Download - 8 - Stuck Pipe_PTM_Handout
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SCOMI OILTOOLS
Global Research & Technology Centre/ GRTC
Training Department
STUCK PIPESTUCK PIPESTUCK PIPESTUCK PIPE
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Stuck Pipe
Stuck pipe is a long-standing problem in the drillingindustry.
It is estimated $200 - $500 million is spent annually as aresult of stuck pipe.
This amount could be drastically reduced bypreventative action and rapid response to keep minorsticking from developing into severe sticking.
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SCOMI OILTOOLS
Stuck Pipe Prevention
Communicate effectively
Plan ahead
Listen to the hole constantly
Maintain good mud
Keep the pipe moving
Clean out the hole as fast as you can drill it
Take action early
Stuck pipe is not inevitable
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Stuck Pipe Prevention
Operate BHA and string within limits
Keep the BHA as simple as possible
Run a drilling jar whenever possible
Whenever possible use spiral drill collars
Stabilize the BHA to minimise wall contact
Always gauge bits and stabilizers accurately
Bottom hole assemblies
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SCOMI OILTOOLS
Stuck Pipe Prevention
Failure to clean the hole
Monitor the hole for changes in drilling trends
Perform wiper trips as hole conditions dictate
Wipe/Ream the last stand before making a connection
Wipe the last stand or single before taking a survey
When drilling to casing point, calculate a target depth
Drilling
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Stuck Pipe Prevention
Plan the trip
Know the swab and surge pressures
Circulate clean prior to tripping
Ream and condition the hole while tripping in
Be careful while running with new bits
Tripping
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SCOMI OILTOOLS
Stuck Pipe Prevention
Ensure hole is clean & mud properties are in spec.
Calculate running speeds - do not exceed.
Centralize the casing string
Wash the casing through problem formations
Know the theoretical cement thickening time of cementbefore drilling out
When drilling cement establish circulation before drilling, drillwith low weight on bit.
Casing and Cementing
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Mechanism of Stuck Pipe
Formation related sticking
Mechanical sticking
Differential sticking
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SCOMI OILTOOLS9
STUCK PIPE
Formation Related Sticking
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Unconsolidated Formations
Usually encountered in top hole Loose sands Gravels Silts
Formation may collapse Indicators
Rough drilling Fill on trips Excessive drag & torque
Cavings Mud loss
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Unconsolidated Formation
Build low permeability filter cake
May require adjustments to rheology
Do not exceed flow rate required to clean the hole
Avoid rotating bits or stabilizers near problem area
Trip past problem area carefully
Clean out hole fill prior to drilling ahead
Consider soaking viscous pills into formation
XC Polymer/Bentonite/Fibrous LCM/Calcium Carbonate pills
w/- 10 minute soaking time
Stuck Pipe Prevention
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Unconsolidated Formations
If pipe is stuck due to formation collapse, circulation will belost.
Try to regain circulation while working the pipe downwards tobreak the bridge.
Once circulation is regained, clean the hole before drillingahead.
At this point, raising mud weight might be considered to
stabilize the hole.
Freeing stuck pipe
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Reactive Formations
Water sensitive clays absorb waterand swell and restrict the annulus Problem confined to WBM
Prevention Drill and case off quickly Choose suitable inhibitive mud and
mud weight. Monitor MBT closely Wipe hole regularly Prepare to dump and dilute
Freeing Use of drilling jar Once pipe is free, increase
inhibition levels and mud weight
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Fractured and Faulted Formations
Formations may give rise to ledges. May stabilize as wellbore collapses to
stable condition Risk of lost circulation and differential
stickingPrevention Circulate well before tripping Checking the hole during wiper trips Ream the hole on the way in Restrict tripping speeds and circulating
pressuresFreeing Work the pipe to break up pack-off/
obstruction In limestone, use inhibited HCl to
dissolve obstruction at stuck point
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SCOMI OILTOOLS
Mobile Formation
Formations that deform under pressure(salt and plastic shales)
Prevention Increased / Correct mud weight Ream while RIH Perform wiper trips Spot Freshwater pills Pump lubricants/base oil Use of eccentric PDC bits
Freeing (sticking in salt) Displace mud with freshwater until
drill collars/open hole annulus is filledwith water
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Geopressured Formations
Formations which pressured due to
loading pressures from the rock above
and below.
Signs
Pressure cavings (splintery) Hole enlargement Tight hole (due to hole cleaning
problems)
Prevention
Stabilize wellbore ASAP by
increasing mud weightFreeing
Increase mud weight Adjust rheology to improve hole
cleaning
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STUCK PIPE
Mechanical Sticking
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Undergauge Hole
Excessive bit wear
Jammed while RIH
Prevention
Always gauge bits
Trip carefully if known
Run gauge protected bits
Consider roller reamer
Jar upwards to free
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SCOMI OILTOOLS
Wellbore Geometry
Doglegs & Ledges
Often different BHA's will be less flexible and can get stuck.
