Quartz School For Well Site Supervisors Quartz School For Well Site Supervisors Quartz School For Well Site Supervisors Quartz School For Well Site Supervisors

Quartz School for Well Site Supervisors Module – 7 Well Cementing Ops.

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Section – 1 Well Cementing – I

Day 1

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Well Cementing

Agenda • Primary Cementing

• Slurry Properties, Additives and Lab Testing • Cementing Calculations 3

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• Cement Chemistry

Knowledge of Cementing (1) •

The Well Site Supervisor must be able to:to:– Calculate the volumes of a Primary cement job. – Calculate the volumes of a Secondary/Remedial cement job. – Give clear instructions to the cementer on the objectives of the job. – Monitor and witness the pumping of the cement from start to finish. – Be able to react quickly and make decisions if cement job is not going to plan. – Evaluate the competency of a cementing engineer – Apply the rigors of the steps of the cementing program contained within the Drilling Program.

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– Understand associated hydrostatics of the cementing operation.

Knowledge of Cementing (2) •

Over and above the tasks of the Well Site Supervisor, the Well Engineer must be able to:

– Understand the hydraulics and hydrostatics during a cementing operation. – Understand the mechanics of cement placement techniques. – Evaluate the completed cement job based on logging data and /or associated pressure tests. – Formulate a plan by which cementing service companies can be measured for quality of cementing operations.

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– Rationalize the design of a cement job based on objectives, cost and technology.

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Primary Cementing

Primary Cementing - Objectives • Definition and purposes

• Cement job design basics • Equipment

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• Types of casing and cementing

Primary Cementing

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Fresh water

Shale Salt water or oil

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The introduction of a cementacious material into the annulus between casing and open hole to : – Provide zonal isolation – Support axial load of casing strings and strings to be run later – Provide casing support and protection – Support the borehole

Types of Casings • Conductor • Surface

or or liner

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• Intermediate • Production casing

Conductor •

30 ‘’ casing in 36’’ hole or 20 ‘’ casing in 26’’ hole @ 30 ft - 200 ft

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Purpose: – Prevents washing out under the rig – Provides elevation for flow nipple Challenges: – Possible occurrence of shallow water flows – Low temperatures (offshore) – Drilling through gas hydrates under deep water conditions (offshore) Others: – Large excess – Stab-in cementing common – Accelerated neat cement

Thru-Drill Pipe Cementing (Stab-in) • Key Points:

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Less cement contamination Less channelling Small displacement volume Pump until cement to surface Less job time (rig time) Less cement

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– – – – – –

Outside Cementing (Top Job) • Key points:

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Bring cement to surface Macaroni tubing used Max. depth 250-300 ft High friction pressures Non-standard connections

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Tubing moved during job

– – – – –

Surface •

16 ‘’ casing in 20 ‘’ hole or 13 3/8” 3/8” casing in 17 ½” hole @ 100 ft – 3000 ft

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Purpose: – Protect surface fresh water formation – Case off unconsolidated or loss areas – Provide a competent mechanical base for subsequent operations (BOP, etc.) Challenges: – Possible occurrence of shallow water flows – Low temperatures (offshore) – Drilling through gas hydrates (offshore) Others: – Light weight lead and neat tail slurries – Large excess ( 50 - 150 %)

Intermediate Casing(s) •

Purpose: – Isolate hole into workable sections

Challenges: – Potential problems: over-pressured, loss zones, salt formations or heaving shales – Narrow pressure window, between pore

@ bottom & frac @ top 13 3/8” casing in 17 ½” hole or 9 5/8” casing in 12 ¼” hole @ 3000 to 10,000 ft (vertical or deviated) 14

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Intermediate Casing(s) • Others :

13 3/8” casing in 17 ½” hole or 9 5/8” casing in 12 ¼” hole @ 3000 to 10,000 ft (vertical or deviated) 15

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– Often need a two-stage job – Best cementing practices are required – Cemented to surface or to previous casing shoe – Typically filler slurries followed by high compressive tail – Specialised slurries (light, heavy, salt etc)

Two Stage Cementing • Key Points:

1st Stage

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Stage Collar

– Separation and isolation of zones – Reduces hydrostatic – Can leave zone in the annulus uncemented (cement at TD and surface)

Production Casing(s) or Liner(s) •

Purpose:

• • • Common sizes: 4 ½”, 5”, 7’’, 9 5/8”

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Subsurface artificial lift Multiple zone completion Screens for sand control

– Covers worn or damaged intermediate string.

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– Isolates the pay zone from other formations and the fluids in them. – Protective housing for production equipment.

