Squeeze Cementing
Aug 19, 2014
Squeeze Cementing
Squeeze Definition
The placement of a cement slurry under pressure against a permeable formation causing the slurry to dehydrate and create a cementitious seal across the formation face.
Reasons ForSqueeze Cementing
Repair primary cement job Channels Voids due to losses
Shut-off produced water Shut-off produced gas Repair casing leaks Abandon depleted zones Selective shut-off for water
injection Seal lost circulation zone Shut off fluid migration
Squeeze SlurryDesign
Considerations: Viscosity Thickening time Compressive strength Fluid loss control
Squeeze pressure Slurry volume
Primary Concerns
Squeeze Purpose Formation Types Establishing an Injection Rate Method of Squeezing Slurry Design Laboratory Testing Slurry Placement Reasons for Failure
Good Habits
Pre-Job Meeting Review Procedures Discuss Potential Problems Establish alternative Procedure
Good Record Keeping Pressure Times Densities, Rates and Volumes
Cement SlurryViscosity
Low viscosity. Entry into small fractures and
small cracks Slurries using dispersants
preferred High viscosity
Useful for cementing large voids (vugs)
Will not flow into narrow restrictions unless high pressure applied
High gel strength restricts movement of the slurry
Laboratory Testing
Thickening Time Always use Hesitation Squeeze
Schedule Simulate Batch Mixing Monitor Gelling Tendencies Monitor Settling Tendencies Modify API Schedule for Actual
Down Hole Conditions Continue Hesitation until Slurry
Sets
Laboratory Testing
Fluid Loss Use Test Procedure in BJ Lab
Manual Heat Slurry From Ambient
Above 200°F Condition in Pressurized
Consistometer or use Stirring Fluid Loss Cell
Thickening Time
Required job time plus reversal of excess cement
Temperature and pressure Higher than in primary cementing Use API squeeze schedules for
testing Shallow wells
Short times (2 - 3 hours) Use of accelerators
Deep wells and hesitation squeezes Long times (up to hours)
Compressive Strength
High compressive strength Withstand shocks from running
tools, drilling etc. To prevent cracking during re-
perforation Partially dehydrated cement
(filter cake) Will develop sufficient strength Not of primary concern
Fluid Loss Control
Low pressure squeeze Cement to fill all voids Minimum node build up
Important with permeable formations Very low permeability
200 ml/30 minutes Low / medium permeability
100 to 200 ml/30 minutes High permeability (>100 md)
25 to 100 ml/30 minutes
Fluid Loss Control (cont.)
High pressure squeeze Medium to high permeability
200 to 500 ml/30 minutes Fractured limestones, cement
travels large distance from wellbore, re-perforation difficult: High fluid loss rate
300 to 800 ml/30 minutes Lost circulation material beneficial Lead and tail (hesitate)
Lead 300 to 800 ml/ 30 min Tail <300 ml/30 minutes
CementNode
PrimaryCement
Formation
DehydratedCement
Casing
CementNodes
FLUID LOSS(P = 1,000 psi)
800 ml / 30 min
150 ml / 30 min
50 ml / 30 min
15 ml / 30 min6 inchCasing
Cement Node Formation
Rate Of Filter Cake Build Up
Permeability of the formation Low = slow leak off High = fast leak off
Differential pressure applied Time over which pressure is
applied Slurry fluid loss control
Low = slow dehydration
High = fast dehydration Low permeability and fluid loss can
give excessive job times High permeability and fluid loss
can cause bridges
Rate of Filter Cake Build Up (cont.)
For a constant differential pressure applied Rate of cement filter cake growth
for a 30 md formation is approximately twice that for a 300 md formation
For a given cement slurry, the time taken to form a filter cake of given thickness will double for a ten fold decrease in formation permeability
Filter Cake Permeability
Lower fluid loss = lower cake permeability = less solids filtered out of slurry
Fluid Loss Time to Form Permeability
(API) 2.0 in. Cake
Neat cement < 30 sec. ± 5.0 md300 cc < 4 min. ± 0.5 md25 cc > 4 hours ± 0.05 md
Filter cake growth is indirectly proportional to the cake's permeability
Filter Cake Permeability (cont.)
