under-balanced drilling fluids
TRANSCRIPT
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Candidate Candidate SelectionSelection
Harold Vance Department of Petroleum Engineering
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Under-Balanced Under-Balanced FluidsFluids
•Air (NAir (N22, , Gas)Gas)•MistMist•GaseatedGaseated•FoamFoam•Oil Oil •WaterWater•MudMud
Harold Vance Department of Petroleum Engineering
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Subjects Covered
• Candidate SelectionCandidate Selection• Flow DrillingFlow Drilling• AeratedAerated• FoamFoam• Air/Gas/NAir/Gas/N22
• CompletionsCompletions
Harold Vance Department of Petroleum Engineering
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Reasons for UB DrillingReasons for UB Drilling
1.1. Limit lost circulation Limit lost circulation 2.2. Improve drilling rate Improve drilling rate 3.3. Avoid differential Avoid differential
stickingsticking 4.4. Protect reservoir Protect reservoir
Other benefits are not Other benefits are not reasons.reasons.
Harold Vance Department of Petroleum Engineering
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ResultsResults
Improve the rate of Improve the rate of return on investment.return on investment.
(Broadened Scope)(Broadened Scope)
Harold Vance Department of Petroleum Engineering
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Historical PerspectiveHistorical Perspective
Candidate SelectionCandidate Selection
Harold Vance Department of Petroleum Engineering
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Cable ToolsCable Tools
• The first The first underbalanced drillers.underbalanced drillers.
• No skin damage. No skin damage. • Great production. Great production.
Harold Vance Department of Petroleum Engineering
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UB HistoryUB History
• 1938 - California Gas Drilling.1938 - California Gas Drilling.• 1948 - Aerated, Big Lake Texas.1948 - Aerated, Big Lake Texas.• 1960 - AEC Foam, Nuclear Holes.1960 - AEC Foam, Nuclear Holes.• 1965 - Aerated U.S.1965 - Aerated U.S.• 1968 - Chevron Foam, California.1968 - Chevron Foam, California.• 1986 - Aerated Canada.1986 - Aerated Canada.• 192? - Russia, Where? What?192? - Russia, Where? What?
Harold Vance Department of Petroleum Engineering
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Underbalanced Drilling AreasUnderbalanced Drilling Areas20002000
Lost Circulation. Drilling RateReservoir ProtectionGeothermal
Harold Vance Department of Petroleum Engineering
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Number of Underbalanced WellsNumber of Underbalanced Wellsin Canadain Canada
30120
230330
525
1500
00
200200
400400
600600
800800
10001000
12001200
14001400
16001600
Tota
l N
um
ber
of
Wells
Tota
l N
um
ber
of
Wells
19921992 19931993 19941994 19951995 19961996 19971997
YearYearHarold Vance Department of Petroleum Engineering
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New SubjectNew SubjectUnderbalance Fluids Underbalance Fluids
SummarySummary
Harold Vance Department of Petroleum Engineering
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Drilling Fluid DensitiesDrilling Fluid Densities
Air
Beg
in W
eigh
ted
Mud
Nat
ive
Cla
y &
Wat
ers
SaturatedSalt W
ater
Gel and W
ater
Stable Foam
Mist
Weighted Mud (Barite)
unds per Gallon
Poun
ds P
er
10.478
10.8
75 11.183
152
.02
.3
Types of Drilling Fluids and Their Relative DensitiesTypes of Drilling Fluids and Their Relative Densities
1.0
2.0
2.3
0.5
.4
0.002
0
1.2
Harold Vance Department of Petroleum Engineering
Types of Drilling Fluids and Their Relative Types of Drilling Fluids and Their Relative DensitiesDensities
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Categories of UB DrillingCategories of UB Drilling
• Air and gas drilling.Air and gas drilling.Mist drilling.Mist drilling.
• Foam drilling.Foam drilling.• Gaseated drilling.Gaseated drilling.• Flow drilling.Flow drilling.
