF: 5:27
3:32
4:12
Compressive Strength (hr:min) at 320oF: TTR 50 psi TTR 500 psi
8:18 10:10
19:03 21:48
25:46 35:52 30:13 28:59 38:45 33:27
Ratio of TTR 50 psi @ 320oF toTT @ 350oF 1.5
5.4
6.1
8.5
3.4
Dyckerhoff Red Label at 16.0 ppg
Additives 24
Dowell
Time to reach compressive strength at 320°F (hr)
Compressive Strength Development 22 20 18 16 14 12 10 8 6 4 2 0
3000 psi
500 psi 50 psi
2
3
4
5
6
7
8
9
10
Thickening time @ 350°F (hr)
Additives 25
Dowell
Slurry Density CHANGING OF SLURRY DENSITY
LIGHTER MORE WATER*
LIGHT
ABSORBENT
MATERIAL
LOWER DENSITY
15.6 Class A Neat Cement 15.8 Class G 16.4 Class H * D124 and Foamed Cement are exceptions Additives 26
Dowell
Cement Extenders Extender or Lightweight System
6
7
8
Slurry Density (lb/gal) 9 10 11 12 13 14
Bentonite
15 15
11.5 12
LITEPOZ* 3 D35
14.7 13.6
10.8
LITEPOZ 7 D61 TXI Lightweight Cement
14.2
12
Diacel D D56
14.5
11
Expanded Perlite D72
10.6
13.8
Gilsonite D24
12
15
KOLITE* D42
12
15
Sodium Metasilicate D79
11
Sodium Silicate D75
11.5
LITEFIL* D124 Foamed Cement
9
14.5 12
6
15
Microsilica LiteCRETE* Cement
14.5
11 10.5
15 12.5
* Mark of Schlumberger Additives 27
Dowell
Classification of Extenders l Water “absorbing” extenders n Clays (Bentonite) - D20, D128 n Chemical extenders (Silicates) - D75, D79
l Low density solids n Pozzolans (Fly ashes) - D35, D56, D61, D602 n KOLITE* and gilsonite - D42, D24 n Expanded perlite - D72 n Silica fume (Microsilica) - D154, D155
l Very low density materials n Nitrogen - Foamed Cement n Ceramic microspheres - D124 (LITEFIL*) * Mark of Schlumberger Additives 28
Dowell
Bentonitic Extenders BENTONITE CLAY
BENEFICIATED (PEPTIZED)
MONTMORILLONITE - D20 (FRESH)
NON - TREATED
ATTAPULGITE - D128 (SEA)
• General properties: n n n n n n n n n n
Water based extender n n SG = 2.65 n n Dry blended or pre-hydrated Concentration range, 0-20% BWOC nn Density range, 11.5 - 15 ppg n n
Economical and widely available Decreases compressive strength, increases permeability Viscosifies slurries Provides fluid loss control Additives 29
Dowell
Bentonite (D20) l Allow addition of extra water, yet control free water Optimum water content must be determined n Starting point - 5.3% additional water per 1% bentonite n
l Additional water means Reduced cost (increased yield) n Reduced strength n Increased permeability n Reduced resistance to chemical attack by brines n
l Viscosifies slurries (requires dispersant >6% D20) l Slurry stabilizer (free water and sedimentation) l High concentrations (>12%) provide fluid loss control (<400 mL/30 min l May be prehydrated (1% prehydrated = 4% dry) l Inhibited by salt Additives 30
Dowell
Chemical Extenders l Silicates n React with cations in cement system (Ca2+, Mg2+) n Form viscous, gelatinous silicate gel
- Capable of binding extra water - Low free water separation n Low rheologies for turbulent flow n Better properties and mixing than bentonite slurries n No inherent fluid-loss control n Relatively low concentrations required n Ca - Silicate formed acts as accelerator n Use D110 (or D109) retarders
l D79, Sodium Metasilicate - dry l D75, Sodium Silicate - liquid Additives 31
Dowell
Point of Departure Class G + 2% D79 (12.5 ppg)
Consistency (Bc)
20 68100 100
Schedule 4g6 (118oF)
80
170*
245*
60 40
468*
470*
20 0 0
20
40
60
80
100 Time (min)
120
140
160
180
200