Squeeze pressure Increasing squeeze pressure
does not reduce the permeability of the filter cake
Flow of filtrate through a filter cake is proportional to the permeability of that cake Darcy's law
Flow rate through filter cake of given permeability is proportional to the differential pressure
Cement Slurry Volume
Dependent upon length of interval to be squeezed
For job convenience 10 to 20 barrels are prepared
Volume for high pressure squeezes should be minimized Fracture at low pump rate Keep pressure below fracture
propagation pressure
Cement Slurry Volume (cont.)
Rules of thumb: Cement volume should not
exceed capacity of treating string Use two sacks of cement per foot
of perforations If injection rate after break down
is 2.0 bpm or more: Minimum volume 100 sacks
If injection rate after break down is less than 2.0 bpm: Minimum volume 50 sacks
Planning
Establish Two-Rate Fluid Injection Profile
Determine Fracture Gradient Determine BHSqT Determine Top of Existing
Cement Determine Formation Pore
Pressure
Planning - Cont.
Determine Formation Fluid Characteristics
Calculate Hydrostatic Pressure Differential
Review Completion Records
“Gather Data Before Designing a Cement Slurry”
Injectivity
Viscosity must be manageable Channel repair may require
small cement particle sizes
Injection Testing
Use water, chemical flush or weak acid
Used to ensure all perforations are open
Helps to estimate slurry injection rate
Helps to estimate pressure for performing squeeze
Helps to estimate cement volume required
If injection is not achieved, an acid perforation wash should be performed under matrix conditions
Establishing An Injection
Pump at a Constant Slow Rate Increase rate to Obtain
Desired Cement Placement Rate
“Remember not to Exceed Fracture Gradient !”
Why Establish Injection Rate
To determine if and at what rate “BELOW THE FRACTURE GRADIENT” fluid can be placed against the formation.
Two Rate Injection
Lowest Rate at which the Formation will take Fluid
Minimum Rate needed to Displace Cement to the First Hesitation Always Establish with Clear Fluid Avoid using Mud
Variable
Affects Rate Choice
Thickening Time Packer Depth Slurry Volume Depth Workstring Size Casing Size
When Fracture Pressure Is
Unavoidable ! REMEMBER
You Will Damage the Formation You Will Increase the Difficulty of
getting a Satisfactory Job
The Key is to“BE CONSERVATIVE”
Proper Execution
High Injection Rate - Low Pump Pressure
High Pump Pressure - Low Injection Rates
Types OfInjection Rates
Loose Injection Rates High Rates Low Pressures
Tight Injection Rates Low Rates High Pressures
6 to 8 BPM0 - 200 PSI
0.25 - 0.5 BPM3500 - 4000 PSI
Loose Injection Tight Injection
Injection Rates And Pressures
Injection Rate Profile
From Chevron DTC
Caution
“ High injection rates with high pressures”
Almost Never Acceptable! Yields highly fractured formations
that require a large volume of cement slurry, before actually obtaining a squeeze.