Harold Vance Department of Petroleum Engineering
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Gas DrillingGas Drilling
• First commercial UB drilling First commercial UB drilling was with gas in the U.S. was with gas in the U.S. (1940’s)(1940’s)
Harold Vance Department of Petroleum Engineering
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Gas DrillingGas DrillingCommon Drilling GasesCommon Drilling Gases
• Air.Air.• Natural gas.Natural gas.• Nitrogen.Nitrogen.• Engine exhaust (Nitrogen).Engine exhaust (Nitrogen).
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Gas Drilling,Gas Drilling, Producing 3MM SCF/day Producing 3MM SCF/day
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First Widespread use came with First Widespread use came with development of portable air development of portable air
compressors.compressors.
Western Air Drilling, 1954Western Air Drilling, 1954
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Advantages of Gas Advantages of Gas DrillingDrilling
• Increase drilling rate.Increase drilling rate.• No lost circulation*No lost circulation*• No differential sticking.No differential sticking.• Minimal reservoir damage.Minimal reservoir damage.
Harold Vance Department of Petroleum Engineering
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Problems with Gas Problems with Gas DrillingDrilling
• Water.Water.• Washouts, especially in Washouts, especially in
coal.coal.• Corrosion.Corrosion.• Downhole fires with air.Downhole fires with air.• Crooked hole.Crooked hole.
Harold Vance Department of Petroleum Engineering
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Air/Mist DrillingAir/Mist Drilling
• Water & detergent is added Water & detergent is added to air (or gas) when the hole to air (or gas) when the hole becomes damp or when it is becomes damp or when it is too washed out to lift the too washed out to lift the cuttings.cuttings.
• Water added is normally Water added is normally between 5 bbl/hr to 10 bbl/hr between 5 bbl/hr to 10 bbl/hr (0.8 m (0.8 m33/hr to 1.5 m/hr to 1.5 m33/hr). /hr).
Harold Vance Department of Petroleum Engineering
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Categories of UB DrillingCategories of UB Drilling
• Air and gas drilling.Air and gas drilling.• Foam drilling.Foam drilling.• Gaseated drilling.Gaseated drilling.• Flow drilling.Flow drilling.
Harold Vance Department of Petroleum Engineering
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Foam DrillingFoam Drilling
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FOAMFOAMHas the greatest Has the greatest
potentialpotential of of
any of the “Light” any of the “Light” fluids.fluids.
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Advantages of Foam Advantages of Foam DrillingDrilling
• Great lifting capacity.Great lifting capacity.• Controllable BHP.Controllable BHP.• Increase drilling rate.Increase drilling rate.• No lost circulation*No lost circulation*• No differential sticking.No differential sticking.• Minimal reservoir Minimal reservoir
damage.damage.Harold Vance Department of Petroleum Engineering
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Problems with Foam Problems with Foam DrillingDrilling
• Complex mixture-Hard to get a Complex mixture-Hard to get a proper mixture and maintain it proper mixture and maintain it properly.properly.
• Disposal/Storage.Disposal/Storage.• Cost.Cost.
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Categories of UB DrillingCategories of UB Drilling
• Air and gas Air and gas drilling.drilling.
• Foam drilling.Foam drilling.• Gaseated drilling.Gaseated drilling.• Flow drilling.Flow drilling.
Harold Vance Department of Petroleum Engineering
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Gaseated DrillingGaseated Drilling
• Gaseated or aerated drilling Gaseated or aerated drilling uses a mixture of fluid and uses a mixture of fluid and gas.gas.
• Gas may generally be any gas.Gas may generally be any gas.• Fluid may be from oil to water Fluid may be from oil to water
to drilling mud.to drilling mud.• No binding agent is used No binding agent is used
(foamer).(foamer).
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Gaseated SeparatorGaseated Separator
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Advantages Advantages of Gaseated Drillingof Gaseated Drilling
• Increase drilling rate.Increase drilling rate.• No lost circulation*No lost circulation*• No differential sticking.No differential sticking.• Minimal reservoir Minimal reservoir
damage.damage.
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Problems Problems with Gaseated Drillingwith Gaseated Drilling
• Surging (causing Surging (causing overpressures or overpressures or caving).caving).
• Corrosion (not with Corrosion (not with nitrogen).nitrogen).