* 24 hr compressive strength (psi) of slurry removed and cured at 170oF
Point of Departure is the time at which the slurry begins to increase in consistency. Additives 32
Dowell
D75 Slurries
Class G + 0.28 gps D75 @ 12.5 ppg
Shear 24 hr Compressive Strength (min) (psi) 20 650 90 640 140 470 260 200 POD is 90 minutes - plateau of 40 Bc at 150 minutes
Class G + 0.24 gps D75 @ 13.0 ppg
D109 POD Time to 70 Bc (gps) (hr:mn) (hr:min) 0 1:50 +4:00 0.04 2:00 3:15 0.07 4:10 5:35 Tests at 118oF
Test at 131oF
Additives 33
Dowell
Silicate Slurry Design l Point of departure is the thickening time n Optimize D75/D110
l Use D110 (D109) as retarder (erratic behavior with lignosulfonates) l Calcium chloride has little effect on compressive strength l Mixing n Do not mix D75 with any other liquid additive n Add CaCl2, then D75, then D110 if using fresh water n Keep water/D75 solution agitated (keep gel suspended)
Additives 34
Dowell
Lightweight Aggregates l POZZOLANS: Fly Ash( D35), Volcanic Ash and Diatomaceous Earth (D61, D602) n React with calcium hydroxide in cement n Corrosion brine resistance n Low permeability n Thermal resistance
l EXPANDED PERLITE (D72) n Inert material and does not affect thickening times n Normally add 2 - 6% BWOC bentonite to prevent floatation n Gives reduced cement permeability n Bridging action at higher concentrations
l MICROSILICA (Silica Fume, D154, D155): n Pozzolanic material n Good slurry properties Additives 35
Dowell
Pozzolans l Naturally occurring n Volcanic ashes n Diatomaceous earth (D61)
l Artificial n Fly ash u
Type F (D35, D48) - most common
u
Type C (D132) - more reactive (cementitious)
l Key Properties n React with Ca(OH)2 u
Contribute strength
u
Reduce permeability
n Increased brine resistance Additives 36
Dowell
Microsilica (silica fume) l l l l l l l l l l
Amorphous sub-micron spheres Pozzolanic properties (reactive) Low bulk density (<15 lb/ft3) Provides some slurry stability Frequently blended with other lightweight additives (HiLITE blend with D124) Bulk blending is difficult with dry material Liquid can be stored with minimal agitation Concentration up to 20% Dispersant is required to effectively disperse in water and prevent gelation Additives n D154 - dry n D155 - liquid Additives 37
Dowell
Ultra-Lightweight Extenders l Ceramic microspheres, LITEFIL* D124 n Ceramic or glass microspheres n Inert n Specific gravity 0.7 - 0.8 n Fragile - pressure limitation of 5,000 psi n Density range: 8.5 lb/gal to 14.5 lb/gal n Enhanced strength and permeability
l Foamed cement systems n Nitrogen injected into slurry with foamer n Very low densities > 6.0 lb/gal n Good mechanical properties * Mark of Schlumberger Additives 38
Dowell
Lost Circulation Control lReduce density lReduce friction pressure lAdd LCM n Granular n Flake
Additives 39
Dowell
Granular Lost Circulation Materials l D42 - KOLITE* additive n Ground coal n SG - 1.3 n Concentration - 5 - 25 lb/sk n Slurry stability is key
l D24 - Gilsonite n Ground asphaltinic material n SG - 1.07 n Similar to D42 n Temperature limitation of 300oF due to softening
l Mechanism n Bridging n Mixing difficulties at high concentrations Additives 40
Dowell
Flake Lost Circulation Materials l D29 (Cellophane flake) n Concentration - 1/8 to 1/2 lb/sk
l D130 (Polyester flakes) n Concentration - 1/8 to 1/2 lb/sk
l Mechanisms n Form “mat” on fractures, vugs, etc..
