Cement Additives

(1)

Dowell

(2)

Well Conditions

PROBLEM Well control

over pressure and weak formations Temperature Permeable formations Mud removal Friction pressure Mixability/Pumpability Lost circulation Density Thickening time Fluid Stability Fluid loss control

Plugging/Bridging properties Density SLURRY PARAMETER Rheology Extenders Weighting agents Accelerators Retarders FLAC Dispersants Gelling Agents LCM Extenders ADDITIVE CATEGORY SOLUTIONS

(3)

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

(4)

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

(5)

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%

(6)

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..:

(7)

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)

(8)

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..)

(9)

Calcium Chloride

l

S1, S2, D77

n Most active accelerator

n Range 1-4%

n Effect on Thickening Time

Thickening Time (h:mn)

CaCl

₂

(%BWOC)

91

o

F

103

o

F

113

o

F

0 4:00

3:30

2:32

2 1:17

1:11

1:10

(10)

Compressive Strength

Compressive Strength at Temperature (psi) 60oF 80oF 100oF CaCl2 (%) 6 hr 12 hr 24 hr 6 hr 12 hr 24 hr 6 hr 12 hr 24 hr 0 NS 60 415 45 370 1260 370 840 1780 2 125 480 1510 410 1020 2510 1110 2370 3950 4 125 650 1570 545 1245 2890 1320 2560 4450

(11)

Secondary Effects of CaCl

₂

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

(12)

Sodium Chloride

l

Sodium Chloride (D44) as an accelerator

nNot very efficient

nActs as an accelerator < 15% BWOW nPreferred range is 3 - 5 % BWOW

136°F (58°C) 154°F(68°C) 179°F (81°C) 8 6 4

(13)

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 (D13, D81, D800, D801)

n Hydroxycarboxylic acids (D109, D110, D45)

n Inorganic compounds (D93, D74)

(14)

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

(15)

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 BHCT BHCT oo_F_F Retarder 100 200 300 400 140 100 185 125 250 250 310 300 175 300 375 220 300 350 300 400 300 100 Fresh Sea 37% NaCl X X X X X X X X X X X X X X X X X X X X X X X

(16)

Lignosulfonates

l

Low to mid temperature use

n D13 (D81) <185o_F

n D800 (D801) 140o_{- 220}o_F

l

Pulping by-product

n Variable performance

l

Efficiency improved 150

o

_{- 175}

o

_F

l

Tendency to gel at higher concentrations

l

May require dispersion

(17)

Hydroxycarboxylic Acid

l

Powerful retarders

n D110 (D109) - 175o_{- 325}o_F

n D45 (salt dispersant)

l

Detrimental effect with lattices

l

Some dispersion

(18)

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

(19)

Cellulose

l

CMHEC (D8) - Diacel LWL

n Sometimes used for retardation

n Viscosifying

n Effective to 250o_F

n Some fluid loss control

l

Other fluid loss additives

(20)

Blended Retarders

l

Generally lignosulfonate with other material

n D28 (D150) - 220o_{- +300}o_F

n D121 - 250o_{- 350}o_F

l

Dispersing action as well, especially at high

concentration

l

D121 erratic below 300

o

_F

l

D121 may overdisperse

(21)

D161

l

High Temperature Retarder (>250

o

_F)

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

(22)

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

(23)

D161 Setting Characteristics

psi @ 320 o F to TT @ 350 o F 0 1 2 3 4 5 6 7 8 Conventional D161 Ratio of TTR 50 psi @ 320 o F to TT @ 350 o F

(24)

CS to TT Ratio

D161 D121/D28 D93/D110 D66 (%BWOC) D47 (gps) D158 (gps) Disp (% or gps) 35 0.05 0.5 0.06 35 0.05 0.5 1.00 35 0.05 0.5 1.00 35 0.05 0.5 0.06 35 0.05 0.5 0.06 Retarder (% or gps) D93 (%BWOC) 1.25 ---1.50 ---2.00 ---0.24 0.40 0.40 0.40

Thickening Time (hr:min) at 350oF:

5:27 3:32 4:12 4:12 8:53

Compressive Strength (hr:min) at 320oF:

TTR 50 psi TTR 500 psi 8:18 10:10 19:03 21:48 25:46 28:59 35:52 38:45 30:13 33:27

(25)

Compressive Strength Development

2 4 6 8 10 12 14 16 18 20 22

Time to reach compressive

strength at 320 ° F (hr) 3000 psi 500 psi 50 psi

(26)

Slurry Density

CHANGING OF SLURRY DENSITY

LIGHTER MORE WATER* ABSORBENT LIGHT MATERIAL LOWER DENSITY

(27)

Cement Extenders

Bentonite

LITEPOZ* 3 D35 LITEPOZ 7 D61

TXI Lightweight Cement Diacel D D56 Expanded Perlite D72 Gilsonite D24 KOLITE* D42 Sodium Metasilicate D79 Sodium Silicate D75

Slurry Density (lb/gal) Extender or Lightweight System 6 7 8 9 10 11 12 13 14 15 15 12 _14.7 10.8 13.6 12 14.2 11 14.5 10.6 13.8 12 15 11 14.5 14.5 11.5 11.5 12 15