Liners Pump Down Plug “Dart” Liner Hanger

Liner Over Lap Previous Shoe

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– Requires less casing – Deeper wells – Small annular clearance – Specialized equipment

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Liner Wiper Plug

• Key Points:

Designing a Cement Job • Compute fluid volumes ( Slurry, Wash, Spacer, displacement volumes )

– Hole capacity – Casing capacity – Annular length

• Low cost implies: – Good mixing and economical pumping

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• based on :

Designing a Cement Job • Check that well security is respected: – Simulate cement pumping process

– – – –

Formation pore pressure Formation fracture pressure Tubular burst pressure Tubular collapse pressure (∆ P)

• Ensure well security when Running In Hole • Check temperature and thickening time 20

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to compute hydrostatic and dynamic pressures and compare them to :

Designing a Cement Job • Check for an efficient mud removal to prevent mud channeling and to ensure good zonal isolation – Optimize the pumping rate – Optimize casing centralization

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Ensure good wall cleaning – Optimize pre-flushes volume, and flow rate

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– Optimize fluid properties

Casing

– Burst Pressure – Collapse Pressure – Tensile Load

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• API casing spec – OD

9 5/8”

– Weight

53.5 lbs/ft (determines ID)

– Grade

C75

– Burst pressure

7430 PSI

– Collapse pressure

6380 PSI

– Thread

Buttress

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• Tapered string used to minimize well cost. • Casing program for well based on :

Thread Types •

8 Round – –

Buttress – –

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VAM – –

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Seals on threads & shoulder Use of couplings

Hydrill – – –

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Seals on threads Use of couplings

Seals on threads & shoulder Integral 2 sets of threads

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Seals on threads Use of couplings

Running Casing

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• Running – Casing crews – Too fast – Landing Casing – Nippling up

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• Inspection of Casing – Tuboscope – Pipe tally • Hole Preparation – Mud condition – Clearance

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Casing Running and Cementing Procedures

A Casing String – Reminder! Casing

Shoe Track

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Float Shoe

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Float Collar

Casing Running Procedures The objective of running casing is to:

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• Prevent the collapse of the borehole during drilling. • Hydraulically isolate the wellbore fluids from the subsurface formations. • Provide a high strength flow conduit for the drilling fluid to the surface • With the BOP permits the safe control of formation pressures.

Casing Running/Cementing Procedures To achieve this the casing must be: Centralized to achieve a good cement bond. Cemented to a sufficient height that provides isolation. Cemented with flow properties that optimize mud removal. Balanced (with fluids) inside and out during cementing to prevent burst or collapse. • Pressure tested after cementing to ensure integrity and stability.

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• • • •

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Casing Running/Cementing Procedures A good cement job depends on:

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Sufficient mud filter cake and mud removal. Correct design densities pumped into the well. Correct use of cementing plugs. Correct displacement. (No over-displacement) Sufficient waiting time for cement to set (WOC). Correct pressure testing procedure after cementing.

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Centralizing the casing • Requires the fitting of centralizers to achieve a minimum stand-off of 67% (API)

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Ridged Centralizer 30

Spiral & Turbulent Centralizers

Fluid Flow Regimes V=0

V=2 x Vav

Turbulent Flow Velocity Profile (Swirling motion)

Laminar and Turbulent Flow regimes are found anywhere (pipe, concentric or eccentric annuli) 31

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Laminar Flow Velocity Profile (Sliding motion)

Flow in an eccentric annulus

V > v Always

Do

v

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V

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Dp

Un - Centralized casing

Turbulent Flow Minimal Mud Removal Laminar Flow 33

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Mud Removal

WellClean II Simulator

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Turbulent

Lamina r

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Main Outputs –2D map of –2D map of annulus –2D map of –2D map of flow –2D map of

fluid velocities fluids concentration across the “Risk of mud layer left on the walls” cumulative contact time in turbulent flow regime

Centralizing the casing A.2 Determination of restoringrestoring-force requirements (API 10 D) Field observations indicate hole deviation from vertical on an average varies from zero to approximately 60°. Therefore, an average deviation of 30° is used to calculate restoring-force requirements. For casing diameters 273mm (10 ¾ in) through 508mm (20 in), where casing strings are generally placed in

FR = W sin 30 = 0.5 W where FR is the minimum restoring force, expressed in newtons; W is the weight of 12.19 m (40 ft) of medium linear-mass casing, expressed in newtons. For casing diameters 114mm (4 ½ in) through 244mm (9 5/8 in), where casing strings are generally placed in the

deviated hole sections, the minimum restoring force shall be not less than: 35

FR = 2 W sin 30 = W

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relatively vertical hole sections, the minimum restoring force shall be not less than:

Centralizing the casing Centralizer Spacing Equations T = 0.0408 * TVD * (ρid2 - ρeD2 ) + cos ø * w * S

CS =

F 0.0175 * T * DLS + (WF)b * sin ø

CS F = 2T sin (DLS * ) + (WF)b * CS * sin ø 2

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(WF)b = w + 0.0408 (ρid2 - ρeD2 )

Centralizing the casing Where:

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= = = = = = = = = = = =

tension in the wall of the pipe; lbf adjusted buoyed force centralizer spacing; feet force on each centralizer if spaced CS feet apart; lbf weight per foot of pipe (steel only); lbf/foot buoyancy factor; no units average inclination angle near the centralizer; degrees dogleg severity; degrees/100 feet e.g. DLS = 0.03 true vertical depth to the shoe of the casing; feet ID and OD of the casing; inches distance from the casing shoe to the centralizer; feet mud weights inside and outside the casing; ppg

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T (WF)b CS F w Fb ø DLS TVD d,D S ρ

Centralizing the casing

Which style/type centralizer should be used? Exercise 2 - Homework What is the centralizer spacing required from 6122 ft (36º) to 6302 ft (44º). MD 9989 ft, TVD 4111 ft. Mud inside 15ppg, mud outside 12ppg. Casing is 9 5/8 (D) with ID 8.535 inches (d). DLS is 4.79º.