l Handling n Mixing difficulties at high concentrations
Additives 41
Dowell
Intermediate Casings l Protect weak or sensitive formations (production) l May be 2 stage l Low cost l Extended lead and neat tail l Most slurries are retarded l May require fluid loss control l May require special properties (e.g.. gas migration control)
Additives 42
Dowell
Production Casings l Isolate production zones l Smaller diameter casings l Cost less important l Good bonding l Fluid loss control is usually required l Low friction pressures l Mud removal is important l 15.8 ppg or more slurries l All slurries to be retarded
Additives 43
Dowell
Dispersants l Cement slurry rheology n Volume of particles / total volume n Particle interactions n Aqueous phase rheology Change with dispersants l Why dispersants ? n Reduce viscosity and yield point n Reduce friction pressures n Improve cement slurry mixability n Reduced water slurries (density up to 18.0 lb/gal) n Improve efficiency of fluid loss additives Additives 44
Dowell
Dispersants l TIC* Additive l Superplasticizers n PNS - D65, D80, D604M, D604AM n PMS - D145
l Plasticizers n Cement retarders (D13, D81, D800, D801) n Mud thinners
l Organic salts and acids n D45 n D121 * Mark of Schlumberger Additives 45
Dowell
Dispersant Action C2SH-
+Ca+
-0
SO3
3S
CEMENT
C2SH-
+Ca+
-0
3S
Dispersant Molecule
SO3
• Amount of dispersant adsorbed depends on concentration • Cement grain surfaces become uniformly negative • Like signs repel one another ---> dispersion Additives 46
Dowell
Use of TIC D80 in ETD 20
30
30
Underdispersed
Yield Value ( /100ft2)
25
Overdispersed
Yield value
Acceptable Range
25
15 20
20
Free water 10
15
Free Water 15 (%)
10
10
5
Viscosity
Plastic Viscosity 5 (Cp)
0.00
0.05
5
0.10
0.15
0.20
0.25
D80 (gal/sk)
Note: ETD Cement at 185°F Additives 47
Dowell
Use of TIC D604M in ETD 20
30
30
Underdispersed
Yield Value (lb/100ft2)
25
Yield value
25
Acceptable Range
15
20
20
Viscosity 10
15
Free Water 15 (%)
10
10
5
Plastic Viscosity 5 (Cp)
0.00
0.05
Free water
0.10
0.15
0.20
5
0.25
D604M (gal/sk)
Note: ETD Cement at 185°F Additives 48
Dowell
Fluid Loss in Cement Slurries l Definition: n Filtrate lost to the formation n Filter cake deposited at formation face n Cement particles left in annulus
l Why cement loses water: n Differential pressure n Permeable medium (formation)
l Fluid loss stages: n Dynamic n Static
Additives 49
Dowell
Dynamic vs. Static Fluid Loss l Dynamic n Placement n Loss is proportional to time n Filter cake reaches pseudo-stable thickness n Density increases n Slurry properties change
l Static n After placement n Loss is proportional to square root of time n Cake grows n May result in annular restrictions u
Causes loss of hydrostatic pressure Additives 50
Dowell
Effect of Fluid Loss l Damage to some formations by filtrate l Gas migration through thick filter cake and through poor quality cement l Other properties: REDUCED n n Slurry yield n n Free water n n Thickening time n n Settling n n Bulk Shrinkage n n Mud removal efficiency (?)