(28)

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

(29)

Bentonitic Extenders

• General properties:

•

BENTONITE CLAY

BENEFICIATED (PEPTIZED) NON - TREATED

MONTMORILLONITE - D20 (FRESH)

ATTAPULGITE - D128 (SEA)

n

n _{Water based extender} n

(30)

Bentonite (D20)

l Allow addition of extra water, yet control free water

n Optimum water content must be determined

n Starting point - 5.3% additional water per 1% bentonite

l Additional water means

n Reduced cost (increased yield)

n Reduced strength

n Increased permeability

n Reduced resistance to chemical attack by brines

l Viscosifies slurries (requires dispersant >6% D20)

l Slurry stabilizer (free water and sedimentation)

(31)

Chemical Extenders

l

Silicates

n React with cations in cement system (Ca2+_{, Mg}2+₎

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

(32)

Point of Departure

20 68 100 0 20 40 60 80 100 0 20 40 60 80 100 120 140 160 180 200 Time (min) Consistency (Bc) 470* 468* 245* 170*

* 24 hr compressive strength (psi) of slurry removed and cured at 170oF Class G + 2% D79 (12.5 ppg)

(33)

D75 Slurries

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 + 0.28 gps D75 @ 12.5 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 Class G + 0.24 gps D75 @ 13.0 ppg Tests at 118o_F

(34)

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

(35)

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

(36)

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

(37)

Microsilica (silica fume)

l Amorphous sub-micron spheres

l Pozzolanic properties (reactive)

l Low bulk density (<15 lb/ft3₎

l Provides some slurry stability

l Frequently blended with other lightweight additives (HiLITE -blend with D124)

l Bulk blending is difficult with dry material

l Liquid can be stored with minimal agitation

l Concentration up to 20%

l Dispersant is required to effectively disperse in water and prevent gelation

(38)

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

(39)

Lost Circulation Control

l

Reduce density

l

Reduce friction pressure

l

Add LCM

n

Granular

(40)

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

(41)

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

(42)

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)

(43)

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

(44)

Dispersants

l Cement slurry rheology

n Volume of particles / total volume

n Particle interactions

n Aqueous phase rheology

Change with dispersants

l Why dispersants ?

(45)

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

(46)

Dispersant Action

CEMENT Dispersant Molecule SO₃ SO₃

C

₂

SH

- -

₀

3

S

+

_Ca

+ +

_Ca

+ -

₀

3

S

C

₂

SH

(47)

-Use of TIC D80 in ETD

Yield Value ( /100ft 2 ) 20 15 10 5 5 10 15 20 30 5 10 15 20 30 25 25 Overdispersed Yield value Free water Viscosity Plastic Viscosity (Cp) Free Water (%) Underdispersed Acceptable Range

(48)

Use of TIC D604M in ETD

Yield Value ( lb /100ft 2 ) 20 15 10 5 5 10 15 20 30 5 10 15 20 30 25 25 Yield value Free water Viscosity Plastic Viscosity (Cp) Free Water (%) Underdispersed Acceptable Range

(49)

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:

(50)

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

(51)

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:

Slurry yield Free water Thickening time Settling Bulk Shrinkage REDUCED INCREASED n n _Hydrostatic n n _{Slurry density} n n _{Plastic viscosity} n n _{Yield point} n n _{Compressive strength} n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n

(52)

Thickening Time versus Density

THICKENING TIME THICKENING TIME

160

Thickening Time (min)

(53)

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

(54)

(55)

**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 uD60, D59(MT,ND,S) D112(MT,LD,S) n Non-Ionic Polymer uD127(LT,S) B30(LT,S) D159(L-MT,AD,L) D160(L-MT,AD,S) n Anionic Polymer uD603(MT,ND,L) D143, D158(M-HT,HD,L), D156(LT,AD,S)

(56)

Dispersant Effect on Fluid Loss

Mechanism of action

• Disperse cement grains and improve packing --> reduced permeability • Flocculate w/salt ---> plugging action

• •

FILTER CAKE

(57)

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

(58)

Slurry Density

Less Water Changing Slurry Density

Lighter _Heavier

More

Water* _WaterLess

Absorbent Light Material Heavy Material Dispersant Lower Density Higher Density

(59)

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

(60)

Strength Retrogression

Above 230o_{F cement undergoes:}

n Reduction in strength

n Increase in permeability

l Due to crystalline changes in CSH gel

CSH gel ---> alpha dicalcium silicate

amorphous crystalline

strong, impermeable weak, permeable

C/S = 1.5 C/S = 2.0

l Prevented by addition of 30 - 40% BWOC silica (reduces C/S ratio of C-S-H gel)

(61)

D30 Silica Sand & D66 Silica Flour

Particle size US Mesh Additional Water Specific gravity Applications: High density Low density Settling Problems

NAME _{SILICA SAND}D30 _{SILICA FLOUR}D66

70 - 200 ±10% 1.12 gal/sk 2.63 Preferred Alternative Alternative Preferred > 200 + 12% 1.34 gal/sk 2.63