17-Stuck Pipe Second

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Stuck Pipe

Mud properties

Case histories

Decision tree Exercises

&

Recommended practices

for

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61 Stuck pipe prevention& fishing operations

DRILLING MUD INHIBITION

An Inhibited drilling mud will not react with the formation once it has been drilled.

NON - INHIBITIVE

Fresh - water bentonite mud

Fresh - water lignosulphanate mud

Sea - water mud Calcium based mud Potassium mud Magnesium mud

Magnesium/Potassium mud

Polymer mud

Oil - based mud

FULLY INHIBITED

(ROT) Rule of Thumb:

The more inhibited the mud, the more stable the hole.

INCREASING INHIBITION INCREASING

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MUD DENSITY (MUD WEIGHT)

Mass per unit volume of the mud - commonly referred to as the mud weight. Mud density influences the hydrostatic head of the mud column.

Mud density is achieved by the solids in the mud. These solids are either added by the Mud Engineer or derived from the formation.

Controlling the mud density may help us combat tight hole problems due to:

I. Differential Sticking

II. Mobile Formations

III. Unconsolidated Formations

Iv. Reactive Formations

DENSITY

CHANGE INCREASE DECREASE

RESULT POTENTIAL PROBLEMS INCREASED OVERBALANCE DECREASED OVERBALANCE DIFFERENTIAL STICKING Lost circulation LOST  MOBILE FORMATIONS  GEOPRESSURED FORMATIONS  UNCONSOLIDATED FORMATIONS  INFLUX

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MARSH FUNNEL VISCOSITY

Viscosity is a measure of the resistance to the flow of a liquid and indicates the thickness of the mud.

Funnel viscosity allows us to monitor changes in the mud, but does not tell us the cause of these changes.

Viscosity results from the solids in the mud. Smaller solids resulting higher viscosity.

THE EFFECT OF FLOW RATE ON VISCOSITY AND YIELD POINT.

VISCOSITY

YI E L D P O INT

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THE EFFECT OF TEMPERATURE ON VISCOSITY.

TEMPERATURE

GEL STRENGTH

♦ Gel strength is a measure of the attractive forces between the solids in the mud when it is stationary.

♦ Gels are Important as they keep solids in the mud in suspension. ♦ Gel strength increases with time.

♦ Gel strength is a function of the amount of solids in the mud.

PROBLEMS CAUSED BY EXCESSIVE GEL STRENGTHS

I. Higher pump pressures required to break circulation. II. Higher pump pressures required to circulate the mud. Ill. Higher surge pressures lost circulation.

IV. Higher swab pressures influx & hole Instability

V. Increased difficulty in removing drilled solids from system. VI. Increased gas entrainment in the mud.

VIS

CO

S

IT

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RHEOLOGICAL MUD PROPERTIES

Rheology is the study of the flow of fluids.

PLASTIC VISCOSITY (PV)

A measure of the muds resistance to flow due to the quantity, size and shape of solids in the mud.

YIELD POINT (YP)

A measure of the muds resistance to flow due to the type of solids in the mud. The higher yields point the better of carrying capacity of the mud.

RHEOLOGY

RESULT INCREASE _DECREASE HIGHER SURGE/ SWAB PRESSURE

REDUCED HOLE

CHANGE FORMATION INSTABILITY INFLUX LOST CIRCULATION

REDUCTION IN

CUTTINGS

POTENTIAL PROBLEMS

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FLUID LOSS

CHANGE RESULT

THE FILTRATION PROPERTIES OF MUD.

FLUID LOSS

♦ A measure of the fluid lost from the mud to the formation.

♦ In order for fluid loss to occur a permeable formation la required.

FILTER CAKE (Wallcake)

Result from a build up of solid as filtration progresses. In general high fluid losses result in thick filter cakes. Nature of filter cake is Important

Ideal filter cake is:

A. THIN

Maximizing effective hole diameter. B. HARD

Ensuring that it stays in place. C. IMPERMEABLE

Preventing filtrate from the mud entering the formation. INCREASE INCREASED FILTER CAKE THICKNESS MORE FILTRATE ENTERS FORMATION FORMATION INSTABILITY DIFFERENTIAL STICKING POTENTIAL

PROBLEMS

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QUESTIONS FROM RIG TEAM

1- Is hole being adequately cleaned?

