WELL PROBLEMSWELL PROBLEMS

WELL PROBLEMSWELL PROBLEMS

I.I. Well kicks.Well kicks.

II.II. Stuck pipeStuck pipe

III.III. Lost circulation.Lost circulation.

IV.IV. Restriction in the drilling string.Restriction in the drilling string.

V.V. Washout of the drilling string.Washout of the drilling string.

I.Well KicksI.Well KicksIt is the entering of the formation It is the entering of the formation

fluid to the wellbore.fluid to the wellbore.• this occur when the formation this occur when the formation

pressure exceeds the hydrostatic pressure exceeds the hydrostatic pressure.pressure.

• A blowout is uncontrolled kick.A blowout is uncontrolled kick.

Well KicksWell Kicks• Overbalance.Overbalance.• Underbalance.Underbalance.• Factors controlling the kicks sevirity:-Factors controlling the kicks sevirity:-

1. permeability.1. permeability.

2. underbalance.2. underbalance.

Reasons for KicksReasons for Kicks1.1. Insufficient Mud Weight.Insufficient Mud Weight.

2.2. Swabbing.Swabbing.

3.3. Gas cut mud.Gas cut mud.

4.4. Failure to keep the hole full.Failure to keep the hole full.

5.5. Lost circulation.Lost circulation.

11..Insufficient Mud WeightInsufficient Mud Weight..

The formation pressure is higher than the The formation pressure is higher than the hydrostatic pressure.hydrostatic pressure.

2.Swabbing2.Swabbing

A negative hydrostatic pressure A negative hydrostatic pressure causing reducing bottom hole causing reducing bottom hole

pressurepressure The speed of the drill pipe pulling.The speed of the drill pipe pulling. Mud flow properties; yp, gel.Mud flow properties; yp, gel. Hole geometry.Hole geometry. Balled up string.Balled up string.

3.Gas cut mud3.Gas cut mud

4.Failure to keep the hole full. 4.Failure to keep the hole full. 5.Lost circulation5.Lost circulation

Indications of KicksIndications of Kicks Changes in mud gas.Changes in mud gas. Drilling breaks.Drilling breaks. Improper hole fillups in trips.Improper hole fillups in trips. Pump pressure decrease and pump Pump pressure decrease and pump

strokes increasestrokes increase Flow out rate increase.Flow out rate increase. Pit Volume Increase.Pit Volume Increase. String weight change.String weight change. Well flowing with pumps off.Well flowing with pumps off.

WELL CONTROLWELL CONTROL

Early kick recognition & Early kick recognition & prompt execution of correct prompt execution of correct

shut-in procedures shut-in procedures isis the key the key to successful kick control.to successful kick control.

ObjectivesObjectives

1.1. Kell safely.Kell safely.

2.2. Minimize borehole stresses.Minimize borehole stresses.

A. Shut-in ProceduresA. Shut-in Procedures Hard Shut-in:Hard Shut-in:

the adjustable the adjustable choke is closed choke is closed before taking a kick.before taking a kick.

Soft Shut-in:Soft Shut-in:

the adjustable the adjustable choke is opened choke is opened before taking a kick.before taking a kick.

In order to kill a well the bottom In order to kill a well the bottom hole pressure must be maintained hole pressure must be maintained constant at a level greater than or constant at a level greater than or equal to the formation pressure.equal to the formation pressure.

B. U – tube TheoryB. U – tube Theory

1.1. No influx, no No influx, no Imposed pressure.Imposed pressure.

2.2. BHP =BHP = HP + IP + HP + IP + PLPL

BHP=5200+0+0=5200psiBHP=5200+0+0=5200psi

22 . .No Influx, with imposed pressureNo Influx, with imposed pressure

FP=HP+IP+PLFP=HP+IP+PL=5200+800+0=6000psi=5200+800+0=6000psi

33 . .No influx, Unbalanced tube sidesNo influx, Unbalanced tube sides..

FP=HP+IP+PLFP=HP+IP+PLFPdp=5200+0+0=5200psiFPdp=5200+0+0=5200psi

FPan=4680+520+0=5200psiFPan=4680+520+0=5200psi

44 . .Influx, Unbalanced tube sidesInflux, Unbalanced tube sides..