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Exercise 1 How many 7” casing centralizers should be used to ensure a 67% standoff for 1500ft of liner at a hole angle of 30°? The liner is 29ppf. Mud inside 12ppg. Cement outide 15.8ppg. Centralizer force is 1200 lbf nominal

Equipment On-Shore

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Bulk Plant Silos, WBB, Compressor, Dust Collector

CemCAT

Batch Mixer Diesel Engine 39

Fill

Density, rate, pressure

Equipment Off-Shore

CPS

LAS Liquid Addtive System

Cement Pump Skid

Cement Head Slurry Chief 40

Mixing System

(Sub Sea System)

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Batch Mixer

Cement Heads Surface Expres cement head Oil Level Indicator

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PDD 41

Conventional cement head

Primary Cementing - Summary • Definition and purposes • Types of casing and cementing – Conductor, Surface, Intermediate, Production or Liner

• Cement job design basics – Hole & casing capacities, Formation temperature & pressures, Static & dynamic hydrostatic pressures, Flow regimes, etc

• Equipments (On-shore & off-shore) – Cement pump skid, Cement pump truck, Bulk plant, Batch mixer, Cement heads, Liquid Additive System, Cement mixing system

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– The introduction of a cementacious material into the annulus between casing and open hole to

Break

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10 Minutes

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Cement Chemistry

Agenda

– Silicate phases (C3S and C2S) – Aluminate phases (C3A and C4AF) – False set and flash set

• Strength retrogression at elevated temperatures • Shrinkage 45

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• Manufacture of Portland cement • API cement classification • Hydration of Portland cement

Different Steps of the Cement Manufacturing •

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ARGILLACEOUS- 1 part • Clays • Shales • Slate and Mudstones • Blast furnace slag • Ashes (fly ash) • Cement rock

Grind + Heat Treat in Kiln

Temperature + 1500oC

Clinker Addition of Gypsum

CEMENT CLINKER • • • • •

C3S : Tricalcium Silicate C2S : Dicalcium Silicate C3A : Tricalcium Aluminate C4AF : Tetracalcium Aluminoferrite Ca + Mg Oxides, Ca (OH)2, CaCO3, Na2SO4, etc Controlled Cooling

•

To second grinding mill

Portland Cement ADD 3 - 5% Gypsum (Ca.SO4.2H2O), or Blend of Gypsum + Plaster Pulverise mixture

And Blend

PORTLAND CEMENT C2S + C3S + C3A + C4AF + CaSO4. 2H2O + CaO + MgO + (Na2SO4 + NaKSO4 + CaK2(SO4)2 , or K2SO4 (depending on the cement) 46

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Raw Materials

CALCAREOUS-2 parts • Limestone (CaCO3) • Cement rocks • Chalk • Marl • Marine shells and coral • Alkali waste

Proportioning of Raw Materials • CaO65% – Too Low – Too High

22%

– Too Low – Too High

• Al2O3

Rapid Setting Slow Setting

5%

– Too Low – Too High

• Fe2O3

Raises Temperature Required for Burning Rapid Setting and Gelation

4%

– Too Low – Too High

• MgO 47

1%

Rapid Setting and Gelation Slow Set Unsound Cement if Above 6%

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• SiO2

Low Early Strength Cracking and Unsoundness

Limestone Quarry

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Transportation of Raw Materials to Cement Plant

Cement Manufacturing Processes • Dry process

– More expensive – Less and less used

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• Wet process

Raw Materials Preparation: Dry Process Schlumberger Private


Grinding and blending of dry materials
Less clinker quality
Cheapest process 51

Raw Materials Preparation: Wet Process Schlumberger Private


Grinding and blending of slurried materials


More uniform clinker quality
Expensive process due to fuel required to evaporate the water 52

Burning Process (Continuous Process)

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- length of kiln: up to 200 m - diameter: up to 7 m - weight: up to 1500 tonnes 53

- rotation speed: 1 to 4 RPM - slope: 3.5% - clinkering temperature ≈ 1500°C

Clinkering Zone in the Kiln

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Clinker

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Clinker Composition CaO Bélite C2S Aluminates