Reasons For Failure
Non-Determination of Injection Rate
Slurry Design and Testing Slurry Placement Problems
Squeeze Cementing Methods
Principal methods: Squeeze packers Cement retainers Bradenhead
Modes of operation: Low pressure High pressure
Job procedures: Running squeeze Hesitation squeeze
Packer or RetainerSetting Depth
Determine from CBL Using tail pipe:
Minimum distance from top perforation is limited by tail pipe length
Do not set tool too close to top perforation: Communication in annulus above tool
can collapse casing Do not set packer too high (running
squeeze): Minimize contamination with mud or
other fluids Minimum 30 ft 75 feet above top
perforation
Retrievable Packers
Compression or tension set packers are used for squeeze cementing
Packer should have by-pass valve to: Allow fluid circulation when running in
hole Clean tool after job Allow reversing of excess cement slurry Prevent swabbing
Flexible, can set and release many times
Can run in tandem with retrievable bridge plugs Place sand on top of bridge plug
Viscous Pill
Mud
Mud
Packer
Spacer
Viscous Pill
Cement
Squeeze Through A Packer Balanced Plug
Method Spot viscous pill Pull to top of pill Spot cement and spacer as balanced plug Under displace (1 to 2 barrels) to ensure
flow out of the drill pipe
Mud
Mud
Viscous Pill
Cement
Mud
Packer
Spacer
Squeeze Through A Packer Balanced Plug
Method Pull out above top of cement (500 ft) Set the packer and squeeze cement When squeeze complete, unset the packer Reverse circulate any excess cement and
spacer out of hole
DrillableCement Retainer
Prevent back flow where no cement dehydration is expected (circulating squeeze into channels)
Used where high differential pressure may disturb the filter cake
Where communication with upper perforated zone makes use of packers risky
Multiple zones, isolates lower zone Allow further squeeze operations without
waiting on cement. Can be set closer to the perforations (Less
fluid injected ahead)
Mud
Mud
Retainer
Running Squeeze Method Through A
Cement Retainer Run in hole with retainer on wireline or
drill pipe Set retainer If wireline set, run in hole with drill pipe If run on drill pipe sting out from retainer
Viscous Pill
Mud
Mud
Cement
Retainer
Spacer
Running Squeeze Method Through A Cement
Retainer (cont.)
Circulate cement down to bottom of drill pipe
Sting into the retainer and squeeze cement
Cement
Viscous Pill
Mud
Mud
Cement
Retainer
Running Squeeze Method Through A Cement
Retainer (cont.)
Sting out from retainer and reverse circulate excess cement and spacer
Pull out of hole
Bullhead Squeeze Method
Casing Pump500 - 1000 psi
Casing Pump500 - 1000 psi
Cement
DisplacementFluid
Mud orDisplacementFluid
Pump cement with packer Set
Displace Mud into Formation
Hold Annulus Pressure
Apply Squeeze Pressure
Spotting Method
Casing Pump500 - 1000 psi
Sting out of tool Spot cement Stab with Packer Apply Casing Pressure Displace Cement Apply Squeeze Pressure
Bradenhead Squeeze Technique
Used when low pressure squeezing is practiced
Used where casing and surface equipment have sufficient burst resistance to withstand squeeze pressures
This is the most popular method due to its simplicity
Bradenhead Method
Spot Cement Pull Work String Close Annulus Apply Squeeze Pressure
Coiled Tubing Operations
(Through Tubing Squeezes)
Advantages Time Savings Cost Savings Pumping Flexibility Fluid Placement Reduced Formation Damage Safety
Coiled Tubing Applications
Well Stimulation Wireline and Production
Logging Perforating Squeeze Cementing Fill Cleanup Sand Consolidation
Cement Requirements for Coiled Tubing
Squeeze Fluid Loss
< 60 and > 30 cc’s/30 min. Compressive Strength
1000 psi in 12 Hrs. Thickening Time
6 - 8 Hours at BHTT Free Water
Zero cc’s at 45° Angle
Cement Requirements for Coiled Tubing
Squeeze (cont.) Rheologies
@ R.T. PV; 200 to 350 YP; 70 to 130
@ BHTT PV; 70 to 130 YP; 10 to 25
Nodes 0.75 to 1 inch Firm Cake
Mud Placement
Placement of Mud Pull Nozzle Up while