2- Is mud reacting with formation causing it to swell? 3- Are mobile formations encroaching on the hole? 4- Is hole size reduced?

5- Is differential sticking causing the problem?

6- Have cuttings or weighting material fallen out of the mud?

7- Is formation instability resulting from excessive surge/swab pressures?

RESPONSE FROM MUD ENGINEER

1- Check mud rheology.

2- Check fluid loss - is filtrate reacting with formation?

3- Check mud density - is mud weight sufficient to hold back formations ? 4- Check filter cake thickness.

5- Check mud density and tiller cake characteristics. 6 - Check mud rheology.

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TIME LAGS

ASSOCIATED WITH MUD TREATMENT

A. MUD ENGINEER RECOGNIZES PROBLEM. e.g.

INCREASED WATER LOSS DUE TO SALT CONTAMINATION OF FRESH WATER BASED MUD (N.B. REACTIVE SWELLING SHALE FORMATION ALSO EXPOSED IN OPEN HOLE SECTION).

B. MUD ENGINEER ASSESSES IMPLICATIONS OF PROBLEM WITH RESPECT TO FORMATIONS EXPOSED - (CONSULTS WITH MUD LOGGER).

C. MUD ENGINEER NOTIFIES DRILLING TEAM OF PROBLEM. D. Drilling TEAMS NOW ALERTED!!!

E. MUD ENGINEER ASSESSES SEVERITY OF PROBLEM AND RECOMMENDS TREATMENT.

F. MUD ENGINEER BEGINS TREATMENT. (DRILLING MAY HAVE TO STOP).

G. MUD ENGINEER MONITORS RETURNS FOR SIGNS OF IMPROVEMENT IN MUD SYSTEM.

H. IMPROVEMENTS MAY TAKE ALONG TIME. (INCREASED RISK OF HOLE PROBLEMS DURING THIS RECOVERY PERIOD).

I. MUD ENGINEER INFORMS DRILLING TEAM OF IMPROVED MUD CONDITION BUT STRESSES THAT TIME REQUIRED TO ASSESS THE EFFECT ON HOLE CONDITION.

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THE IDENTIFICATION OF HOLE PROBLEMS FROM MUD

CONDITION. #

1

While drilling 26" hole through a sand formation with a fresh water bentonite mud the driller reports the following:

— HIGH TORQUE.

— OVERPULL ON CONNECTIONS.

— LARGE AMOUNTS OF FILL AFTER CONNECTIONS. — BACK-FLOW FROM THE STRING ON CONNECTIONS.

— SPORADIC RETURNS AT THE SHAKERS.

Mud properties Programmed Actual Mud wt. 9.16 ppg 9.16 ppg M / F Vis 100 – 120 secs 80 secs Fluid loss Uncontrolled Uncontrolled

PH 10 – 11 9

Q

:

WHAT IS HAPPENING DOWNHOLE ?

ANSWER

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THE IDENTIFICATION OF HOLE PROBLEMS PROM MUD

CONDITION. #2

While drilling a gumbo clay with a fresh water bentonite mud in 17.5" hole the driller reports the following:

— HIGH TORQUE. — REDUCED R.O.P.

— HIGH DRAGS ON CONNECTION.

— GRADUALLY INCREASING CIRCULATION PRESSURE. ERRATIC FLOW RETURNS.

Mud properties Programmed Actual

Mud wt. 9.1 – 9.6 ppg 10.0 ppg M / F Vis 50 – 60 secs 85 secs Fluid loss Uncontrolled Uncontrolled 10 min Gel Less than 20 35

Q: WHAT IS HAPPENING DOWNHOLE ?

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THE IDENTIFICATION OF HOLE PROBLEMS FROM MUD

CONDITION #3

While drilling 8 1/2" hole with a salt carbonate mud through the sandstone reservoir section the driller notes the following:

— INCREASED TORQUE AND DRAGS ON CONNECTION, — CIRCULATION IS UNAFFECTED.