Silicates

80 %

3 CaO + SiO2 = C3S

Liquide

C3A C4AF

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{ {

2 CaO + SiO2 = C2S

Alite C3S

3 CaO + Al2O3 = C3A

Aluminates

20 %

4 CaO + Al2O3 + Fe2O3= C4AF

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Cooling Rates & Cement Properties • SLOW COOLING – Enhances Crystallisation Harder to Grind

– More C3A and MgO formed •

More unsoundness

– C3S & C2S more highly ordered • •

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more hydraulically active higher early compressive and lower longer term strength

– Glassy Material • Easier to Grind – Less C3A and free MgO stays in glassy phase •

Less unsoundness

– C3S & C2S less highly ordered •

Lower early strength and higher longer term strength

• OPTIMUM COOLING – 4-5oC/min 1500oC to 1200oC – 18-20oC/min to ambient

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• FAST COOLING

Grinding Process and Storage

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Finish Mill Grinding

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Quality Control of Cement

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- oxide composition - mechanical properties 59

Storage and Distribution System

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Cement Plant 1- Quarry

1

7- Storage 8- Shipment

4- Kiln

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2 7 6- Grinding

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8

4

3

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2- Raw materials

3- Preblending 5- Clinker silo

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API Cement Classification

ISO/API Cement Classification

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• Chemical requirements • Performance requirements

Typical Oxide Composition of Class G and H Cements

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Calculating Cement Phase Composition Oxide Composition:

% C3S % C2S % C3A % C4AF THE BOGUE EQUATIONS TRANSFORM AN OXIDE COMPOSITION TO MINERAL COMPOSITION Mass Balance

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‘N’ Equations ‘N’ Unknowns

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% CaO % SiO2 % Al2O3 % Fe2O3 % SO3

Mineral Composition:

ISO/API Specification of Class G/H Cements • Quality Control: Composition and Performance Specifications ISO/API Schedule 5 Thickening Time (52oC) Consistency after 15 min Stirring 8 hours C/S at 100 degF 8 hours C/S at 140 degF Free Fluid MgO

90 - 120 min Max 30 Bc Min 300 psi Min 1500 psi Max 5.5 ml Max 6%

– – – – – – –

SO3 LOI Insoluble Residue C3S C 3A C4AF + 2 C3A Total Alkalis expressed as sodium oxide equivalent

Max 3% Max 3% Max 0.75% 48% to 65% Max 3% (for HSR) Max 24% Max 0.75%

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– – – – – –

ISO/API Cement Classification (I) • ISO 10426-1:2000 or API Spec 10A • General Construction Cements

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– CLASS A : Intended for use from surface to a depth of 6,000 ft (1,830 m), when special properties are not required. Similar to ASTM Type I cement (high C3A content) – CLASS B : Intended for use from surface to a depth of 6,000 ft (1,830 m). Moderate to high sulphate resistance. Similar to ASTM Type II, and has a lower C3A content than Class A. – CLASS C : Intended for use from surface to a depth of 6,000 ft (1,830 m) when conditions require early strength. Available in all three degrees of sulphate resistance, and is roughly equivalent to ASTM Type III. To achieve high early strength, the C3S content and the surface area are relatively high.

ISO/API Cement Classification (II) • The retarded cements

• Not used anymore (for a long time)

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– CLASS D : Intended for use from 6,000 ft (1,830 m) to 10,000 ft (3,050 m) under conditions of moderately high temperatures and pressures. It is available in MSR and HSR types. – CLASS E : Intended for use from 10,000 ft (3,050 m) to 14,000 ft (4,270 m) under conditions of high temperatures and pressures. It is available in MSR and HSR types. – CLASS F : Intended for use from 10,000 ft (3,050 m) to 16,000 ft (4,880 m) depth under conditions of extremely high temperatures and pressures. It is available in MSR and HSR types.

ISO/API Cement Classification (III) • General Purpose Cements Schlumberger Private

– CLASS G & CLASS H : Intended for use as a basic well cement from surface to 8,000 ft (2,440 m) as manufactured, or can be used with accelerators and retarders to cover a wide range of well depths and temperatures. No additions other than calcium sulphate or water, or both, shall be interground or blended with the clinker during manufacture of Class G and H well cements. They are available in both MSR and HSR types. 69

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Slurry Properties Additives Lab Testing

Slurry Properties •

Free Water & Slurry Sedimentation

– Migrates upward, accumulates in pockets or at top of

cement column. – Results in incomplete zonal isolation

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Density – Balance sub-surface pressures – Cement final strength

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– Water separation from static slurry

Slurry Properties - cont. •

Pumpability (Slurry Consistency) – Length of time slurry remains in a pumpable fluid state

Fluid Loss – Slurry dehydration during placement phase

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Rheology – Slurry flow modeling

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•

Set Cement Properties •

Bonding – Cement - Casing & Cement - Formation

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Sulfate Resistance

•

•

Loss of compressive strength

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Stress cracking

Strength Retrogression – Cement Shrinkage occurs at >230°F (110°C).