The drill pipe side is always used for The drill pipe side is always used for calculation due to its homogeneity rather calculation due to its homogeneity rather

than the contaminated casing sidethan the contaminated casing side

55..Balancing while circulationBalancing while circulation

• System PL = 2500psiSystem PL = 2500psi• Annulus PL = 100psi.Annulus PL = 100psi.• MW = 10.0ppgMW = 10.0ppg• Influx length=3000’Influx length=3000’• Hole depth = 10000’.Hole depth = 10000’.• Fm pressure=6000psi.Fm pressure=6000psi.• What should be the What should be the

imposed pressure on imposed pressure on both sides while both sides while circulation?circulation?

AnswerAnswer

A. FP=BHPan=BHPdpA. FP=BHPan=BHPdp

BHPan=HP+APL+IPBHPan=HP+APL+IP

6000=3640+100+IP6000=3640+100+IP

IPan=2260psiIPan=2260psi

B. BHPdp=HP+IPB. BHPdp=HP+IP

6000=5200+IP6000=5200+IP

IP=800psiIP=800psi

Cir.P.=2500+800=Cir.P.=2500+800=33003300psipsi

The pump rate at which the system The pump rate at which the system pressure loss is recorded for purpose pressure loss is recorded for purpose

of well control is called:-of well control is called:-Reduced circulating pressure,Reduced circulating pressure,Kill rate,Kill rate,Reduced pump rate,Reduced pump rate,Slow pump pressure,Slow pump pressure,Slow pump rate.Slow pump rate.

Shut-in PressureShut-in Pressure

The shut-in drill pipe The shut-in drill pipe pressure is the amount by pressure is the amount by

which the formation which the formation pressures exceeds the pressures exceeds the

hydrostatic head of the mud hydrostatic head of the mud in drill pipein drill pipe

Influx GradientInflux Gradient

Influx grad. = mud grad – (sicp-sidpp)Influx grad. = mud grad – (sicp-sidpp)

length of length of influxinflux

- Gas 1-3 ppgGas 1-3 ppg- Mix gas & water 3 -5 ppgMix gas & water 3 -5 ppg- Oil, water or mix. 5 -7 ppgOil, water or mix. 5 -7 ppg

Kill Weight MudKill Weight Mud

KWM = SIDPP + OMWKWM = SIDPP + OMW

0.052xTVD0.052xTVDOMW: Original mud weight.OMW: Original mud weight.

C. Killing ProceduresC. Killing Procedures

1.1. Wait and Weight Method.Wait and Weight Method.

2.2. Driller’s Method.Driller’s Method.

3.3. Concurrent Method.Concurrent Method.

1.Wait and Weight Method.1.Wait and Weight Method.

The well is shut-in, the surface mud is The well is shut-in, the surface mud is weighted and the kill weight mud is weighted and the kill weight mud is

pumped in one cyclepumped in one cycle..• Initial circulating pressure=SIDPP+SPRInitial circulating pressure=SIDPP+SPR• Final circ. Pressure= SPRx (KWM/OMW)Final circ. Pressure= SPRx (KWM/OMW)

1.The influx is pumped out first,1.The influx is pumped out first,

2.The well is shut-in until the mud is 2.The well is shut-in until the mud is weighted,weighted,

3.The kill weight mud is then pumped.3.The kill weight mud is then pumped.

2. The Driller Method.2. The Driller Method.

33 . .The Concurrent MethodThe Concurrent Method..

1.1. Pumping is begun immediately and the Pumping is begun immediately and the mud weight is raised while circulating the mud weight is raised while circulating the kick out.kick out.

2.2. It needs several cycles of circulation.It needs several cycles of circulation.

Kill SheetKill Sheet

The kill sheet includes The kill sheet includes all the necessary data all the necessary data for killing the well for killing the well including the drop including the drop down pressure down pressure against pumped against pumped strokes.strokes.

Kick ToleranceKick Tolerance

((Is the maximum allowable ((Is the maximum allowable pressure or its equivalent ppg that pressure or its equivalent ppg that

the weakest point in a wellbore the weakest point in a wellbore can withstand))can withstand))

• The weakest point is the casing shoe.The weakest point is the casing shoe.• No influx in the wellbore.No influx in the wellbore.• Kick toleance= [Shoe depth * (FR – MW)]/Depth.Kick toleance= [Shoe depth * (FR – MW)]/Depth.

