Squeeze_Cementing.pdf
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Transcript of Squeeze_Cementing.pdf
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Squeeze Cementing
Forces cement slurry, under pressure, throughperforations or holes in the casing or liner.. Used to permanently block entry of undesirable fluids
to the wellbore or to fill channels behind the casing.Water production form watered out zones or leaks areWater production form watered out zones or leaks arecommon targets.
Also used to set cement packers to isolate sections ofthe annulus.
The cement plug must remain an effective seal fulltemperature, highest pressure and in contact with anyfluid from the well.
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Repair Cementing
Squeeze Cementing Shutting off watered-out perforation intervals Filling channels behind the pipe Covering pipe annuli that was never cemented Covering pipe annuli that was never cemented Setting cement packers
Partly copied from Arco Alaskapresentation.5/26/2010 2George E. King Engineering
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Treatment Execution
Execution of squeeze cementing operations infour basic steps:Wellbore preparationSlurry mixing and pumpingSlurry mixing and pumpingSqueezeRemoval of excess cement
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Squeeze Cementing channel repair
Objectives1. Locate the channel
2. Perforate into the channel
3. Inject cement and fill the channel3. Inject cement and fill the channel
Problems1. locating the channel
2. squeezing into the channel
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Channel Detection
Cement bond log Noise log? - leaks Segmented or radial bond log
Bond differences Bond differences Looking for patterns that represent channels
Block perforate and squeeze techniques
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Squeeze Types
Hesitation squeeze steady application of pressurethought by some to force cement in matrix mayonly help build size of dehydrated mass or nodethrough fluid loss of liquid from the cement slurry.
Actually what may be happening in some cases is Actually what may be happening in some cases isthat the wellbore is being restressed forming astress cage by solids from mud or cement wedginginto and bridging on the formation. This may allow1 to 5 lb/gal higher fluid gradient weight than initialfrac pressure of the formation.
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Squeeze Types
Suicide squeeze This squeezeperforates two spots high andlow and squeezes from the bottomtowards the top. There is a chance,if slurry volumes are too large, ofif slurry volumes are too large, ofcement spilling out of the upperperforations and sticking theisolation packer or retainer inthe well.
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Fluid Loss Control
Excessive fluid loss in the slurry can result in bridgingof tubulars by dehydrated cement.
Slurries with too little fluid loss can result ininsufficient buildup of filter cake on the formation(may also be a function of permeability and(may also be a function of permeability andpressure).
Fluid loss additives may be required to control fluidloss.
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Cement Node Buildup
Node with minimalintrusion into
Casing Formation
intrusion intowellbore
Primary cementsheath
Arco5/26/2010 10George E. King EngineeringGEKEngineering.com
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Rheology Controls
Cement slurries have higher viscosity than mostworkover fluids and this significantly reducesmaximum possible pump rate.
Rheology and stability tests are commonlyperformed:performed: At surface mixing temperatures, and At bottomhole static temperature BHST (caution make
sure mix water temperature is not higher than bottomhole temp.).
Slurries must stable to provide good rheologycharacteristics that are easily reproducible.
Arco5/26/2010 11George E. King EngineeringGEKEngineering.com
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Slurry Volume
Volume of slurry prepared depends on: Length of perforated interval Capacity of liner/casing or channel behind pipe Void areas behind the perforations Force that can be applied to the tubing Force that can be applied to the tubing Configuration of surface mixing / pumping equipment Use of cement plugs, pigs or darts (isolation devices)
Previous squeeze experience provides bestguidelines.