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Permeability – Lightweight slurries

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– Reaction to magnesium and sodium sulfates

Cement Slurry Properties

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Slurry density Slurry rheology Free water Thickening time Compressive strength Fluid loss control Compatibility

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• • • • • • •

Testing Process LAB ANALYSIS REQUEST SLURRY DENSITY

CEMENT - SPACER - MUD COMPATABILITY

FLUID LOSS TEST THICKENING TIME TEST

COMPRESSIVE STRENGTH TEST

LABORATORY REPORT 75

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FREE WATER TEST

RHEOLOGY

Laboratory Testing Equipment Waring Blender - Slurry Mixing Please Note:

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A Waring Blender imparts much more mixing energy than is experience in the field with standard cement mixing equipment and thus does not truly simulate field mixing conditions.

Well Conditions PROBLEM

SLURRY PARAMETER DENSITY

TEMPERATURE

THICKENING TIME

PERMEABLE FORMATIONS

FLUID STABILITY FLUID LOSS CONTROL

MUD REMOVAL FRICTION PRESSURE MIXABILITY/PUMPABILITY

RHEOLOGY

LOST CIRCULATION

PLUGGING BRIDGING PROPERTIES DENSITY

EXTENTERS WEIGHTING AGENTS ACCELERATORS RETARDERS FLAC DISPERSANTS GELLING AGENTS LCM EXTENTERS

ABNORMAL AND SPECIAL CONDITION

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HEAT RETROGRESSION

HYDRATION PRODUCT

SILICA

FOAMERS

STABILIZED FOAM CAPABILITY

FOAMING AGENTS AND STABILIZERS

FOAM

FOAMING TENDENCY

ANTI-FOAM

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WELL CONTROL OVER PRESSURE WEAK FORMATION

ADDITIVE CATEGORY SOLUTIONS

Slurry Density Lighter

•Absorbent •Light Material

Lower Density 78

Neat Cement 15.6 ppg Class A 15.8 ppg Class G 16.4 ppg Class H

Heavier Less Water

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More Water*

Changing of slurry density

•Heavy Material •Dispersant

Higher Density

Laboratory Testing Equipment Pressurized Mud Balance - Density

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An absolute must at the rigsite and in the lab 79

Definition of Rheology Rheology is the science of flow and deformation of matter

will FLOW

Apply a force

SOLIDS

Apply a force 80

will BREAK

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FLUIDS

Applications of Rheology in Oilwell Cementing Operations Laboratory

CemCADETM Schlumberger Private

Mixability / Pumpability

Effective Mud Removal

HHP requirements

Rheological Parameters

Friction Pressures

Real Pressures

Rheology (high) – Pressure (high) – HHP (high) 81

Laminar Flow V=0 V max

 Sliding motion  Velocity at the wall = 0  Velocity is maximum at the centre  Vmax = 2 V  Where V = Average particle velocity 82

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V=0

Turbulent Flow DIRECTION OF FLOW Schlumberger Private

 Swirling motion  Average particle velocity is uniform throughout the pipe

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Dispersants

Change with dispersants Why dispersants? – Reduce viscosity and yield point – Turbulent flow easier to achieve (Clients like slurry in turbulent for liner) – Reduce friction pressures – Improve cement slurry mixability (lower Ty) – Reduced water slurries (density up to 18 lb/gal) – Improve efficiency of fluid loss control additives 84

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

Types of Dispersants

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Sulfonates • Sodium Polynapthalene Sulfonate (PNS) D065, D080 • Polymelamine Sulfonate (PMS) D145A • Aromatic polymer D065A, D080A • Organic polymer D604M, D604AM Lignosulfonates • Lignin Derivative/HydroxyCarboxylic Acid D081 • Hydroxy Carboxylic Acid D121

Laboratory Testing Equipment Rotational Viscometer - Rheology Torsion Spring

Rotor Bob Cup

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Inner Cylinder Bearing Shaft

Slurry Stability Free Water and Sedimentation Schlumberger Private

• Channelling • Incomplete fill-up

Free Water

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Free Water and Sedimentation

Effects of Free Water

• Incomplete fill-up

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• Channelling

Cement Properties •

Cement Slurry Properties;

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– Water Cement Ratio: • Defines the min and max boundaries of water content in slurry, – Minimum water content is the amount of mixing water per sack of cement that will result in a consistency of 30 Bc after 20 minutes at 80 deg F and 1 atm – The normal water content is the of amount of mixing water per sack of cement that will result in a consistency of 11 Bc at the end of the test. – The free water content is the amount of water that separates from a 250 ml sample of slurry after 2 hours – The maximum water content is the amount of mixing water per sack of cement that will result in 3.5 ml of free water • Exceeding the maximum ratio will cause pockets of free water to form and reduce the strength of set cement.