• Hole caving.Hole caving.
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Categories of UB DrillingCategories of UB Drilling
• Air and gas drilling.Air and gas drilling.• Foam drilling.Foam drilling.• Gaseated drilling.Gaseated drilling.• Flow drilling.Flow drilling.
Harold Vance Department of Petroleum Engineering
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Flow DrillingFlow Drilling
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Flow DrillingFlow Drilling
Conventional Mud Used in an Conventional Mud Used in an Underbalanced ConditionUnderbalanced Condition
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Advantages of Flow Advantages of Flow DrillingDrilling
• Uses regular mud Uses regular mud system.system.
• Least expensive way of Least expensive way of UB drilling.UB drilling.
• No lost returns.No lost returns.• No differential sticking.No differential sticking.• Improved ROP.Improved ROP.
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Problems with Flow Problems with Flow DrillingDrilling
• Limited ability to reduce Limited ability to reduce annular pressure below annular pressure below “normal” reservoir pressures.“normal” reservoir pressures.
• Drilling with a constant well Drilling with a constant well flow or potential of well flow.flow or potential of well flow.
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• All have problems.All have problems.• Nothing works all the Nothing works all the
time.time.• UB does not improve UB does not improve
production all of the time.production all of the time.
All Good IdeasAll Good Ideas
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COMMENTS!!COMMENTS!!
Underbalanced Drilling Underbalanced Drilling BenefitsBenefits
Candidate SelectionCandidate Selection
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• New processes involve New processes involve risk.risk.
• Budget enough money.Budget enough money.• Don’t promise too much.Don’t promise too much.
Underbalanced DrillingUnderbalanced Drilling
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Have at Least One Have at Least One Good Good Economic Economic
ReasonReason or or
Technical ReasonTechnical Reason
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Remember the Learning Remember the Learning Curve !!!!Curve !!!!
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UB Drilling UB Drilling ApplicationsApplications
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UB Drilling ApplicationsUB Drilling Applications
• Drilling.Drilling.• Lost returns.Lost returns.• Drilling rate.Drilling rate.• Differential pressure Differential pressure
sticking.sticking.• Limited water.Limited water.• Reservoir protection.Reservoir protection.
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Lost ReturnsLost Returns
• Reduce the mud density.Reduce the mud density.• Don’t add junk.Don’t add junk.
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Lost Circulation Lost Circulation CandidatesCandidates
• Permeability > 1,000 md.Permeability > 1,000 md.• Large fractures (>100 micron Large fractures (>100 micron
opening).opening).• Vugular porosity.Vugular porosity.• Overbalanced > 1,000 psi with Overbalanced > 1,000 psi with
conventional fluids.conventional fluids.
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70
60
50
40
30
20
10
00 1000 2000 3000 4000
AUSTIN CHALKAUSTIN CHALK
MANCOS SHALEMANCOS SHALE
COLTON SANDSTONECOLTON SANDSTONE
DR
ILLIN
G R
ATE (
ft/ h
r)
7-7/8 TRICONE BIT7-7/8 TRICONE BIT30,000 lbs. WOB30,000 lbs. WOB60 RPM60 RPM
pp
bp
DIFFERENTIAL PRESSURE (psi)
Increased Drilling RateIncreased Drilling RateEffect of Differential Effect of Differential
PressurePressure
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-500 0 +500 +1000
Drilling Rate-UBDrilling Rate-UBEffect of Differential Effect of Differential
PressurePressure
Bit Bit FlounderFlounder
Perfect Perfect CleaningCleaning
Harold Vance Department of Petroleum Engineering
DR
ILLIN
G R
ATE (
ft/ h
r)
DIFFERENTIAL PRESSURE (psi)
p
pb
p
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Hard Rock & Crooked Hard Rock & Crooked HoleHole
• Air Hammer.Air Hammer.• Pendulum.Pendulum.