INCREASED n n Hydrostatic n n Slurry density n n Plastic viscosity n n Yield point n n Compressive strength n n Bonding
Additives 51
Dowell
Thickening Time (min)
160
Thickening Time versus Density
Yield Value
TH ICK EN ING TIM E
40
E YIELD VALU
15.6
Slurry Density (ppg)
16.4 Additives 52
Dowell
Mechanisms of Fluid Loss Control l Reduce cement filter cake permeability n Particulate materials to fill voids n Polymer particles to plug pores n Change cement particle distribution with dispersants
l Increase viscosity of aqueous phase n Water soluble polymers n Small effect compared to permeability reduction
Additives 53
Dowell
Mechanisms
Particle Plugging
Polymer Plugging Additives 54
Dowell
FLAC* Additives l Particulate n Gel - D20 n Latex - D600 (MT,M-HD,L) D134(HT,HD,L) n Microgels - D300, D500(AD,LT,L) l Water Soluble Polymers n Cellulose Derivative u D60, D59(MT,ND,S) D112(MT,LD,S) n Non-Ionic Polymer u D127(LT,S) B30(LT,S) D159(L-MT,AD,L) D160(L-MT,AD,S) n Anionic Polymer u D603(MT,ND,L) D143, D158(M-HT,HD,L), D156(LT,AD,S) n Cationic Polymer - D73.1(M-HT,ND,L) n FLAC Enhancer - D136 (below 200oF) * Mark of Schlumberger Additives 55
Dowell
Dispersant Effect on Fluid Loss Mechanism of action •• ••
Disperse cement grains and improve packing --> reduced permeability Flocculate w/salt ---> plugging action
FILTER CAKE WITHOUT DISPERSANT
WITH DISPERSANT
RANDOM PACKING
ORDERED PACKING
HIGH PERMEABILITY
LOW PERMEABILITY Additives 56
Dowell
Acceptable Fluid Loss Limits l Gas zones
30 - 50 mL/30 min
l Liner
< 50 mL/30 min
l Casing
200 - 300 mL/30 min
l Horizontal well
<50 mL/30 min
l High density slurries:
<50 mL/30 min
l Squeeze : n Formation with K < 1 md
200 mL/30 min
n Formation with K 1 md - 100 md
100 - 200 mL/30 min
n Formation with K > 100 md
35 - 100 mL/30 min
Neat cement = +1000 mL/30 min Additives 57
Dowell
Slurry Density Changing Slurry Density
Lighter
Heavier
More Water*
Less Water
Light Material
Absorbent
Heavy Material
Lower Density
Less Water
Dispersant
Higher Density
15.6 Class A Neat Cement 15.8 Class G 16.4 Class H * D124 and Foamed Cement are exceptions Additives 58
Dowell
Weighting Agents l Requirements n High specific gravity n Compatible particle size and distribution (settling) n Low water adsorption (efficiency) n Availability and acceptable cost n Purity and consistency of product n Inert
l Commonly used weighting agents Code
Agent
SG
Additional water
D31 D76 D157
Barite Hematite MicroMax Cement
4.33 4.95 4.80 3.15
0.024 gal/lb 0.0023 gal/lb 0.0011 gal/lb 0.049 gal/lb Additives 59
Dowell
Strength Retrogression Above 230oF cement undergoes: n Reduction in strength n Increase in permeability l Due to crystalline changes in CSH gel CSH gel ---------> alpha dicalcium silicate amorphous strong, impermeable C/S = 1.5
crystalline weak, permeable C/S = 2.0
l Prevented by addition of 30 - 40% BWOC silica (reduces C/S ratio of C-S-H gel) CSH gel + silica ---------> Tobermorite C/S = 0.8
Tobermorite
---------> Xonotlite + Gyrolite C/S + 1.0
C/S + 0.8
Care should be given to production temperatures Additives 60
Dowell
D30 Silica Sand & D66 Silica Flour Particle size US Mesh
D30 SILICA SAND 70 - 200
Additional Water
±10% 1.12 gal/sk
Specific gravity
2.63
NAME
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 Additives 61
Dowell
Antisettling Agent D153 l Controls free water and/or sedimentation l Compatible with all Dowell products and cements l No significant effects on slurry properties, except rheology l Dry-blend or prehydrated (preferred), fresh or sea water l Temperature range: less than 302oF (150oC) l Concentration: 0.1 to 1.5%BWOC (depending on density) Additives 62
Dowell
Slurry Stability
Additives 63
Dowell
Antifoam Agents l Purpose n Prevent slurry gelation n Allow true slurry density to be mixed and pumped n Prevent pump cavitation (due to aeration)
l Mechanism of action: n Lower surface tension n Reduces film and causes rupture
l Types of antifoam agents n Polyglycol ethers
Solid : D46 (0.2 lb/sk) Liquid : D47 (0.05 gal/sk) n Silicones
Liquid : D144 (0.01 - 0.02gal/sk) Liquid : M45 (0.05 gal/sk) Additives 64
Dowell