Anti Settling Additives • Anti Settling Additives reduce

• Compatible with all Cementing products and cement • No significant effects on slurry properties, except rheology • Temperature range: up to 300 deg F • Antisettling Agent D153: 0.1 - 1.5 % BWOC • Liquid Antisettling Agent D162: 0.005 - 0.025 gal/sk 90

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– Free water – Sedimentation

Thickening Time • Depending on BHCT Thickening Time can

– Accelerators to reduce TT – Retarders to extend TT

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be adjusted by:

Accelerators

I

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II

III

IV

V

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• Shorten stage I and II, accelerate stages III and IV hydration of main cement phases is increased plus change in C-S-H structure • Offset retarding effects of other additives

Retarders • Retarders extend pumping TT • Mechanism of action depends on:

• Theories of mechanism of action – – – – 93

Adsorption Precipitation Nucleation Complexation

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– Chemical nature of retarder – Chemical composition of cement

Laboratory Testing Equipment Consistometer - Slurry Thickening Time

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Atmospheric HPHT 94

Compressive Strength • Poor protection against lateral forces Overburden Pressure

Unstable System 95

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Stable System

Laboratory Testing Equipment Compressive Strength

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Fluid Loss in Cement Slurries • Definition

• Why cement slurry loses water – Differential pressure – Permeable medium (formation) – Water/cement ratio ? Hydration needs 97

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– Filtrate (aqueous solution) lost to the formation – Filter cake deposited at formation face – Cement particles left in annulus

Why Fluid Loss Control? • Maintain constant water-to-solid ratio Constant Density Desired Yield Thickening Time Compressive strength Rheology Constant Properties

• Avoid annular bridging or excessive pump pressure • Reduce formation damage 98

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– – – – – –

Mechanisms of FLAC

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Particle Plugging 99

Polymer Plugging

Dispersants with FLACs

WITHOUT DISPERSANT

FILTER CAKE

RANDOM PACKING

WITH DISPERSANT

ORDERED PACKING

HIGH PERMEABILITY LOW PERMEABILITY 100

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Mechanism of action • Disperse cement grains and improve packing reduce permeability

Laboratory Testing Equipment Filter Press - Fluid Loss

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HPHT 101

Low Pressure

Cement - Mud Contamination • Acceleration or retardation

• Reduction of hydraulic bond • Increase of filtrate loss • Change of rheological properties 102

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• Reduction of compressive strength

Speciality Additives

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Antifoam/ defoamer agents Bonding agents Expansive additives Gas migration control additives, etc. Thixotropic systems LCM

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• • • • • •

Lunch Break

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60 Minutes

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Primary and Remedial Cementing Calculations

Cementing Calculations We want to calculate:

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Slurry Volumes Sacks of cement required Displacement Volume Estimated Job time Correct Plug bumping Pressure

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• • • • •

Important Rule Cement slurries should always have density specified by API.

•

Density can only be changed by using the appropriate additive.

•

If water/solids ratio is not correct, may get :

•

–

High viscosity / unpumpable slurry.

–

Excessive free water.

If the cement composition and one of the properties are known, other two properties can be calculated

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•

Slurry Yield

1 sack of cement = 94lbs = 1 cubic foot Dry Cement absolute volume = 0.0382 gal/lb 1 sack of cement = 3.59 gal Class G cement slurry @ 15.8 ppg (1.9 SG) uses 44% mix water or 4.97 gal/sx 7.48 gallons = 1 cubic foot 108

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When water is added to dry cement the resulting Slurry normally has more volume than the original Sack of 94lbs based on a material balance calculation.

Bulk and Absolute Volumes Bulk Volume : The volume occupied by a certain weight of dry material including void spaces between solid particles.

1 Sack = 1 cubic foot (cu.ft) = 94 pounds

Absolute Volume : The volume occupied by the same weight of material, less the void spaces between particles.

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CEMENT

B

Bulk and Absolute Volumes Cement 1 drum = 1 cu.ft = 7.48 gal

Absolute Volume of Cement:

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A

A

7.48 gal – 3.89 gal = 3.59 gal

Air in pore spaces will be displaced by water

Water

B

A 3.89 gal

110

B

Slurry Yield Definition :

The volume of slurry produced when 1 sack of dry cement (and additives) are mixed with water

Unit:

cubic foot/sack

(cu.ft/sk)

1 Sack 1 cu.ft

4.97 Gal 0.66 cu.ft

CEMENT + AIR

+

WATER

1.15 cu.ft

=

Slurry Yield = 1.15 cu.ft / sk 111 10/12/2009

SLURRY

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Class G API mix

Mix Water Requirement Definition :

The amount of water needed to hydrate 1 sack of dry cement (and additives) to create a pumpable liquid

Unit:

gal/sack

1 Sack 1 cu.ft

CEMENT + AIR

4.97 Gal 0.66 cu.ft

+

WATER

1.15 cu.ft

=

Water Required = 4.97 gps 112 10/12/2009

SLURRY

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Class G API mix

Slurry Density Definition :