II. Stuck pipeII. Stuck pipe

Drilling string Drilling string cannot be raised, cannot be raised, lowered or rotate.lowered or rotate.

Mechanisms of stuck pipeMechanisms of stuck pipe

A.A. Differential Stuck.Differential Stuck.

B.B. Wellbore Geometry.Wellbore Geometry.

C.C. Hole packing off.Hole packing off.

A. Differential StuckA. Differential Stuck

Sticking of pipe against a permeable Sticking of pipe against a permeable formation as the result of the pressure of formation as the result of the pressure of the mud in the hole exceeding the bore the mud in the hole exceeding the bore

fluid pressure.fluid pressure.

Differential stickingDifferential sticking

Stuck breadth = 4”Stuck breadth = 4” Stuck length = 25’Stuck length = 25’ Fm pressure = 4000 psiFm pressure = 4000 psi H pressure = 5000 psiH pressure = 5000 psi D. F=4*25*12*(5000-4000)D. F=4*25*12*(5000-4000)

1,200,0001,200,000lbslbs

Differential stickingDifferential sticking• Cause:Cause:

• Drill string contacts a permeable zone.Drill string contacts a permeable zone.• Developing of static filter cake.Developing of static filter cake.• High differential force.High differential force.

• Warning:Warning:• Prognosed low pressure sandsPrognosed low pressure sands• Long / unstabilized BHA.Long / unstabilized BHA.• Increasing overpull, slack off weight or torque Increasing overpull, slack off weight or torque

to start string movement.to start string movement.• First action:First action:

• Apply torque and jar down with maximum trip Apply torque and jar down with maximum trip load.load.

• Spot a pipe releasing pill if the string does not Spot a pipe releasing pill if the string does not jar free.jar free.

Preventing ActionPreventing Action

1.1. Maintain minimum required mud weight.Maintain minimum required mud weight.

2.2. Keep string moving when BHA is Keep string moving when BHA is opposite suspected zones.opposite suspected zones.

3.3. Minimize seepage loss in low pressure Minimize seepage loss in low pressure zones.zones.

4.4. Minimize unstabilized BHA & use spiral Minimize unstabilized BHA & use spiral DC.DC.

5.5. Control drill suspected zonesControl drill suspected zones

Hole diameter and / or angle relative to BHA Hole diameter and / or angle relative to BHA geometry and / or stiffness will not allow geometry and / or stiffness will not allow

passage of the drill stringpassage of the drill string

1.1. Key seatKey seat

2.2. MicrodoglegsMicrodoglegs

3.3. LedgesLedges

4.4. Stiff assemblyStiff assembly

5.5. Mobile formationMobile formation

6.6. Under gauge holeUnder gauge hole

B. Wellbore GeometryB. Wellbore Geometry

Key SeatKey Seat

Causes:Causes:1.1. Abrupt change in Abrupt change in

angle or direction in angle or direction in soft formations.soft formations.

2.2. High string tension High string tension and pipe rotation and pipe rotation wears a slot into the wears a slot into the formation.formation.

3.3. While POOH the drill While POOH the drill collars jam into the collars jam into the slot.slot.

Warning, indications, first actionWarning, indications, first action

Warning:Warning:

1.1. High angle doge leg in upper hole section.High angle doge leg in upper hole section.

2.2. Long drilling hours with no wiper trips through the Long drilling hours with no wiper trips through the dogleged sectiondogleged section

3.3. Cyclic over pull at tool joint intervals on trips.Cyclic over pull at tool joint intervals on trips.

Indications:Indications:

1.1. Occurs only while POOH.Occurs only while POOH.

2.2. Sudden over pull as BHA reaches dogleg depth.Sudden over pull as BHA reaches dogleg depth.

3.3. Unrestricted circulation.Unrestricted circulation.

4.4. Free string movement below key seat depth.Free string movement below key seat depth.

First Action, Preventive ActionFirst Action, Preventive Action

First action:First action: Applay torque and jar down.Applay torque and jar down. Attempt to rotate with low over pull to work Attempt to rotate with low over pull to work

through dogleg.through dogleg.