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Differential Pressure Differential Pressure StickingSticking
DRILL PIPEDRILL PIPE
FILTER CAKEFILTER CAKE
DRILL COLLARDRILL COLLAR
, K, K
PPff
PHPH
PH > PPH > Pff
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Limited WaterLimited Water
Desert & Semi-Arid RegionsDesert & Semi-Arid RegionsAlgeriaAlgeriaSouth YemenSouth YemenLibyaLibyaSW United StatesSW United States
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UB Drilling Applications UB Drilling Applications (2)(2)
• Formation damage avoidance.Formation damage avoidance.Skin damage.Skin damage.Fluid-fluid sensitivity.Fluid-fluid sensitivity.Fluid-formation sensitivity.Fluid-formation sensitivity.Depleted zones.Depleted zones.
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Formation DamageFormation Damage
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• Slow drilling rate.Slow drilling rate.• Lost returns.Lost returns.• Differential pressure Differential pressure
sticking.sticking.• Reservoir damage.Reservoir damage.
Depleted ZonesDepleted Zones
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Skin DamageSkin Damage
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Reservoir Reservoir CoreCore
Filter CakeFilter Cake
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Skin Damage Due to Skin Damage Due to Filter Cake and Mud SolidsFilter Cake and Mud Solids
10 micron 10 micron pore throatpore throat1-3 micron 1-3 micron solidssolids
10 micron pore 10 micron pore throatthroat1 micron & 1 micron & smaller solidssmaller solids
10 micron pore 10 micron pore throatthroat10 micron 10 micron solids & somesolids & somesmaller solidssmaller solids
Effective Effective ExternalExternal
Filtrate SealFiltrate Seal
Internal Internal PlugginPluggin
gg
Ineffective Ineffective ExternalExternalSeal for Seal for
SmallSmallFines & Fines & FiltrateFiltrate
10u10u
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Skin DamageSkin DamageAvoidance TechniquesAvoidance Techniques
•UB DrillingUB Drilling•Non-Invasive Mud CakeNon-Invasive Mud Cake•Ultra Clean Drill-in FluidUltra Clean Drill-in Fluid
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Fluid Fluid
SensitivitySensitivity1.1. Fluid-Formation Reaction (Shale Instability) Fluid-Formation Reaction (Shale Instability)
Fluid-Fluid Reaction Fluid-Fluid Reaction (Emulsions)(Emulsions)
2.2.
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Mechanism for Formation Mechanism for Formation BlockingBlocking(Bennion, 1995)(Bennion, 1995)
Non Non WettingWettingPhasePhase
Non Non WettinWettin
gg
Non Non WettingWettingPhasePhase
FinesFinesWettingWettingPhasePhase
Case 1 Non-Wetting
phase in motion-
minimal fines migration
Case 2 Case 2 Wetting phaseWetting phase
in motion -in motion -potential for fines potential for fines
migrationmigration
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FormationFormation Damage - Fractured Formations Damage - Fractured Formations
Fracture PluggingFracture Plugging
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UB Drilling in Fractured UB Drilling in Fractured ReservoirsReservoirs
GravityGravityDisplacementDisplacement
Fluid Fluid BalanceBalanceor Micro or Micro FractureFracture
21 Drilling FluidDrilling FluidProduced FluidProduced Fluid
No Invasion of“Top” FracturesWhile Underbalanced
Harold Vance Department of Petroleum Engineering
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Potential Formation DamagePotential Formation Damage Mechanism in Different Sand Reservoir Mechanism in Different Sand Reservoir
TypesTypes
DamageMechanism F
luid
-Flu
idIn
com
pati
bilit
y
Rock-F
luid
Incom
pati
bilit
y
Solid
sIn
vasio
n
Ph
ase
Tra
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Ch
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ical
Ad
sorp
tion
Fin
es
Mig
rati
on
Bio
log
ical
Dam
ag
e
Eff
ect
of
Hig
hO
verb
ala
nced
HomogenousSand-Clean
HomogenousSand-Dirty
LaminatedSand-Clean
LaminatedSand-Dirty
UnconsolidatedSand
Fractured SandPerm-Matrix
Probable Possible Probable Possible Unlikely Unlikely Harold Vance Department of Petroleum Engineering
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DamageMechanism F
luid
-Flu
idIn
com
pati
bilit
y
Rock-F
luid
Incom
pati
bilit
y
Solid
sIn
vasio
n
Ph
ase
Tra
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ing
Ch
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ical
Ad
sorp
tion
Fin
es
Mig
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on
Bio
log
ical
Dam
ag
e
Eff
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of
Hig
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verb
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nced
HomogenousCarbonate
Fractured CarbonateImpermeable Matrix
VugularCarbonate
Fractured CarbonatePermeable Matrix
Harold Vance Department of Petroleum Engineering
Potential Formation DamagePotential Formation Damage Mechanism in Different Sand Reservoir Mechanism in Different Sand Reservoir
TypesTypes
Probable Possible Probable Possible Unlikely Unlikely
Fractured SandLow Perm Matrix
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Underbalanced Drilling Underbalanced Drilling LimitationsLimitations
Candidate SelectionCandidate Selection
Harold Vance Department of Petroleum Engineering
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UB LimitsUB Limits
• UB is not an UB is not an enhancement technique.enhancement technique.