The weight of 1 gal of slurry

Unit:

lb/gal 1 Sack 1 cu.ft

CEMENT + AIR

4.97 Gal 0.66 cu.ft

+

WATER

1.15 cu.ft

=

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Class G API mix

SLURRY

1 gal of slurry will weight 15.8 pounds

Slurry Density = 15.80 ppg 113 10/12/2009

Calculations - Example 1 All calculations based on one sack of cement Note: Absolute volumes from Field Data Handbook, Page:700.005 •

Example: Class G cement mixed by API specifications

Class G

94

*

0.0382

= 3.59

H20 (44%) 41.36

*

1/8.33

= 4.97

Total

*

135.36

1. Density =

135.36 lb/sk 8.56 gal/sk

= 8.56 = 15.81 lb/gal 2. Yield =

8.56 gal/sk 7.48 gal/cu.ft

3. Water required = 4.97 gal/sk (from the table) 114 10/12/2009

= 1.144 cu.ft/sk

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Material Weight (lb) * Absolute Volume (gal/lb) = Volume (gal)

Calculations - Example 2 •

Class G, mix @ 15.5 ppg Material Weight (lb) * Absolute Volume (gal/lb) = Volume (gal) H20 Total

94 8.33X

*

0.0382

= 3.59

*

1/8.33

=X

94 + 8.33X *

Density = 15.5 ppg =

94 + 8.33X 3.59 + X Yield =

115 10/12/2009

= 3.59 + X

3.59 + 5.35 7.48

X = Water required = 5.35 gal/sk

= 1.195 cu.ft/sk

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Class G

Calculations - Example 3 •

Class G, mix with 5.05 gps of water requirement Material Weight (lb) * Absolute Volume (gal/lb) = Volume (gal) 94

*

0.0382

= 3.59

H20

42.07

*

1/8.33

= 5.05

Total

136.07

*

Density =

136.07 8.64

= 15.75 gal/sk

= 8.64

Yield =

8.64 7.48

Water required = 5.05 gal/sk (from the table) 116 10/12/2009

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Class G

= 1.16 cu.ft/sk

Calculations - Example 4 •

Class G, Given slurry yield – 1.06 cu.ft/sk Material Weight (lb) * Absolute Volume (gal/lb) = Volume (gal) H20 Total

94 8.33X

*

0.0382

= 3.59

*

1/8.33

=X

94 + 8.33X *

Yield = 1.06 cu.ft/sk =

3.59 + X 7.48

Density = 117 10/12/2009

= 3.59 + X

X = Water required = 4.34 gal/sk

94 + 8.33 * 4.34 3.59 + 4.34

= 16.41 ppg

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Class G

Calculations - Example 5 •

Class H, 3% S001. Mix by API Material Weight (lb) * Absolute Volume (gal/lb) = Volume (gal) *

0.0382

= 3.59

2.82

*

0.0687

= 0.194

H20

94 (0.38)

*

1/8.33

= 4.288

Total

132.54

S 001

Density =

94

= 8.072

132.54 8.072

= 16.42 ppg

Yield =

Water required = 4.288 gal/sk 118 10/12/2009

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Class H

8.072 7.48

= 1.079 cu.ft/sk

Additives Requiring Additional Water D020, Bentonite –

5.3% (BWOC) additional water for each 1% D20 added.

D024, Gilsonite –

1 gal additional water for each 25 lb D24 added.

–

0.286% (BWOC) additional water for each 1 % D30 added;

–

therefore 10% for 35% D30.

D031, Barite –

0.024 gal additional water for each 1 lb D31 added.

D042, Kolite –

1 gal additional water for each 25 lb D42 added.

D066, Silica Flour –

0.343% (BWOC) additional water for each 1 % D66 added;

–

therefore 12% for 35% D66.

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D030, Silica Sand

Calculations - Example 6 •

Class A, D020 – 2% BWOC. Mix by API * Abs. Volume (gal/lb) = Volume (gal)

Class A

*

0.0382

= 3.59

*

0.0454

= 0.085

H20

94[0.46+2(0.053)] *

1/8.33

= 6.384

Total

149.08

Density =

149.08 10.059

D 020

94 1.88

= 10.059

= 14.82 ppg

Yield =

Water required = 6.384 gal/sk 120 10/12/2009

10.059 7.48

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Material Weight (lb)

= 1.345 cu.ft/sk

Calculations - Example 7 •

Class G, D042 - 12.5 lb/sk, D020 – 4% BWOC. Mix @ 13.8 ppg * Abs. Volume (gal/lb) = Volume (gal)

Class G

94

*

0.0382

= 3.59

D 042

12.5

*

0.0925

= 1.156

3.76

*

0.0454

= 0.171

H20

8.33X

*

1/8.33

= X

Total

110.26 + 8.33X

D 020

Density = 13.8 ppg =

110.26 + 8.33X 4.917 + X Yield =

121 10/12/2009

= 4.917 + x

X = Water required = 7.75 gal/sk

4.917 + 7.75 = 1.69 cu.ft/sk 7.48

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Material Weight (lb)