Preventive Action:Preventive Action: Minimize dog leg severity to 3deg/100’ or less.Minimize dog leg severity to 3deg/100’ or less. Limit over pull through suspected intervals.Limit over pull through suspected intervals. Run string reamer or key seat wiper if Run string reamer or key seat wiper if

suspected.suspected.

Formation cuttings cavings or medium to large Formation cuttings cavings or medium to large pieces of hard formation, cement or junk settle pieces of hard formation, cement or junk settle around the drill string and pack off/bridging the around the drill string and pack off/bridging the

annulus.annulus.

1.1. Settled cuttingsSettled cuttings

2.2. Shale instability +Shale instability +

3.3. Unconsolidated formationsUnconsolidated formations

4.4. Fractured formationsFractured formations

5.5. Cement related.Cement related.

6.6. Junk.Junk.

C. Packing Off & BridgingC. Packing Off & Bridging

Settled Cutting Straight HoleSettled Cutting Straight Hole

Causes:Causes:• Low annular velocity Low annular velocity

and/or poor mud and/or poor mud properties.properties.

• When circulation is When circulation is stopped, the stopped, the cuttings fall back cuttings fall back down the hole and down the hole and pack off the drill pack off the drill string.string.

Warning, Warning, indicationsindications, first action, first action

Warning:Warning:

1.1. High ROP, low pump rate, little to no circulation High ROP, low pump rate, little to no circulation time at connections.time at connections.

2.2. Torque, drag and pump pressure increase.Torque, drag and pump pressure increase.

3.3. Over pull off slips, pump surge to break Over pull off slips, pump surge to break circulationcirculation

4.4. Fill on bottom.Fill on bottom.

Indications:Indications:

1.1. Likely to occure on connections.Likely to occure on connections.

2.2. Possible during trips.Possible during trips.

3.3. Circulation restricted or impossible.Circulation restricted or impossible.

First Action, Preventive ActionFirst Action, Preventive Action

First action:First action: Applay low pump pressure (200-400psi).Applay low pump pressure (200-400psi). Apply torque and jar down.Apply torque and jar down. Circulate clean to avoid recurrence.Circulate clean to avoid recurrence.

Preventive Action:Preventive Action: Control ROP, maximize annular velocity.Control ROP, maximize annular velocity. Maintain sufficient gel strength and YP.Maintain sufficient gel strength and YP. Circulate 5- 10 min before connections.Circulate 5- 10 min before connections. Circulation clean before POOH.Circulation clean before POOH.

Settled Cutting Deviated HoleSettled Cutting Deviated Hole

Causes:Causes:• Drill cuttings settle on Drill cuttings settle on

the low side forming a the low side forming a cutting bed.cutting bed.

• The cutting bed The cutting bed builds and slide down builds and slide down hole.hole.

• While POOH the While POOH the cuttings is dragged cuttings is dragged upward by the BHAupward by the BHA

Warning, indications, first actionWarning, indications, first action

Warning:Warning:1.1. Hole angle > 35deg..Hole angle > 35deg..

2.2. Drilling with a down hole motor.Drilling with a down hole motor.

3.3. High ROP, low GPM, increase torque, increase High ROP, low GPM, increase torque, increase pump pressure.pump pressure.

Indications:Indications:1.1. Likely to occure while POOH, possible while Likely to occure while POOH, possible while

drilling.drilling.

2.2. Increase overpull on trips.Increase overpull on trips.

3.3. Circulating pressure restricted or impossibleCirculating pressure restricted or impossible

First Action, Preventive ActionFirst Action, Preventive Action

First action:First action: Apply low pump pressure (100-400psi).Apply low pump pressure (100-400psi). Jar down & Apply torque with caution .Jar down & Apply torque with caution . Circulate clean to avoid recurrence.Circulate clean to avoid recurrence.

Preventive Action:Preventive Action: Record trend indicators for inadequate hole Record trend indicators for inadequate hole

cleaning.cleaning. Control ROP, maintain mud properties, maximize Control ROP, maintain mud properties, maximize

annular velocity, maximize string rotation.annular velocity, maximize string rotation. Circulation clean before POOH.Circulation clean before POOH. Use low vis/high vis density sweps.Use low vis/high vis density sweps.