• Mud column pressure is Mud column pressure is not a seal against:not a seal against: Well kick.Well kick. Broken or fractured formation.Broken or fractured formation. Weak formations.Weak formations. Heaving shale.Heaving shale.
Harold Vance Department of Petroleum Engineering
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Underbalanced Underbalanced ProblemProblem
ROTATING BOPs
SOLID/LIQUID/GASSEPARATION
COMPRESSOR / N2
COST
CORROSION
VIBRATIONS
HYDRAULIC CALCULATIONS
CUTTINGS LIFTING
FLUID INFLUX
BOREHOLESTABILITY
MWD TRANSMISSION
HIGH TORQUE/DRAG
UNDERBALANCEDCOMPLETION
FIRE/EXPLOSIONS
Harold Vance Department of Petroleum Engineering
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If a reservoir will If a reservoir will
not produce not produce
without fracturing without fracturing
it is probably a it is probably a
poor UB prospect.poor UB prospect.
Harold Vance Department of Petroleum Engineering
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WarningWarning
A poor prospect can prove failure. You must gamble with a well that can succeed.
Harold Vance Department of Petroleum Engineering
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The “Absolute” Rule for The “Absolute” Rule for UB OperationsUB Operations
……IT’S NOT WHAT YOU KNOW IT’S NOT WHAT YOU KNOW THAT HURTS YOU.THAT HURTS YOU.
……IT’S WHAT YOU KNOW THAT’S IT’S WHAT YOU KNOW THAT’S NOT TRUE!NOT TRUE!
Harold Vance Department of Petroleum Engineering
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The No-Go ScreenThe No-Go ScreenThe No-Go ScreenThe No-Go Screen
If the following occurs within the If the following occurs within the open hole section:open hole section:
DON’T DRILL UNDERBALANCEDDON’T DRILL UNDERBALANCED
1. Geopressured shales1. Geopressured shales2. Steeply dipping fractured 2. Steeply dipping fractured formationsformations3. Thick broken coals 3. Thick broken coals 4. What about sands? - not 4. What about sands? - not sandstonesandstone
Harold Vance Department of Petroleum Engineering
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Primary Cause of Well Primary Cause of Well Bore CollapseBore Collapse
Primary Cause of Well Primary Cause of Well Bore CollapseBore Collapse
• NATURAL CAUSESNATURAL CAUSESFractured or Faulted ZonesFractured or Faulted ZonesHigh Pore Pressure High Pore Pressure
(Geopressure)(Geopressure)Weak, Low Strength RocksWeak, Low Strength RocksHigh in Situ StressesHigh in Situ Stresses
Harold Vance Department of Petroleum Engineering
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Primary Causes of Well Primary Causes of Well Bore CollapseBore Collapse
INDUCED PROBLEMSINDUCED PROBLEMSPressure SurgesPressure SurgesWetted ShalesWetted Shales
Harold Vance Department of Petroleum Engineering
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WELLSTAB - MEI Wellbore Stability ModelMechanical/Chemical Stability Design
Multi-Depth AnalysisMicrosoft Office Report
Harold Vance Department of Petroleum Engineering
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ENDEND
Harold Vance Department of Petroleum Engineering