2 3 casing cementing

Cementing Technology• Lecture Contents: – Lecture Objectives,– Primary Cementing– Cement Classification,– Cement Additives,– Casing Hardware, – Cement Evaluation– Remedial Cementing Tech

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Cementing Technology

Cementing Technology

• Lecture Contents:

– Lecture Objectives,– Primary Cementing– Cement Classification,– Cement Additives,– Casing Hardware, – Cement Evaluation– Remedial Cementing Techniques

• Cement Plug

• Lecture Objectives:

At the end of this course, YOU will be able to:

• Understand the difference between primary and secondary

cementing,

• Identify classes of cement appropriate for different depth

range,

• Explain how the properties of cement may be altered by

the use of additives,

• Identify basic casing hardware and describe ways to assist

in the preparation of a cement job,

• Describe cement bond evaluation techniques

• Describe the remedial cementing techniques and calculate

the balanced plug,

Cementing Technology

Primary Cementing

• Introduction;

– Primary cementing is the introduction of cementacious

material into the annulus between casing and openhole to:

• Provide zonal isolation,

• Support axial load of casing string and other strings to be

run later,

• Provide casing protection,

• Support the borehole,

– Secondary/or Remedial jobs:

• Squeeze cementing,

Primary Cementing

• Thru-Drill Pipe Cementing;

• Key Points:

– Cement Contamination,– Channeling,

– Displacement,– Pump Until Slurry is at

surface.

uncemented (cement at TD and surface),

Liner Hanger

Liner Wiper Plug

Running Tool Shear Pin

Cement Classification

• API has identified classes for neat Portland cement.

• The criteria used by API is based on the degree of

the fineness of the cement particles.

• Class A:

– Intended for use from surface to 6000 ft, when

special properties are not required.

• Class B:

condition require moderate to high sulfate

Cement Classification

• Class C:

conditions require high early strength.

• Class D:

conditions of moderately high temperatures and pressures.

• Class E:

conditions of high temperatures and pressures.

Cement Classification

• Class F:

– Intended for use from 10000 to 14000 ft, under conditions of extremely high temperatures and pressures.

• Class G:

used with retarders and accelerators to cover a wide range of well depths and temperature.

• Class Geotherm:

– This is not an API, but it is basically a class G with

silica flour In order to withstand; high temperature,

Cement Classification

• Class H:

accelerated or retarded to cover a wide range of well depths and temperature.

• Class J:

16000 ft and can be accelerated or retarded

Cement Properties

• The properties vary according to the objectives

of the cement job Thus for casing job the cement must:

– Yield a slurry of given density while still exhibiting

desired slurry properties,

– Be easily mixed and pumped, – Meet optimum rheological properties required for mud

removal,

– Maintain both physical and chemical characteristics

during placement,

–

Cement Properties

• After Placement;

– Develop strength quickly, – Develop sufficient strength in the long term, – Develop casing and formation bond strength, – Have as low permeability as possible,

– Maintain quality even under severe temperature and

pressure.

Cement Properties

• The properties that are measured to determine a

particular job design are categorized as:

– Cement Slurry Properties, – Set Cement Properties.

• The properties of the cement will vary from one

well to another and will be determined by the characteristics of the well.

Cement Properties

• Cement Slurry Properties;

– Water Cement Ratio:

• Define the minimum and maximum boundaries of water

– The maximum being the water limit beyond which particles

will not remain in suspension until the cement has set The specification being 3.5 ml of free water after the cement has stood for 2 hours,

• Exceeding the maximum ratio will cause pockets of free

water to form and reduce the strength of set cement

• Higher density slurries may be obtained by using water content below the

minimum acceptable In such cases pumpability is achieved by using dispersants to increase fluidity

Cement Properties

• Cement Slurry Properties;

– Fluid Loss Control:

• Variation in water content will affect many characteristics such as

thickening time, rheology and compressive strength,

• Thus a neat slurry placed over a permeable formation will lose filtrate

resulting in dehydration of the slurry and decrease in the pumpability,

• Flash setting may occur due to rapid dehydration,

• Loss circulation may occur due to an increase in friction pressure,

• Final compressive strength maybe reduced due to lack of hydration

Cement Properties

• Cement Slurry Properties;

– Fluid Loss Control:

• Some typical fluid loss values are:

– For normal uncontrolled neat cement; 800/1000 ml/ 1000 psi

for 30 min,

– For cementing casing; 100/200 ml/ 1000 psi for 30 min,– For cementing liners; 50/100 ml/ 1000 psi for 30 min,

Cement Properties

• Cement Slurry Properties;

– Fluid Loss Control:

lower zone due to increased frictional losses;

Filtrate

Weak Zone

Filtrate Dehydrated Cement Fractured Weak Zone

Hydrostatic Pressure

Cement Properties

• Cement Slurry Properties;

– Slurry Rheology:

Velocity Profiles

Plug Laminar Turbulent

tend to maintain separation of different fluids,

laminar flow

Cement Properties

• Cement Slurry Properties;

– Pumping Time:

• Defines the time for which a slurry can be pumped,

• A slurry must be fluid for as long as it takes to place it and

then must set as soon as possible after pumping to limit the waiting on cement time,

• API defines the thickening time as the time for a slurry to

achieve 100 BC Cement operators normally assume a 50% contingency on pumping time to design their thickening time specification,

• Accelerators and retarders are used to increase or decrease a

slurries pumping time

Cement Properties

• Set Cement Properties;

– Compressive Strength;

• This property is required for:

– Securing and supporting the casing,– Withstanding the shock loading of drilling and perforating,

– Supporting hydraulic pressures without fracturing,– Withstanding the load of tectonic forces such as salt zone.