Prevention
Minimise dogleg severity
Ream after BHA change
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Poor Hole Cleaning
Poor hole cleaning results inoverloading the annulus withcuttings, potentially sticking thedrillstring, accompanied by partialloss of circulation
This is most likely in washoutswhere annular velocity decreasesand cuttings accumulate.
In deviated wells, cuttings form beds
on the low side of the hole canmigrate up hole like shifting sanddunes.
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Good Hole Cleaning Practices
Clean the hole as fast as drilled
Ensure mud is within specification
Circulate clean prior to tripping
Reciprocate and rotate the pipe continuously
Plan and perform wiper trips as hole conditions dictate
Monitor the shakers
Keep all circulating and SRE in good working order
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Hole Cleaning Calculations
Calculate hole cleaning for the section with highestinclination.
Vertical Wells
High yield point Viscous mud High viscosity sweeps for large hole sections
Maintain adequate gels. Increase flow rate with hole angle 30o inclination requires 20% higher velocity 60o requires twice the AV of a vertical well
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SCOMI OILTOOLS
Hole Cleaning Calculations
Deviated Wells
High velocity
Use lower viscosity mud to induce turbulence
Clean cuttings beds with;
low viscosity pills followed by high viscosity, highweight pills (used with caution)
Rotation and reciprocation are critical > 45o
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Key Seating
Side ViewSide View Over Head ViewOver Head View
Extra hole made by action of pipe Originalrubbing against the formation Hole
Key Seat
Key seats
Grooves in the borehole wall cut by rotating drillpipe.
Not possible to pull drillpipe through the zone, but possible
to rotate.
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Key Seating
Prevention Drill with stiff BHA that tends to minimize chance o
severe doglegs
Use key seat wipers properly positioned in string
Freeing Apply downward force to drillstring
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Collapsed Casing
Formation forces exceed casingcollapse pressure
Casing is too light duty.
Casing is old.
Casing is landed with too muchtension or compaction reducingits collapse rating.
Casing shoe is poorly cementedand damaged during trips.
Casing joints come undone dueto poor make up and/or poorcement
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Junk
Parts of downhole equipment
Common inside casing
Prevention
Inspect all tools
Keep hole covered
Drillpipe wipers
Freeing
Work and jar the pipe
RIH to overgauge section
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Cement Related
Cement-related sticking
occurs when blocks of
cement fall into the
wellbore from casing
ratholes or cement plugs,
jamming the drillstring.
It also occurs when the
drillstring becomes plantedin soft or "green" cement
that flash sets when
pressure is applied.
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Differential Sticking
Criteria lead to diff. sticking: Hydrostatic pressure
exceeds formation pressure There exists zone of
permeable Thick filter cake is being
deposited There is contact between
pipe and wall This is the most preventable
type of sticking, sincecontact area, mud weightand filter cake can becontrolled.
POROUS
AND
PERMEABLE
ZONE
IMPERMEABLE
ZONE
IMPERMEABLE
ZONE
IMPERMEABLE
ZONE
IMPERMEABLE
ZONE
MUD
FILTRATE
MUD
FILTRATE
MUD
FILTRATE
Phyd
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Differential Pressure Sticking
IMPERMEABLE
ZONE
IMPERMEABLE
ZONE
POROUS
AND
PERMEABLE
ZONE
IMPERMEABLE
ZONE
IMPERMEABLE
ZONE
MUD FILTRATE
MUD FILTRATE
MUD FILTRATE
Phyd
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SCOMI OILTOOLS
Differential Pressure Sticking
Phyd
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Differential Sticking
Signs Increase torque and drag Fluid circulation unaffected Inability to move or rotate pipe
Prevention Maintain low fluid loss, thin filter cake, minimum contact area Use NAF mud better lubricity, thinner filter cake Alterations to location of stabilizers Use of friction coefficient reducers (lubricant)
Freeing Reduce hydrostatic pressure Use spotting fluids
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SCOMI OILTOOLS
Differential Sticking - Avoidance
Plan ahead
Contingency planning
Select BHAs with minimumcontact
Minimise mud weight
Have pit space available
Keep pipe moving andcirculate whenever possible
Continuously monitor pore
pressure
OverbalanceOverbalancepressurepressure MudMud
DrillpipeDrillpipe
FiltercakeFiltercake
SCOMI OILTOOLS
Differential Sticking
Probability of differentialsticking versus differentialpressure, established from
analysis of 600 well historiesin the gulf of Mexico.
An "acceptable" probability of20% is achieved if differential
pressure never exceeds 2000psi.
100
50
20
0
1 000 1 500 2 000 2 500 3 000
Differential pressure, psi
Stuckpipeprobability,
%
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SCOMI OILTOOLS
Differential Sticking
Three ways mudcake can be removed, diminishing theprobability of differential sticking :
While drilling, the rotating pipe wears one side of theborehole removing the cake.
During a wiper trip, the stabilisers and bit remove a largeportion of the cake. Reaming does the best job of removingcake, but it takes the most time.
Another method of removing filter cake is to use casingscratchers.