Calculations - Example 8 •

Class H, D020 – 2% BWOC (Pre-hydrated). D030 – 35% BWOC. Mix by API *

Abs. Volume (gal/lb)

Class H

*

0.0382

= 3.59

*

0.0454

= 0.0854

*

0.0456

= 1.5002

*

1/8.33

= 10.2012

D 020 D 030

94 1.88 32.9

H20

94[0.38+8(0.053)+0.1]

Total

213.756

Density =

= 15.3768

213.756 15.3768

= 13.90 ppg

Yield =

Water required = 10.20 gal/sk 122 10/12/2009

= Volume (gal) Schlumberger Private

Material Weight (lb)

15.3768 7.48

= 2.056 cu.ft/sk

Calculations - Example 9 •

Class H, D600 – 2.0 gps. D080 – 0.3 gps. D801 – 0.2gps. Mix @ 16.5 ppg * Abs. Volume (gal/lb) = Volume (gal)

Class H

94

*

0.0382

= 3.59

D 600

17.09

*

0.117

= 2

D 080

3.08

*

0.0973

= 0.3

D 801

2

*

0.1

= 0.2

H20

8.33X

*

1/8.33

Total

116.17 +8.33X

Density = 16.5 ppg =

123 10/12/2009

= 6.09 + X

116.17 + 8.33X 6.09 + X Yield =

=X

6.09 + 1.92 7.48

X = Water required = 1.92 gal/sk

= 1.071 cu.ft/sk

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Material Weight (lb)

Slurry Volume Calculations (1)

124

Draw a diagram

Csg/Csg Annulus Displacement Volume

13⅜ 13 inch 68ppf

5000 ft OH/Csg Annulus

9⅝ inch 47ppf

Shoetrack

8500 ft

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A well requires the 9⅝ inch 47ppf casing at 8500 feet cemented to surface with neat Class G cement. Previous casing is 13 ⅜ inch 68ppf set at 5000 feet. There are two joints of casing between the Float Collar and Float Shoe and the open hole requires an excess of 21.4%. Bit size is 12¼ inch.

Slurry Volume Calculations (1) Vol 1 (Csg/Csg Ann) 5000 x 0.3354 =

1677 ft3

(8500 – 5000) x 0.3131 x 1.214 =

1330.4 ft3

Vol 3 (Shoetrack) 80 x 0.4110 =

32.9

Total Volume 3040 ft3

ft3

Vol 4 (Displ Vol) (8500 – 80) x 0.0732 =

616.3 bbls

Vol 5 (Sacks cement) 125

3040 ÷ 1.144 =

2657 sx

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Vol 2 (OH/Csg Ann)

Break

126

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15 Minutes

Slurry Volume Calculations (2 & 3) A well requires the 20 inch 94ppf well requires the 7 inch (2) A23ppf (3) casing cemented at 1500 feet liner cemented at

127

using an inner cement stinger made up from 5 inch 19.5ppf DP. The previous casing was a 30 inch, 1 inch wall conductor which was driven to 300 feet. There is no float collar only a float shoe and the hole seems large so a guestimate at volumes to bring the cement to surface is 150% on OH size. Slurry is Neat Class G.

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12,200 feet with an overlap inside the 9⅝ inch 47ppf of 150m using Class G cement + 35% Silica Flour at 16.55ppg. Previous casing is set at 10,500 feet. There are two joints of casing between the Float Collar and Float Shoe and the open hole requires an excess of 10%. Bit size is 8½ inch. Running tool to be used is 5” DP, 19.5 ppf.

Slurry Volume Calculations (2) 70.7 ft3

Vol 2 (OH/Csg Ann)

237.1 ft3

Vol 3 (Shoetrack)

17.7 ft3

Total Volume 326.1 ft3

Vol 4 (Displ Vol) 69.73 +177

= 260.9 bbls

Vol 5 (Sacks cement) 128

326.1 ÷ 1.38 =

236 sx

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Vol 1 (Csg/Csg Ann)

Balanced Cement Plugs

Draw a diagram

Displacement Volume

Balanced Steel Volume

Internal Plug Volume

External Plug Volume

Height with Pipe in place

Plug in place with pipe

129

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Set a 150m balanced cement plug in the open hole (12¼ inch) with the base at 3500m and the last casing set at 2800m using 5 inch 19.5ppf DP.

Balanced Plug Calculations Vol 1 (External plug) 150 x 3.281 x 0.682 = 335.6 ft3

49.1 ft3

150 x 3.281 x 0.09972 = Vol 3 (Steel displacement)

150 x 3.281 x 0.0366 = 18.0 ft3

Total Volume 402.7 ft3

Calc 4 (Plug Height) (18 ÷(0.682 + 0.09972)) + 150 x 3.281 =

515.2 feet (157m)

Vol 5 (Displacement) 130

(3500 – 157) x 3.281 x 0.01776 =

194.8 bbls

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Vol 2 (Internal plug)

131

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End of Day 1