A clay stone formation is exposed below the 9 5/8" casing shoe.

Mud properties Programmed Actual

Mud wt. 10.3 ppg 10.8 ppg M /F Vis. 40 55 Fluid loss < 2 ml 8 ml Yield point 10 15 Gels 3/5 9/14 Chlorides 300 g/l 220 g / l

Q : What is happening downhole?

Answer

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Causes of Stuck pipe

&

Predicting

Objective

• To fresh our knowledge on the causes

&

Mechanisms of stuck

• To develop a logical approach to predict

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DIFFERENTIAL STICKING

1. Circulation...

2. Reciprocal pipe movement... 3. Torque...

4. Problem...in relation to... Problem usually occurs when pipe is...…….

KEY WORDS

IMPOSSIBLE STATIONARY HEALS RESTRICTED INCREASES TIME DETERIORATES UNAFFECTED UNABLE

GEOPRESSURED FORMATIONS

I. Circulation may be..……. ……...due to ...…………...entering the annulus.

2. Pipe movement may be..……….. due to ……….. 3. .Torque may...……

4. Problems occur due to formation pressure being ...than mud hydrostatic pressure. Problem is...………....to stabilize with time.

Problem can occur while.………..

KEY WORDS

HIGHER RESTRICTED UNUKELY

INCREASE PACKING OFF UNAFFECTED LIKELY DECREASE LOWER TRIPPING DRILLING CAVINGS

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REACTIVE FORMATIONS

1. Circulation may be affected due to hole ... 2. Pipe movement may be...

3. Rotation may be possible but with gradual higher …………as hole size...………

4. When initially penetrated formation may not cause problems. A time delay may occur as...………..progresses.

Problems can occur while...………

KEY WORDS

SWELLING TRIPPING & DRILLING REDUCES INCREASES RESTRICTION DRILLING LIMITED TRIPPING TORQUE

UNCONSOLIDATED FORMATIONS

1. Pump pressure may……… indicating bridging or packing off.

2. Upward pipe movement may be………will cure this. 3. Downward pipe movement may be restricted. In this

case...or...side build up may have occurred and a...may be necessary.

4. Torque may be...……..., but may improve with....………….. Problem can occur while...……...

KEYWORDS

ERRATIC RESTRICTED SMOOTH

INCREASE DRILLING FILL

TRIPPING HIGH CIRCULATION

LOW DECREASE ROTAT1NG

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MOBILE FORMATION

1. If formation encroachment is severe. Circulation may be...………. 2. Up and down movement may both be. ……….

3. Rotation may be...but with ………..torque. 4. There is often a...delay before these formation ……… into the wellbore.

Problem can occur while ………..

KEY WORDS

IMPOSSIBLE LIMITED HIGH UNRESTRICTED UNAFFECTED TIME POSSIBLE DRILLING &TRIPPING

Flow Drilling Restricted Low

FRACTURED/FAULTED FORMATIONS

I. Circulation may be affected due to..……….

2. Overpull and drag will increase due to ...load. 3. .Rotation may be possible but with higher ... 4. Problems are likely to occur as the formation is drilled. ….. ....is paramount

and drilling ahead must take second place. With time the formation may...,... Problem can occur while..………...

1B

KEYWORDS

HOLE CLEANlNG

BRIDGING

FRACTURING

ERRATIC

STABSLIZE

TORQUE

CIRCULATION

INCREASED

TRIPPING & DRllLING

DRILLING

TRIPPING

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KEYSEATING

1. Clrculation...

2. ………...movement restricted.

3. Rotation may be... 4. A keyseat will...with time.

Problem usually manifests itself while tripping ……….

KEYWORDS

UNLIKELY HEAL UPWARD REDUCED RESTRICTED IMPOSSlBLE

WORSEN INCREASED LOST DOWNWARD UNAFFECTED FLUID

OUT IN POSSIBLE

WELLBORE GEOMETRY

1. Circulation usually ..………..

2. Overpull and drag likely to be...as opposed to a gradual increase. 3. Rotation may be possible but with. ………torque.

4. Problems tend to be mechanical (i.e ledging, doglegs) and are a result of the hole profile. It is...………...that the condition will stabilize with time. Other problems such as .……...can develop with time.