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Pipe Stuck Diagnoses
Drag trend increasing when
moving string from static
Is circulation restricted ?Are known
problem formations
exposed ?
Moving pipe from static after making/breaking connections
during drilling, tripping and reaming or after surveys
Y
Are permeable
formations
exposed ?
N
Reactive formations
fractured/faulted forms
mobile formations
unconsolidated forms
geopressured formations
Is drag reduced
when pumping ?
Y N Y N
Can drill string
be moved ?
Junk cement blocks string
component
failure stabilisers
hanging upon ledges
Reactive formations
fractured/faulted forms
mobile formations
unconsolidated forms
geopressured formations
Inadequate
hole cleaning
Y N
Y N
Junk cement blocks string
component
failure stabilisers
hanging upon ledges
Differential
sticking
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Spotting Fluids
These consist of a blend of surfactants and emulsifiersmixed in either a base oil or environmentally friendlyfluid.
The spotting fluid reduces the surface tension betweenthe well bore and the drill string, it also penetrates thewallcake promoting it's removal from the well bore.
The spotting fluid density should be slightly higherthan the mud to avoid migration, although someoperators prefer it lighter. In this case the loss of
hydrostatic head may be the important factor.
SCOMI OILTOOLS
Spotting Fluids
The success of spotting fluids depends on:
The volume displaced, the stuck point is located and sufficientpill is mixed up to cover all the pipe below this point. A 50%excess is normally mixed to cover for hole enlargement.
Proper placement. The pill is spotted across the stuck pointleaving 10 bbls in the drill string. 1/2 a bbl is then pumpedevery half hour while working the pipe.
The pill should be left for a minimum of 8 hours to soakbefore giving up. If pipe is not free after 40 hours consider
sidetracking.
The pill should be pumped as soon as possible after gettingstuck.
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Spotting Fluids
These are either supplied with emulsifiers for weightedsystems or without for non weighted systems.
Formulations depend on the supplier. Ensure an adequatesupply of spotting fluid is kept on the rig and formulation datais available for the required mud weights.
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Stuck Pipe Warning Sign
Fractured/faulted
formations
N
N
N
N
N
N
N
N
N
Y
Y
Y
YY
Y
Y
Y
Y
Y
N
Rotary Drilling
Increased Torque
Is there a formationchange ?
Increase in torquerelated to formation
change
Are bit hoursexcessive?Have abrasive
formations beendrilled ? If tri-cone bit bearings worn
Is circulation restricted?Can drag be
related todog legs
Have abrasiveformations been
drilled
Are drags reducedwhen pumping
Have problem formationsalready been exposed
Newly drilledGeopressured forms
unconsolidated formsfractured/faulted forms
fast movingmobile form
Is it possible thata fault has been
drilled ?WellboreGeometry
Cementblocksjunk
casingkeyseat
Inadequate hole
cleaningUndergauge hole
causingstabilizersto hang up
Have formations of
varying hardnessbeen drilled ?
Bit failurestring
componentfailure
Stabilizershanging up
on formationledges
Slow movingmobile
formationsreactive
formations
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SCOMI OILTOOLS
Differential Sticking
Select alternative freeing method
Is overbalance for
well control/wellbore stability
Differentially stuck
Is a Suitable PRA
available on site ?
Work/jar pipe
Is U -tubingpossible
Prepare PRA pill and spacerAgree procedure and prepare to U-tube
Use selective alternative
freeing method
Pump PRAU-Tube
Pipe freePipe free
U-Tube for second time
Pipe free
Continue operation -check low
gravity solids and fluid lossCut pipe and fish/sidetrack/
abandon
Worked Pipe free
YES
YES
NO
YESYES
YES
YES
YES
NO
NO
NO
NO
SCOMI OILTOOLS
Diff. Sticking Spotting Fluids
80
60
40
20
0 10 20 30 40 50
percent
probabilityofpipefreeing
soaking time (Hours)
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SCOMI OILTOOLS
Spotting Fluids Unweighted
BREAK-FREE NW Unique blend of surfactants and carrier fluid
Can be mixed in all types of non aqueous base fluids and glycols
Add 3 -4 gals of BREAK-FREE NW per bbl of base fluid
Other companies products:
Pipe-Lax (Miswaco)
Mil-Free(Baker Hughes)
Envirospot (Halliburton)
SCOMI OILTOOLS
Spotting Fluids Weighted
BREAK-FREE Blend of Surfactants, Emulsifiers and an Oil Soluble, Water
Emulsifiable Polymer
Used where a weighted pill is required.
Normal treatment level is 5 gal of BREAK-FREE per bbl offinished spotting fluid
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SCOMI OILTOOLS
Spotting Fluids Weighted
BREAK-FREERecommended Formulation - 100 bbl
Density
lb/gal
BREAK-
FREE
Base Fluid
(bbl)
Water
(bbl)
Barite
25 kg sacks
8 9 64 27 69
10 9 58 26 254
12 9 54 22 456
14 9 51 21 636
16 9 49 11 84618 9 44 10 1036