Unstable System

Overburden Pressure

Plastic Formation

Cement

Hydrostatic Pressure Casing

Cement Properties

• Set Cement Properties;

– Compressive Strength:

• Lab test proves that CS required to support casing is

normally less than 100 psi,

• 500 psi are required before drill-out cement,

• High CS are required to withstand hydraulic pressure

during injection and production operation,

• CS, typically increases with time as cement hardens, but

under conditions of high temperature, the CS may decrease

over a period of time, this is called STRENGTH

RETROGRESSION

Cement Properties

• Set Cement Properties;

– Cement Bonding;

• This is the main criteria for ensuring a seal Breakdown of

a the seal can occur due to shrinkage of the cement after hydration or cooling of the casing due to producing fluids,

• Micro annuli are formed which can be permeable enough

to allow gas migration,

• Therefore we can say that:

– The permeability of set cement and bond strength are both

properties that influence the isolation characteristics,

– Cement permeability normally is very low, 0.01 md, and

therefore is not a problem except in gas zone,

– High permeability can occur in extended cements and

therefore as general rule the water - cement ratio affects permeability of a cement

Cement Additives

• Cement additives can be classified as follows:

– Accelerators, – Retarders,

Cement Additives

• Accelerators;

– Accelerators generally work to decrease the thickening

time and build early compressive strength,

– Basically there are three types:

• Sodium chloride,

• Sea water

– Accelerators are used to reduce WOC, such as in surface

casing and shallow wells, particularly when low temperature is involved.

• NaCl, is not a very efficient accelerator and should be used

only when CaCl2 is not available,

• 10% will accelerate cement slurry, 20% will ac as a

– These are Chemicals used to delay cement setting time, in

order to allow enough time for proper slurry placement.

– Their main function is a fluid loss additives, by which they

maintain a constant water to solids ratio in cement slurries,

– They have the ability to retard cement.

Cement Additives

• Dispersants;

– These help maintain a uniform distribution of

components in a slurry and result in maintaining flow properties They are used to:

• Induce turbulent flow,

• Reduce water content and therefore increase the

compressive strength of the slurry, typically in plug jobs and can be used with adding weighting agents

• For fluid loss control.

Cement Additives

• Extenders;

– Extenders are used for one of the following reasons:

• Decrease slurry density to reduce the hydrostatic pressure

during cementing job,

• Increase slurry yield (cuft of slurry per sack of cement) and

hence decrease the overall cost,

– They are classified as following:

Cement Additives

• Weighting Agents;

– These are chemicals used to increase the cement slurry

density,

– They should meet the following requirements:

• High specific gravity,

• Larger particle size If small sizes, they increase viscosity,

• Low water absorption,

• Availability and acceptable cost.

– Examples of weighting agents are :

• Ilmenite (iron-titanium oxide)

• Hematite (iron oxide)

Cement Additives

• Lost Circulation Materials (LCM);

– They help to combat lost circulation They can do so by:

• Preventing the occurrence of induced fractures,

• Curing lost circulation by forming a low permeability

bridge across the opening,

– Some of the LCMs are:

• Granular,

• Flake,

• Fibrous.

• Defoaming:

– These are additives that remove foam from the cement slurry,

they could be found as antifoam or defoamer.

• Strength Retrogression Prevention Agents:

– Silica sand products are used to prevent such problem.

• Gas Channeling:

– This associated with the loss of hydrostatic pressure during

dehydration process

Casing Hardware

• Casing Shoe;

– Guide Shoe.

Casing Hardware

– Float Shoe;

FLEXIBLE LATCH PLUG

Casing Hardware

• Float Collar;

– To reduce contamination around the shoe, – 1-3 joints above shoe

Casing Hardware

• Float Collar;

– With Stab-in Ball Valve.

Casing Hardware

• Multiple Stage Cementer (DV);

– Conventional, – DV-Packer.

OPENING BOMB

CLOSING PLUG

Casing Hardware

• Wiper Plugs, Why?

– Separate Fluids, – Wiping casing, – Surface indication of placement.

Bottom Plug (Hollow Inside) Top Plug (Solid)

Casing Hardware

• Wiper Plugs;

– Non-Rotating Plugs.