Problem can occur during...………

KEYWORDS

UNLIKELY UNRESTRICTED LIKELY SWELLING ERRATIC LOW RESTRICTED KEY SEATING HIGH

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DRILLED UNDERGAUGE HOLE

1. Circulation likely to be………...but may depend on new bit profile. 2. ....………...movement impossible.

Upward movement may also be impossible and as such the correct course of action would be to immediately. ………..

3. Rotation will be ……… ...If bit is jammed in undergauge hole. 4. The problem is...………by time.

Problem can occur during...………..

KEY WORDS

IMPOSSSBLE UNRESTRSCTED JAR UP DOWNWARD JAR DOWN UPWARD UNAFFECTED RESTRICTED POSSIBLE

TRIPPING DRILING TRIPPSNG & DRILLING

INADEQUATE HOLE CLEANING

1. Unless packing off occurs, circulation may be ………. 2. Both up and down pipe movement may be... Drag and overpull.

will reduce when...……….. 3. Rotation likely to be possible but

with...………and...………...torque.

4. Unless remedial action is taken the problem will ………....with time. Problem can occur during.………..

KEY WORDS DETERIORATE RESTRICTED UNRESTRICTED HIGHER IMPROVE PUMPING ERRATIC TRIPPING SMOOTH DRILLING LOWER

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JUNK

1. Circulation likely to be.………..

2. Restrictions to up and down movement are likely to be....……… 3. Rotation may be possible but torque likely to be ……… 4. Problem ..………with time.

Problem can occur during……….

KEY WORDS DETERIORATES RESTRICTED UNRESTRICTED POSSIBLE GRADUAL ERRATIC UNAFFECTED TRIPPING SMOOTH DRILLING IMPOSSIBLE TRlPPING & DRILLING

CEMENT BLOCKS

1. Circulation likely to be..……….

2. Pipe movement up and down may be……….. 3. Torque likely to be... and....………...

4. Problem may...………...with time if cement blocks cease to fall into the hole.

Problem can occur during.………

KEY WORDS

DETERIORATE RESTRICTED UNRESTRICTED HIGH STABILIZE ERRATIC LOW TRIPPING SMOOTH DRILLING IMPOSSIBLE TRlPPING & DRILLING

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79 Stuck pipe prevention

GREEN CEMENT

1. Circulation may be....………depending on cement condition.

2. Up and down pipe movement...…………possible but deteriorates rapidly. 3. Rotation may be possible but torque will………as cement... 4. Problem will deteriorate………... with time.

Problem can occur during..………..

KEY WORDS

INITIALLY POSSIBLE SETS SLOWLY INCREASE DECREASE ERRATIC FLOWS RAPIDLY TRIPPING DRILLING TRIPPING& DRILLING

Collapsed Casing

1- Circulation ………

2- Up and down pipe movement may be restricted depending on how much the casing I.D.is ………

3- If the casing is jammed and rotation is impossible ……… should commence immediately.

4- The casing I.D. may reduce with time as formation ……… continues Problem can occur during ……….

Key Words

Jarring Unrestricted Squeezing

Increasing Circulation Reduced

Fracturing Restricted Impossible

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DECISION TREE EXERCISES

WHEN DRILLING - PIPE STUCK WHEN PICKING UP

AFTER CONNECTION

DRAG TREND HAS BEEN INCREASING

CIRCULATION IS NOT RESTRICTED

( FULL RETURNS)

PERMEABLE FORMATION SUSPECTED

CANNOT MOVE STRING UP OR DOWN

CANNOT ROTATE STRING

PROBLEM?

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TRIPPING IN – WEIGHT INDICATOR SHOWS SUDDEN LOSS OF WEIGHT UPWARD PULL SHOWS EXCESSIVE DRAG

WITH KELLY ON – PUMP PRESSURE INCREASES DRAMATICALLY CAN JAR UP, BUT CANNOT JAR DOWN, CANNOT ROTATE

PROBLEM?