Pumping, to MaintainMud-Brine Interface10 - 15’ Above Nozzle
Pump 1 BBL. Excess
Locate Top of Mud Fluid Pac the Well Wash Out
Contaminated Mud Identify Top of Mud
Viscous Pill
Perforations
Brine Fluid
Cement Placementand Squeeze
Circulate in Cement Pull Nozzle Up while Pumping
Cement, to Maintain Cmt/MudInterface 100’ Above Nozzle
Cement Volume from Evaluation Log
Pull Nozzle Above Cement Close Annulus and Squeeze Squeeze Pressure at 1500 to
2000 psi above Reservoir Pressure and Hold for
40 Minutes
Viscous PillCement
Perforations
Fresh WaterBrine Fluid
ContaminatingThe Cement Pump contaminant and Lower the Nozzle to Displace 1 BBL of Cement per BBL of Contaminant
Contaminate 50’ into MudPull Nozzle up and Pump Contaminant at a Rate of 1 BBL per 2 - 3 BBL of Previously Contaminated Cement
Contaminant
Cement / Contaminant(50/50)
Dehydrated CementNodes
Mud / Contaminant(50/50)
DehydratedCement nodes
Mud, CementandContaminant
Viscous Pill
Reversing Out
Contaminated Cement to be Reversed out the Following Day or After Cement has Set
Jet with Fresh Water While Going Down 50’ Below the Original Mud Top
Reverse out and Pull Nozzle at a Rate to Circulate out 1 BBL per BBL pumped
Repeat Reverse out 2 more Times or Until Returns Cleanup
Evaluate with CET, Repeat if Necessary
If OK, Reperforate and Test
Low Pressure Squeeze Cementing
Bottom hole treating pressure maintained below fracture pressure
Aim to fill perforations and connected cavities with dehydrated cement
Cement volume is small Hydrostatic control is required to prevent
formation breakdown Use safety factor of 500 psi Low pump rates
Friction pressure is negligible Perforations must be clean and free of
mud or solids Cement nodes should be small
High PressureSqueeze Cementing
Bottom hole treating pressure is higher than fracture pressure
Fractures created at or close to perforations
Fluid ahead of cement is displaced into fracture
Cement slurry fills the fracture and any voids or connecting channels
Further applied pressure dehydrates the cement against fracture walls
When final squeeze pressure is applied all channels should be filled with cement filter cake
Extreme Losses
Sodium Silicate Pre-Flush (Flow-Guard) Pump CaCl Pad Pump Fresh Water Pad Pump Flow-Guard Pump Fresh Water Pad Pump Cement Design
One Possible Situation for “Neat” Cement Low fluid loss = good frac!
Use Caution with Sodium Silicate Across Pay Interval
Running Squeeze
Misconceptions Formation Locks-up at High Rates Final Squeeze Pressure Must be
Obtained at the Rate Induced During Injection
Better Term “Walking” or “Creeping”
More Applicable for Low Permeability Formations
Always Know the Location of the Cement Know the P between Cement &
Wellbore face
When To High Pressure Squeeze
Where voids and channels cement behind casing are not connected to the perforations
Where small cracks or micro-annuli allow passage of gas but will not take cement Application of Ultra Fine cements
Perforations are plugged or debris ahead of cement cannot be removed
High Pressure Squeezes (cont.)
Extent of the induced fracture is a function of pump rate
Slurry volume is dependent upon pump rate: High rate = large fracture Large fractures = large volumes
Minimum volumes should be used to allow perforation past cement where required
Drilling mud or low fluid loss fluids should not be pumped ahead
Use weak acid or water as a pre-flush
Related Fracture Theory
Location and orientation of created fracture cannot be controlled
Fractures occur in plane perpendicular to direction of least resistance
In most wells overburden is the principle stress, vertical fractures result. Fracturing pressure is less than
overburden In shallow wells (< 3000 ft)
horizontal fractures can occur Fracturing pressure is greater than
overburden
H2
H1
PF Over-burden
High Pressure Squeeze Fracture
Orientation Where fracture pressure is less
than over-burden pressure
PrimaryCement
CementFilter Cake Mud
Filtrate
Filtrate
Mud
