5 - casing cementing
TRANSCRIPT
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Casing Cementing
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• Lecture Contents:
– Lecture Objectives,
– Primary Cementing,
– Cement Classifications,
– Cement Additives,
– Casing Hardware,
Casing Cementing
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• Lecture Objectives:
– At the end of this lecture, YOU will be able to:
• Understand the difference between primary and secondary cementing jobs,
• Identify classes of cements 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.
Casing Cementing
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Casing Cementing– 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 against corrosion,
• Support the borehole,
– Secondary cementing or Remedial jobs:
• Squeeze cementing,
• Cement plug.
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Casing CementingPrimary Cementing;
• Conductor Pipe:
– Large excess required,
– Thru-drill pipe cementing common,
– BOP’s not unusually connected,
– Common Cements; Accelerated
– Top-Fill if necessary.
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Casing CementingPrimary Cementing;
• Thru-Drill Pipe Cementing (Stinger Cementation);– Key Points:
• Cement Contamination,
• Channeling,
• Displacement,
• Pump until Cement is at surface.
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Primary Cementing;
• Outside Cementing (Top-Fill);
– Purpose:• Bring Cement to Surface.
– Macaroni TBG used:• Max depth 250 - 300 ft,
• High friction Pressures,
• Only access via casing spool side outlet
Casing Cementing
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Primary Cementing;
• Surface Casing;
– Excess of 100%,
– Recommended thru-drillpipe method to save:
• Cement and Rig time.
– Common Cements:
• Lead light slurry with high yields,
• Neat tail slurries with good compressive strength,
• Reduce WOC to a minimum with accelerators.
Casing Cementing
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Casing CementingPrimary Cementing;
• Intermediate/Production Casing:
– Cemented to surface or into previous casing shoe,
– Two stage cement jobs may be required,
– Plugs, casing equipment and casing accessories are used,
– Require large cement volumes, excess of up to 50%.
• Common Cements:
– Typically filler slurries followed by high compressive tail,
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Casing CementingCasing String Components;
• Float Shoe or Guide Shoe:
– It is attached to the bottom casing joint,
– It serves as a guide for the casing as it is being run into the wellbore and acts as a one way valve.
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Casing String Components;• Float Collar:
– This is set about two-three joints above the casing shoe, and act as a one way valve,
– When it is used, the cement plugs land on top of it.
Casing Cementing
Ball Type
Flapper Type
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Casing CementingCementing Accessories:• Cementing Basket, to minimize losses in weak zones.• Centralizer, to centre casing in bore hole to promote
even distribution of cement around casing.
Centralizer Cementing Basket
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Casing CementingCementing Accessories;;
• Scratchers, to scratch offthe mud cake to improvecement bond
Reciprocating Scratcher
Rotating Scratcher
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Casing CementingCementing Hardware;
• Wiper Plugs:
– To Separate Fluids, (cement/chemical wash/mud)
– Wiping the casing clean,
– Surface indication of placement.
Bottom Plug (pump through) Top Plug (Solid)
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Casing Cementing
• Surface Equipment: Cement Head.
Double Plug Cement HeadSingle Plug Cement Head
Cementing Hardware;
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Formation Integrity Test (FIT)• Purpose:
– To investigate cement strength around the shoe (Cement Integrity Test),
– To approximate fracture gradient, (Leak Off Test),
– To investigate wellbore capability to withstand pressure below the shoe,
– To collect regional information on the formation strength for optimization of well design on future wells.
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Formation Integrity Test (FIT)• Test Procedure:
– Drill 5 to 10 ft below the last casing shoe,
– Circulate to condition mud (MW in = MW out),
– POOH to last casing shoe,
– Connect cement unit to test surface line,
– Close Pipe Rams,Start pumping at slow rate(i.e. 1/4 BPM) (A),
– While pumping, observe the pressure build-up until it deviates (B),
– Record pressure. (C),
– Bleed-off and record return.