WHILE TRIPPING IN – WEIGHT INDICATOR SHOWS

SUDDEN ERRATIC LOSS OF WEIGHT.

UPWARD PULL SHOWS EXCESSIVE DRAG

PREVIOUS BIT WAS NOT GAUGED

DEVIATED DOG LEG NEEDS TO BE SURVEYED ON

THIS TRIP IN

BHA IS NOW 30 FT. LONGER THAN LAST BHA

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TRIPPING OUT - DRILLER NOTICED A LOT OF ERRATIC

AND OVERPULL, 20 STANDS OFF BOTTOM.

RELIEF DRILLER LEFT NO NOTES OF ANY PROBLEMS

IN THIS NEW HOLE SECTION.

WITHOUT CIRCULATION, DRILLER CANNOT GO UP OR

DOWN

DRILLER CAN ROTATE SLOWLY AND MOVE UP OR

DOWN

PROBLEM?

WHILE TRIPPING OUT - EXCESSIVE DRAG AND OVERPULL

LIMITED ROTATION (HIGH TORQUE)

CAN'T PULL UP OR DOWN

CIRCULATE IMPOSSIBLE

0B

WEIGHT INDICATOR LOSES WEIGHT WITH PUMP ON

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WHILE DRILLING – INCREASED TORQUE

NO CHANGE IN FORMATION SUSPECTED

SHORT TIME FOR BIT TO BE IN HOLE

EXCESSIVE HOLE DRAG NOTICED NO DOG LEG SUSPECTED PRESSURE TO CIRCULATE INCREASING.

DRAG REDUCES WHEN PUMPING FASTER.

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RECOMMENDED DRILLING PRACTICES

FOR THE

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GOOD DRILLING PRACTICES

• Always maintain circulation on connections for as

long as possible.

• Always maximize pipe motion when in open hole.

• Always begin pipe motion in a downward direction once

slips are pulled.

• If pump repairs are necessary stop drilling.

• Monitor and record the depths of higher torque.

• If hole conditions dictate Invest in wiper trips. These may

be to the casing shoe or only through newly drilled hole.

• Always monitor the shakers.

• Use top drives with care.

• Be prepared to limit penetration rate.

• On floaters use the motion compensator to minimize

sudden pipe movements.

• Always leave sufficient room on the kelly to allow jars to

operate.

• Never force the kelly bushings Into the rotary if fill is

encountered.

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GOOD TRIPPING PRACTICES

• Before tripping ensure that the shakers are clean. • Acknowledge increasing hole drags.

• Monitor and record the depths and magnitude of overpulls. • Never fight your way into or out of the hole - be patient. • If possible always use circulation to work the string through a tight

spot.

• Initially limit overpulls to half the drill collar weight below the jars. • Always insert slips when pipe is moving in a downward direction. • Swabbing indicates tight hole.

• In problem sections keeps the string moving in the slips. • Always ream at least the last three singles to bottom. • Minimize time spent in open hole.

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TIGHT HOLE MECHANISM

DIFFERENTIAL STICKING

*

Maximize string movement * Rotate string on connections.

* Always begin pipe motion in a downward direction. * Ensure pit space available for pumping pills.

* Use spiral D.C's.

* Minimize length of unstabilized D.C's. * Minimize length of B.H.A.

* Avoid surveying methods which result in pipe remaining static for long periods. * Consider using undergauge stabilizers in the drill string.

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GEOPRESSURED FORMATIONS

* Take time to clean the hole.

* Inspect the shakers for evidence of cavings. * If situation allows increase the mud weight. * Ream each single.

* Perform regular wiper trips.

* Observe pump pressure trends to identify annullus overloading. * Control rate of penetration.

* Minimize open hole time.

• Recognize increasing overpull trends and stop drilling until hole is clean. * Ensure mud specifications are maintained.

UNDERGAUGE HOLE

 Work/jar string upwards.

 Apply maximum forces from start of freeing operations.