Casing Hardware

• Casing Accessories;

– Basket & Centralizers

Centralizer Cementing Basket

Casing Hardware

• Casing Accessories;

– Centralizers

Casing Hardware

• Surface Equipment;

– Conventional Cement Head.

Cement Evaluation

classified in two broad categories:

– Flow problems of mechanical origin

– Degradation of the cement slurry

during the curing stage

Cement Evaluation

- Cement Evaluation Logs

Cement Bond Log (CBL)

Transmitter

3’ Receiver 5’ Receiver

Cement Evaluation

with the VDL waveform, has been for many years the primary way to

evaluate cement quality

The principle of measurement is to record the transit time and

attenuation of an acoustic wave after propagation through the borehole fluid and casing wall.

Cement Evaluation

TOC

Cement Evaluation

VDL

Cement Evaluation

CBL / VDL

TOC ?

Cement Evaluation

– A newer generation tool that is lighter

and more flexible for use in deviated holes The principle of the

measurement consists of recording two sets of receiver amplitudes and

computing their ratio This ratio is then used to compute attenuation.

resolution.

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Remedial Cementing

Remedial Cementing Technique

• Cement Plugs;

– A cement plug involves a relatively small volume of

cement slurry, and is placed in the wellbore for various purpose:

• To cure lost circulation during drilling,

• Directional drilling and sidetracking or whipstocking,

• To plug back a depleted zone,

• Abandonment,

• To provide an anchor for openhole tests.

• Cement Plugs;

– Applications;

• Sidetracking & Directional Drilling

Remedial Cementing Technique

Kick Off Point

New Hole

CEMENT PLUG

• Cement Plugs;

– Applications

• Plugback & Depleted Zone.

Remedial Cementing Technique

Depleted Zone

Cement Plug

CEMENT PLUG

CEMENT PLUG

CEMENT PLUG

Remedial Cementing Technique

• Cement Plugs;

• There are two Common Techniques for Placement Cement

Plug namely:

– Dump bailer,

– Balanced Plug.

• Cement Plugs;

– Placement Techniques;

• Dump Bailer:

– The tool is run with wireline and allows the placement of a measured quantity of cement,

– The dump bailer is opened as soon as it touches a permanent bridge plug The cement is dumped as the tool is pulled,

– Usually employed for setting plugs at shallow depths,

– Used for workover operations as the depth is easily controlled.

Remedial Cementing Technique

• Cement Plugs;

– Placement Techniques;

drillpipe or tubing to the desired depth,

to avoid mud contamination and proper placement,

hydrostatic balance,

flow back onto the rig floor,

the hole and the excess cement is circulated out

Remedial Cementing Technique

Fluid

Space r

Cement Slurry

• Cement Plugs;

– Placement Techniques;

Remedial Cementing Technique

• Slurry volume calculation.

• Cement Plugs;

– Placement Techniques;

• Slurry volume calculation

Remedial Cementing Technique

–Volume of Cement Vcmt Vcmt = L x Ch x S.F

L = Length of column of cement in openhole (ft),

Ch = Openhole capacity (ft3/ft)

–Length of Balanced Plug with String in Place Lcmt, Lcmt = Vcmt / (Can + Ctbg ), Can = Annular capacity between pipe and openhole (ft3/ft).

Ctbg = Capacity of pipe or tbg (ft3/ft).

• Cement Plugs;

– Placement Techniques;

• Slurry volume calculation

Remedial Cementing Technique

–Volume of Spacer behind the Cement.V sp2

Vsp2 = ( Vsp1 / Can ) x Ctbg

V sp1 = Volume of spacer ahead cement Slurry (ft 3 )

L = Length of column of cement in openhole (ft), –Length of Spacer Behind the Cement L sp2

Remedial Cementing Technique

• Squeeze Cementing;

– Purpose of Squeeze Cementing:

or insufficient height in the annulus,

hydrocarbon producing zone,

oil intervals,

injection well,

• Squeeze Cementing;

– Theory:

• The overall theory is due to the filtration process which include:

– How much differential pressure applied,

– Porosity and permeability of the interested zone,

– Filter cake deposition.

Remedial Cementing Technique

cement nodes

CEMENT

FORMATION DEHYDRATED CEMENT

• Squeeze Cementing;

• Placement:

– Low pressure,– High pressure

– Running,– Hesitation

– Bradenhead,– Squeeze tool

Remedial Cementing Technique

• Squeeze Cementing;

• Low pressure squeeze:

– Squeeze pressure below fracture,– Small slurry volume.

• High pressure squeeze:

– Squeeze pressure above fracture,– Large slurry volume.

Remedial Cementing Technique

• Squeeze Cementing;

– Running Squeeze;

• Continuous pumping,

• Final squeeze pressure attained,

• Large slurry volume,

• Low or high pressure squeeze.

Remedial Cementing Technique

• Squeeze Cementing;

– Running Hesitation Squeeze;

• Intermittent pumping,

• Low pumprate,

• High initial leak-off,

• Small slurry volume,

• Long job time

Remedial Cementing Technique