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Depth Control (with CT)
In cement squeezing, surface equipment notaccurate enough to position CT nozzle
Downhole reference point is generally required Methods of setting depth reference
Tagging bottom Tagging bottom inaccurate in wells with fill, but viable in certain conditions
Tagging completion restrictions tubing end locator (TEL) or tubing nipple locators (TNL) commonly used in squeeze cementing
Arco5/26/2010 13George E. King EngineeringGEKEngineering.com
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Cement Contamination Problems
Contamination can result in: Unpredictable slurry characteristics Reduced compressive strength of the set cement Incorrect placement due to change in slurry volume
To avoid contamination: To avoid contamination: Spacer fluid should isolate (ahead of/behind cement) Lines should be flushed each time a new fluid is pumped Mechanical separation of cement slurry using CT plugs
(darts or pigs)
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Reel Manifold Sampling Point andFlush Line
Circulating pressuresensor
To reel core and CTthrough reel isolationvalve
Reel manifoldvalves
From pump unit Flush lineto disposal
Sample point
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Cement Composition and Vol.
Low or high fluid loss? Depends on depth Volume of cement? depends on channel size
Often try several small squeezes. Pressure? Pressure?
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Squeeze Success?
Usually about 50% - but conditions makesuccess vary widely.
Increases when: circulation is possible through the channel, circulation is possible through the channel, Isolation is used fro cement injection, cement blending is pod mix, the operator is experienced.
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Cement Packer
Can isolate the annulus Water control Tubing repair or isolation Stabilizing tubing prior to milling window
Problems and considerations Floating the cement in the annulus there are ways! How long a cement column? - 50 to 300+ feet. Cement compositions for packers
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Cement Packer
Perforated annulus at or below point forpacker.
May need to perforate above top of packerwhen annulus is liquid filled.when annulus is liquid filled.
Displace cement from a straddle packer orpacker and plug (or retainer) into the annulus.
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Cement Placement With andWithout Retaining Platform
Stable cement column
Cement slurry fallsthrough less densefluids
Stable cement columnplaced over the platform
Cement platform
A retainer, mechanical plug, highly gelled mud pill (10 to 20 bbls) or a cement plug maybe used as the platform.
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Tool SelectionTool strings should generally be kept to a minimumConnector
required on all jobsCheck valves
cannot be used with reverse circulation of excess cement cannot be used with reverse circulation of excess cementDepth correlation
tubing end or nipple locators are commonly usedPlug catcher
catch and retrieve plugs ahead/behind cement slurryNozzles
developed to improve the slurry placement
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Cementing Nozzle Features
Pins to retainball within thenozzle Multiplenozzle
Multiplesmall-diameterradial ports
Large-diameter
port
Multiplesmall-diameterradial ports
Largediameterports
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Monitoring RecordingParameters
Pump unit
Coiled tubing Pressure, rate/volume, string
weight, depth and tubing OD andtubing cycles.
Pump unit Pressure, density andpump rate/volume
Slurry batch mixer Monitor density andvolume
Other tankage Monitor density andvolume
Annulus Monitorvolume anddensity of allfluids returnedand pumpedthrough theannulus. Recordpressure.
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Wellbore Preparation
Filtered sea-water or similar
at high rate Choke open
Wellbore cleanand packed establish leakoffrate.
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Laying In Cement Slurry
Choke open
Slurry pumped atmaximum rate
Nozzle pulled up 50 ftbelow cementinterface
Wellbore pack fluid
Spacer/fresh water
Cement slurry
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Placing Thixotropic Slurries
Choke closed, ifwellbore not fluidpacked, pump slowlydown annulus toprevent U-tubing
Slurry pumped atmaximum rate/pressure
allowed
Nozzle placedabove thief zone
Wellbore pack fluid
Cement slurry
Wellbore pack fluidHighly gelled mud or otherplatform usually neededexcept in severe fluid loss.
