17-Stuck Pipe Second

             

Stuck Pipe Mud properties Case histories Decision tree Exercises &

Recommended practices for Prevention Stuck pipe

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

INCREASING SALINITY

Sea - water mud

INCREASING INHIBITION

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.

61 Stuck pipe prevention& fishing operations

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

RESULT

POTENTIAL PROBLEMS

INCREASE

INCREASED OVERBALANCE

DIFFERENTIAL STICKING Lost circulation LOST

DECREASE

DECREASED OVERBALANCE

 MOBILE FORMATIONS

 GEOPRESSURED FORMATIONS  UNCONSOLIDATED FORMATIONS  INFLUX

62 Stuck pipe prevention& fishing operations

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.

YIELD POINT

THE EFFECT OF FLOW RATE ON VISCOSITY AND YIELD POINT.

VISCOSITY

63 Stuck pipe prevention& fishing operations

VISCOSITY

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.

64 Stuck pipe prevention& fishing operations

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 CHANGE

RESULT

POTENTIAL PROBLEMS

INCREASE

HIGHER SURGE/ SWAB PRESSURE

FORMATION INSTABILITY INFLUX LOST CIRCULATION

DECREASE

REDUCTION IN CUTTINGS

REDUCED HOLE

65 Stuck pipe prevention& fishing operations

FLUID LOSS INCREASE

CHANGE

RESULT

INCREASED FILTER CAKE THICKNESS

POTENTIAL

DIFFERENTIAL STICKING

PROBLEMS

MORE FILTRATE ENTERS FORMATION

FORMATION INSTABILITY

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.

66 Stuck pipe prevention& fishing operations

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.

67 Stuck pipe prevention& fishing operations

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.

68 Stuck pipe prevention& fishing operations

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

69 Stuck pipe prevention& fishing operations

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 ? ANSWER

70 Stuck pipe prevention& fishing operations

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

71 Stuck pipe prevention& fishing operations

Causes of Stuck pipe & Predicting Objective • To fresh our knowledge on the causes & Mechanisms of stuck • To develop a logical approach to predict a potential stuck pipe situation

72 Stuck pipe prevention& fishing operations

DIFFERENTIAL STICKING 1. Circulation...................................... 2. Reciprocal pipe movement................................... 3. Torque............................................. 4. Problem............................in relation to............... Problem usually occurs when pipe is......…….

KEY WORDS HEALS TIME UNABLE

IMPOSSIBLE RESTRICTED DETERIORATES

STATIONARY INCREASES UNAFFECTED

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 INCREASE LIKELY TRIPPING

RESTRICTED PACKING OFF DECREASE DRILLING

UNUKELY UNAFFECTED LOWER CAVINGS

73 Stuck pipe prevention& fishing operations

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 INCREASES LIMITED

TRIPPING & DRILLING

REDUCES

RESTRICTION

DRILLING

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

PILL

DRILLING & TIRIPPING

TIME 74

Stuck pipe prevention& fishing operations

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

UNAFFECTED

TIME

Flow

HIGH

UNRESTRICTED

POSSIBLE

DRILLING &TRIPPING

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..………………......

KEYWORDS 1B

HOLE CLEANlNG

BRIDGING

ERRATIC CIRCULATION DRILLING

STABSLIZE INCREASED TRIPPING

FRACTURING TORQUE TRIPPING & DRllLING

75 Stuck pipe prevention& fishing operations

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

TRIPPING

DRILLING

TRIPPING & DRILLING 76

Stuck pipe prevention& fishing operations

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 UNRESTRICTED

IMPROVE

RESTRICTED

HIGHER

PUMPING

ERRATIC

SMOOTH

LOWER

TRIPPING

DRILLING

TRlPPING & DRILLING

77 Stuck pipe prevention& fishing operations

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 UNRESTRICTED

GRADUAL

RESTRICTED

POSSIBLE

ERRATIC

UNAFFECTED

SMOOTH

IMPOSSIBLE

TRIPPING

DRILLING

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 UNRESTRICTED

STABILIZE

RESTRICTED

HIGH

ERRATIC

LOW

SMOOTH

IMPOSSIBLE

TRIPPING

DRILLING

TRlPPING & DRILLING

78 Stuck pipe prevention& fishing operations

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 SETS DECREASE RAPIDLY TRIPPING& DRILLING

POSSIBLE INCREASE FLOWS DRILLING

INITIALLY SLOWLY ERRATIC TRIPPING

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

Tripping

Drilling

Tripping & drilling

79 Stuck pipe prevention

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?

80 Stuck pipe prevention

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 PROBLEM?

81 Stuck pipe prevention

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 WEIGHT INDICATOR LOSES WEIGHT WITH PUMP ON 0B

PROBLEM?

82 Stuck pipe prevention

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. PROBLEM?

83 Stuck pipe prevention

RECOMMENDED DRILLING PRACTICES FOR THE PREVENTION OF STUCK PIPE

84 Stuck pipe prevention

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. •

Always wipe the hole before making a connection.

85 Stuck pipe prevention

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.

•

Know how the jars work.

86 Stuck pipe prevention

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. * If necessary place the Jar in the heviwate drill pipe.

87 Stuck pipe prevention

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.

88 Stuck pipe prevention

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.  Be prepared for loose fiII when running to bottom.

89 Stuck pipe prevention

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.  If circulation is possible an increase in mud weight should be considered.

90 Stuck pipe prevention

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.  Design B.H.A. to minimize risk of ledge formation.

91 Stuck pipe prevention

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 dog- legs 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.  Do not run stabilizers above the jar.

92 Stuck pipe prevention

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.  Install drill pipe wiper on the hole whenever possible.

93 Stuck pipe prevention

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.  Minimize open hole time.

94 Stuck pipe prevention

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.  Beware when tripping back though the casing or past cement plugs.

95 Stuck pipe prevention