8 - Stuck Pipe_PTM_Handout

8/22/2019 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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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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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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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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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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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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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


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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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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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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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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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Differential Pressure Sticking

Phyd

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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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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

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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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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.

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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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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

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Diff. Sticking Spotting Fluids

80

60

40

20

0 10 20 30 40 50

percent

probabilityofpipefreeing

soaking time (Hours)


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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)

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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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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

8 - Stuck Pipe_PTM_Handout

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