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Commencing Squeeze
Choke back returnsmonitoring pressureand volumes
Low rate continuouspumping or hesitation
Wellbore pack fluidNozzle pulled up>50 ft abovecement interface
Wellbore pack fluid
Cement slurry
Spacer/fresh water
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Completing Squeeze
Choke back returnsincreasing final squeezepressure
Displacement fluid pumpedat maximum rate/pressure
allowed
Nozzle movedcontinuously orfrequently
Wellbore pack fluid
Cement slurry
Spacer/fresh water
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Contaminating Excess Slurry
Returns choked tomaintain pressure onsqueezed zone
Contaminant pumpedat maximum
rate/pressure
Nozzle penetrates slurry ata rate which provides a50% mix of contaminant
Contaminated slurry
Cement slurry
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Reverse Circulating Excess Slurry
Open returnsfrom CT
Fluid pumped at maximumrate/pressure for allowable
differential (1500 psi)
Nozzle penetratescontaminated slurry at arate which provides a50% mix ofcontaminated slurry andpack fluid
Contaminated slurry
Wellbore pack fluid
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Reverse Circulating Live Slurry
Open returnsfrom CT
Fluid pumped at maximumrate/pressure for allowable
differential (1500 psi)
Nozzle penetratesslurry at a rate whichprovides a 50% mix
Wellbore pack fluid
Cement slurry
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Wellbore Circulated Clean
Returns choked tomaintain pressure onsqueezed zone
Fluid pumped atmaximum rate/pressure
Nozzle reciprocatedthrough treatmentzone to TD
Differential pressuremaintained againstsqueezed zone
Wellbore pack fluid
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Wellbore PreparationWellbore preparation operations includeSlick-line work, e.g. fitting dummy gas-lift mandrelsPressure test the production tubing annulusEstablish hang-up depth or TD using slick lineConfirm and correlate depths with CT and flag the tubingConfirm and correlate depths with CT and flag the tubingRemove fill from rat hole below perforated intervalPerform pretreatment perforation wash or acidizingPlace a stable platform for cement slurryEnsure wellbore fully loaded with filtered water (or
equivalent)
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Slurry Mixing and Pumping
Key points in the slurry mixing and pumping processincludeBatch mix and shear the slurryConduct job-site quality control testsConduct job-site quality control testsPrepare contaminant and spacer fluids as requiredConfirm CT depthLay in cement slurry following pumping schedule
When using thixotropic cementsDo not stop pumping while cement is inside the work stringPlace CT nozzle above thief zone and pump down production
tubing/CT annulus while squeezing the cementOverdisplace cement slurries out of the wellbore5/26/2010 34George E. King EngineeringGEKEngineering.com
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SqueezeDownhole generation of filter cake aided byperforming hesitation type squeezesFor example, 10 min at 1000 psi, 15 min at 1500 psi,
20 min at 2000 psi...
As fracture pressure exceededFilter cake prevents formation from fracturing
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Removal of Excess Cement
Efficient removal of excess cementCritical to timely completion of job
Achieved using several methods:Achieved using several methods:Reverse circulation of live cementCirculation of contaminated cementReverse circulation of contaminated cement
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Reverse Circulation of Live Cement
Reverse circulation of live cement slurry can beperformed ifDesigned slurry thickening time (including safety factor)Designed slurry thickening time (including safety factor)
allows for completion of the reversing phaseCT penetration rate controlled to effectively dilute the
slurry as it is removedMaximum density of reversed fluid is 10 lb/galReversing is continued until clean returns observed at
surface
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Rev. Circulation of ContaminatedCement
Contamination of excess cement is often necessary to:
Extend slurry thickening time allows cleanout operations to be completed safely
Allow cleanout operations to be delayed until cement nodeshave increased compressive strength
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Typical Cement SlurryContaminant CompositionTYPICAL CEMENT SLURRY CONTAMINANT
COMPOSITION
Borax/Bentonite 10 to 20 lb/bbl Bentonite 20 lb/bbl Borax 3 gal Cement Retarder Bio-Polymer Gel 1.5 lb/bbl Biozan gel
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Circulation of ContaminatedCement
Conventional circulation used when:Operating conditions cannot safely support reverse
circulation of excess slurry
Example:Example:Operations performed through 1-1/4-in. work strings cannot
employ reverse circulation techniquesReason: excessive friction pressure encountered
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Evaluation of SqueezeMethods used to evaluate depend on treatmentobjectives
Initial step in evaluation processConfirm condition of wellbore in the treatment zoneConfirm condition of wellbore in the treatment zone
If wellbore is obstructedDrilling/under-reaming may be required
Additional checkEnsure the rat hole is debris or cement free
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