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UNCONSOLIDATED FORMATIONS

 Be prepared when using a top drive system to ream during the stand.

 Control penetration rate.

 Use ALL solids removal equipment efficiently.

 Be prepared for shaker screen blinding.

 Clean out the hole before drilling ahead. Us viscous sweeps.  Avoid excessive periods of circulation opposite these formations.  Wipe each connection.

 Avoid excessive surge/swab pressures.

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MOBILE FORMATIONS

 If annulus packed off concentrate on establishing/ improving circulation.

 Work string by applying forces gradually.

 In the case of squeezing salt if circulation is possible spot freshwater mud while working the pipe. Do not delay in pumping water base mud . Water base mud should be large enough to cover stuck point with 20 bbls left in the string. In oil based systems pump a water/ detergent spacer ahead of the pill. Maintain maximum pull on the pipe while the pill is circulated. If pipe is not free in 2 hours repeat procedure.

 Key point

Remember well control implications.

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FRACTURED/FAULTED FORMATIONS

 Clean out excess fill before drilling ahead.

 Check condition of hole before drilling too far ahead.

 Clean out annulus at a slow, controlled rate (remember - lost

circulation potential)

 Minimize surge pressures restrict tripping speeds.

 Run a jar in the upper assembly.

 Be prepared to wash/ream when tripping in.

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REACTIVE FORMATIONS

KEY POINT

These formations result in packing off of the annulus

 Concentrate on establishing full circulation by working the string.

 Concentrate on downward working. Rotation may also help in disturbing the material packing off the annulus.

 Apply freeing forces gradually.

 If circulation is established an increase in mud weight may be beneficial.

WELLBORE GEOMETRY (PROFILE & LEDGES)

 Minimize doglegs to programmed limits.

 Minimize B.H.A. changes if possible.

 Anticipate reaming If B.H.A. configuration is changed.

 Whenever possible simplify B.H.A. configuration.

 Consider a hole opening trip.

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KEY SEATING

 Concentrate on working pipe upwards gradually. Avoid jamming string into key seat.

 Try to rotate string up and out of the key seat with minimum tension.

 If string reamer/key seat wiper installed attempt to remove key seat by back reaming.

 Minimize pipe rotation at the same point.  Wiper trips.

 Minimize dogleg severity.

 Consider BHA design / configuration.  Minimize length of rathole below casing.

 Consider in stalling a wiper or string reamer in the string if the problem is anticipated.



If problem recognized attempt to cure before drilling ahead.

KEY POINT

Immediate working required to reduce the risk of wall sticking.

JUNK

 Concentrate on upward and downward working/ jarring to dislodge the obstruction.

 Gradually increase applied freeing forces.  Only use equipment in good condition.  Inspect equipment regularly.

 Be careful when working around the rotary table.  Leave hole covered as long as possible.

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INADEQUATE HOLE CLEANING

 Ensure penetration rate is controlled to allow optimum hole cleaning.  Do not limit circulation to bottoms up. - Ensure shakers are clean.  Maintain check on cuttings volume changes at shakers.

 Maintain correct mud specifications.  Maintain programmed annular velocities.

 Recognize the significance of increasing overpull.  On semi submersible rigs use riser booster line.  Always reciprocate and rotate pipe while circulating.

 Select the optimum (recommended) viscous sweeps (directional / straight holes)

 Recognize the significance of hole deviation.

 Plan regular wiper trips.

Mobile formations

 Recognize the significance of reaction time associated with these formations.

 Regular wiper trips may be necessary.

 When tripping in slow down in advance and be prepared to ream.

 Condition mud prior to penetrating the formation.

 Consider the use of eccentric PDC bits.

 Consider increasing the mud weight if the situation allows.

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Green Cement

 Pre treat the mud if green cement suspected.

 Always know the theoretical top of cement.

 Begin circulation well above theoretical top of cement.

 Check for cement returns at the shakers

 Do not rely on the weight indicator.

 Restrict R.O.P. when cleaning out cement.

Cement blocks

 Minimize rathole below casing shoe.

 When drilling casing ratholes or cement plugs always ream section thoroughly before drilling ahead.