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Formation Integrity Test (FIT)Leak-off or Cement Integrity Test procedure:
Pre
ssu
re
BBLSA
C
B
A-B: Linear Increase
B: Start of Leak-off
B -C: Mud Penetrating the formation
C: Leak-off pressure is reached
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Casing CementingPrimary Cementing;
Two Stage Cementing;
• Reasons to do: – Separation and isolation of zones,
– Reduces hydrostatic,
– Can leave zone in the annulus uncemented (cement at TD and surface),
– Loss zone.
STAGE COLLAR
FIR
ST
ST
AG
ES
EC
ON
D S
TA
GE
FLOAT COLLAR
FLOAT SHOE
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Casing CementingCasing String Components;
• Multiple Stage Cementer:
Running in Position Cementing Position Closed Position
OPENING
PLUG
CLOSING PLUG
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Casing String Components from bottom up;• Float shoe
– guide and check valve to prevent cement back flow• 3 Casing joints
– to capture any contaminated cement
• Float collar– second check valve– landing of bottom and top wiper plugs
• DV collar or Stage Collar (optional)• Centrilizers• Scratchers
– to remove mudcake and improve cement bond– to prevent / reduce cement channelling
Casing Cementing
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Primary Cementing
Primary Cementing;
• Liner cementation;– Run on liner hangers with Drill pipe
– Cemented to Top Of Liner (TOL)
– Drill pipe and liner wiper plug combination used
– Generally small volumes
Drill pipeWiper Plug
LinerHanger
Liner WiperPlug
Running Tool
Shear Pin
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Primary Cementing
Primary Cementing;
• Notes on Liner cementation;
– Liner-lap integrity is critical wrt isolation/sealing(200-400 ft)
– Small clearance between borehole and liner OD
– Incomplete removal of mud
– Liner riding on low side of borehole
Drill pipeWiper Plug
LinerHanger
Liner WiperPlug
Running Tool
Shear Pin
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Casing CementingSecondary Cementing; (Remedial job):
• Squeeze cementing– to squeeze off water layers
– to repair primary cementing jobs
NOTE: generally not effective:– risk of creating vertical fracs
– fluid losses and early setting of cement, (flash set)
• Cement plug– to abandon depleted zones
– to abandon well
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Casing CementingCement Classifications;
• API identifies classes and properties for cement:
A, B, C, D, E, F, G, H, J.
• The criteria used for the selection:
– downhole temperatures influence setting time
– slurry density in relation to drilled formations
– compatibility with formation (sulfate) waters
– rheological properties to displace mud
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Casing Cementing• Cement Properties:
– Be impermeable to gas, if present while setting.
– Develop strength quickly once it has been placed,
– Develop sufficient strength in the long term,
– Develop casing and formation bond strength,
– Have low permeability to prevent gas and fluid migration
– Maintain quality under severe temperature and pressure.
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Casing CementingCement Compressive Strength 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.
Overburden Pressure
Mobile Formation
Cement
Hydrostatic Pressure
Casing
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Casing Cementing• Cement 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 temperatures over 230 0F, the CS may
decrease over a period of time, this is called
STRENGTH RETROGRESSION.
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Casing CementingCement Additives;
• Accelerators:
– Accelerators generally work to decrease the thickening time and build early compressive strength, reduce WOC. (e.g. CaCl2).
• Retarders:
– These are chemicals used to delay cement setting time, in order to allow enough time for proper slurry placement, (e.g. Lignosulfonates).
• Dispersants:
– These help maintain a uniform distribution of components in a slurry and result in maintaining flow properties.
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Casing CementingCement Additives;
• Extenders:
– They are used to decrease the density and increase the volume, to prevent fractures. (e.g. Bentonite)
• Weighting Agents:
– These are chemicals used to increase the cement slurry density, to prevent kicks. (e.g. Barite)
• Lost Circulation Materials (LCM):
– They help to combat fluid loss, formation damage and to prevent losing water to prevent unwanted setting or no setting at all.
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• Demos:
Casing Cementing
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• Now YOU should be able to:
– Understand the difference between primary and secondary cementing jobs,
– Identify classes of cement appropriate for different applications,
– Explain how the properties of cement may be altered by the use of additives,
– Identify basic casing hardware.
– Describe the cementing process
Casing Cementing
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© COPYRIGHT 2002, NExT. All Rights Reserved
Casing Cementing
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