VerticalFracture
DehydratedCement
Casing
Running Squeeze
Cement slurry pumped continuously until final squeeze pressure is achieved This may be above fracture pressure
When pumping is stopped, final squeeze pressure is maintained and monitored
Pressure drop due to filtrate leak off should be re-applied up to final squeeze pressure
Repeat procedure as necessary until pressure remains steady for several minutes
Volumes are large 10 to 100 barrels
Hesitation Squeeze
Only practical method for small volumes Intermittent application of pressure at low
rates 0.25 to 0.5 bpm
Each application of pressure is separated by a period of shut-down to allow for filtrate leak-off 10 to 20 minutes
Initial leak-off is high As cake builds up and applied pressure
increases, leak-off slows down As several hesitations are applied, the
difference between initial pressure and final pressure becomes smaller
2,400
2,000
1,600
1,200
800
400
00 20 40 60 80 100 120 140 160
Surf
ace
Pres
sure
, psi
Time, minutes
A
B C D
Hesitation Squeeze Pressure Behavior
A = Slurry mix-water leaks off B = No slurry mix-water filtrates
therefore squeeze is complete C = Pressure is bled off D = Final pressure test
Hesitation Squeeze Profile Loose Injection Rate
1 2 3 4
1000
2000
0
PRES
SUR
E
TIME in HOURS
Pump as slow as possible( 1/4 to 1/2 BPM )
Chevron DTC
Hesitation Squeeze ProfileTight Injection Rate
2000
1000
0 1 2TIME in HOURS
PRES
SUR
E
( 1/4 to 1/2 BPM )
Chevron DTC
Best Results
“Always Plan for a Hesitation Squeeze, But be prepared for a Running Squeeze”
CFL Two Slurry Method
Conventional Method Lead Slurry: Fluid Loss < 100 cc’s Tail Slurry: No Fluid Loss Control
Modified Method(Chevron DTC)
Lead Slurry: Mod. Fluid Loss - 300 to 500 cc’s
Tail Slurry: Fluid Loss < 100 cc’s More Specifics to follow...
CFL Slurry DesignModified Method
(Chevron DTC) Loose Injection
Lead Slurry Fluid Loss 300 to 500 cc’s Thickening Time
1 to 2.5 hours Free Water & Comp. Strength - N/A
Tail Slurry Fluid Loss < 100 cc’s Thickening Time
3 - 5 hours (Hesitation Schedule)
Free Water & Comp. Strength - N/A
Modified Method
Loose Injection Tight Injection
CFL Two Slurry Method LWL Single Slurry Method
Lead : 500. . . . . . 300 . . . . . 200. . . . . . . N.A. Tail : < 100. . . . . . .100 . . . . 100 . . . . . . . 100
Fluid Loss Control
Chevron DTC
Calculating Pressure to Reverse-Out
Always know what pressures are required to reverse-out.
Step 1: Calculate Differential Fluid Gradient, psi/ft
15.6 ppg x 0.052 = 0.8112 psi/ft ( Cement )10.0 ppg x 0.052 = 0.5200 psi/ft ( Comp Fluid )
0.2912 psi/ft Step II: Determine Tubing Fill
Factor, ft/bbl (decimal book) 2-3/8” 4.7 lbs/ft tubing = 258.65 ft/bbl of fill
Step III: Calculate Pressure to Reverse-Out, psi/bbl
ex: 258.65 ft/bbl x 0.2912 psi/ft = 75.3 psi/bbl**Multiple psi/bbl by the barrels
of slurry left in the tubing
Hesitation Squeeze
Final squeeze is achieved when the leak-off becomes negligible
For loose, permeable formations a first hesitation period of up to 30 minutes is not unreasonable
For tight low permeability formations a short first hesitation period of ± 5 minutes is sufficient
Hesitation Squeeze
(Chevron DTC)
Always Test on Hesitation Schedule
Hesitation Time Dictated by Pressure Build-up
Be Patient Use CFL Slurry Know the Location of the
Cement Never Over-Displace Determine Final Squeeze
Pressure from Injection Profile
Misconceptions of Squeeze Cementing
Cement slurry enters formation pore spaces
All perforations are open High pressure squeezes
create horizontal pancake High final pressure is required
to assure success Final squeeze pressure must
equal future working pressure
GeneralRecommendations
Ensure hole is junk free Ensure perforations are open
Acid wash if necessary Low pressure squeeze where
possible Use low fluid loss cement Cement volume should not exceed
string volume High final squeeze pressure is not
essential Batch mix cement Allow adequate time for cement to
set based on compressive strength data