Issues Impacting the Productivity of Tight Gas Producing Formations_Bennion2004
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FORMATION DAMAGEFORMATION DAMAGE
ISSUES IMPACTING THEISSUES IMPACTING THE
PRODUCTIVITY OF TIGHTPRODUCTIVITY OF TIGHT
GAS PRODUCINGGAS PRODUCING
FORMATIONSFORMATIONSBrant BennionBrant Bennion
Hycal Energy Research Laboratories Ltd.Hycal Energy Research Laboratories Ltd.
Canadian Well Logging SocietyCanadian Well Logging Society
June 9, 2004June 9, 2004
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CWLS PresentationCWLS PresentationJune 9, 2004June 9, 2004
Presentation SummaryPresentation SummaryWhat is formation DamageWhat is formation Damage
Definition of a tight gas reservoirDefinition of a tight gas reservoir
Conditions generally required forConditions generally required foreconomic tight gas reservoir productioneconomic tight gas reservoir production
Common formation damage typesCommon formation damage types
occurring in tight gas reservoirsoccurring in tight gas reservoirsReducing formation damage in tight gasReducing formation damage in tight gas
reservoirsreservoirs
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CWLS PresentationCWLS PresentationJune 9, 2004June 9, 2004
What is Formation Damage?What is Formation Damage?
Any process causing a reductionAny process causing a reduction
in thein the inherentinherent naturalnatural
permeability of an oil or gaspermeability of an oil or gasproducing formationproducing formation
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CWLS PresentationCWLS PresentationJune 9, 2004June 9, 2004
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CWLS PresentationCWLS PresentationJune 9, 2004June 9, 2004
What is a Tight Gas Reservoir?What is a Tight Gas Reservoir?
Somewhat arbitrary classificationSomewhat arbitrary classification
Often defined as a gas bearing sandstoneOften defined as a gas bearing sandstone
or carbonate matrix (which may or mayor carbonate matrix (which may or may
not contain natural fractures) whichnot contain natural fractures) which
exhibits an in-situ permeability to gas ofexhibits an in-situ permeability to gas of
less than 0.10 mDless than 0.10 mD
Many ultra tight gas reservoirs may haveMany ultra tight gas reservoirs may have
in-situ permeability down to 0.001 mDin-situ permeability down to 0.001 mD
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CWLS PresentationCWLS PresentationJune 9, 2004June 9, 2004
What Controls the Ability toWhat Controls the Ability to
Economically Produce Tight GasEconomically Produce Tight Gas
Reserves?Reserves?Effective permeabilityEffective permeability
Initial saturation conditionsInitial saturation conditions
Size of effective sand face drainage areaSize of effective sand face drainage areaaccessed by the completionaccessed by the completion
Reservoir pressureReservoir pressure
Degree of liquid dropout from gas (rich vs.Degree of liquid dropout from gas (rich vs.
dry gas)dry gas)
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CWLS PresentationCWLS PresentationJune ,9 2 00 4June ,9 2 00 4
Capillary Equilibrium in GasCapillary Equilibrium in Gas
Reservoirs Reservoirs HighHigh PermPerm
Water Saturation Water Saturation
Capillar y
Pressu
re-P
si
RelativePerm
eability
FWC
Krw
Krg
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CWLS PresentationCWLS PresentationJune 9, 2004June 9, 2004
Capillary Equilibrium in GasCapillary Equilibrium in Gas
Reservoirs Reservoirs LOWLOW PermPerm
Water Saturation Water Saturation
Capillar y
Pressu
re-P
si
RelativePerm
eability
FWC
Krw
Krg
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CWLS PresentationCWLS PresentationJune 9, 2004June 9, 2004
Generally if a Tight Gas Matrix is inGenerally if a Tight Gas Matrix is in
Equilibrium With a Free WaterEquilibrium With a Free WaterContact, Unless Very Large VerticalContact, Unless Very Large Vertical
Relief is Present, Equilibrium WaterRelief is Present, Equilibrium Water
Saturation Reduces Reserves andSaturation Reduces Reserves and
Permeability to Gas Below thePermeability to Gas Below the
Economic Limit for ProductionEconomic Limit for Production
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CWLS PresentationCWLS PresentationJune 9, 2004June 9, 2004
Non - Capillary Equilibrium in GasNon - Capillary Equilibrium in Gas
Reservoirs Reservoirs LOWLOW PermPerm
Water Saturation Water Saturation
Capillar y
Pressu
re-P
si
RelativePerm
eability
NOFWC
Krw
Krg
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CWLS PresentationCWLS PresentationJune 9, 2004June 9, 2004
For Significant Reserves and MobileFor Significant Reserves and Mobile
Gas Production in Very Low Perm GasGas Production in Very Low Perm Gas
Reservoirs, aReservoirs, a CAPILLARYCAPILLARY
SUBNORMALSUBNORMAL Water SaturationWater Saturation
Condition Usually Must ExistCondition Usually Must Exist
Water Gauge
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CWLS PresentationCWLS PresentationJune 9, 2004June 9, 2004
Subnormally Water Saturated TightSubnormally Water Saturated Tight
Gas Reservoirs What Are TheyGas Reservoirs What Are They
A gas reservoir in which the initial waterA gas reservoir in which the initial water
saturation is less than that which would besaturation is less than that which would be
achieved on a conventional drainageachieved on a conventional drainagecapillary pressure curve at the effectivecapillary pressure curve at the effective
capillary gradient of the reservoircapillary gradient of the reservoir
P t l t d M h i F
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CWLS PresentationCWLS PresentationJune 9, 2004June 9, 2004
Postulated Mechanism ForPostulated Mechanism For
Establishment of the Low SwiEstablishment of the Low Swi
ConditionConditionLow Perm matriLow Perm matri
Initially 100%Initially 100%
Saturated withSaturated with
WaterWater
Gas Migration commencesGas Migration commences
Pore system displaced toPore system displaced to
Capillary equilibrium swirrCapillary equilibrium swirr
ore System is isolated fromore System is isolated from
ynamic capillary contactynamic capillary contact
ith active recharge waterith active recharge water
ource (faulting, etc)ource (faulting, etc)
ong Term Migration of Gasong Term Migration of Gas
lightly out of equilibrium withlightly out of equilibrium with
eservoir results in Desiccationeservoir results in Desiccationf water saturation to subnormalf water saturation to subnormal
aluealue
P t l t d M h i F
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CWLS PresentationCWLS PresentationJune 9, 2004June 9, 2004
Postulated Mechanism ForPostulated Mechanism For
Establishment of the Low SwiEstablishment of the Low Swi
ConditionConditionesults in unique combinatioesults in unique combinatio
f low perm and low Swif low perm and low Swi
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CWLS PresentationCWLS PresentationJune 9, 2004June 9, 2004
Subnormal SaturationSubnormal Saturation
ConditionsConditionsGenerally a pre-requisite for an economicGenerally a pre-requisite for an economic
gas reservoir in ultra tight rock (
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Common Subnormally SaturatedCommon Subnormally Saturated
Formations in Western CanadaFormations in Western Canada Deep basin areaDeep basin area
PaddyPaddy CadominCadomin CadotteCadotte
Jean MarieJean Marie
MontneyMontney Rock CreekRock Creek OstracodOstracod GethingGething BlueskyBluesky HalfwayHalfway DoigDoig CardiumCardium VikingViking
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Subnormal Initial Water SaturationSubnormal Initial Water Saturation
Gas ReservoirsGas ReservoirsUSAUSA
Powder River BasinPowder River BasinGreen River BasinGreen River Basin
DJ BasinDJ BasinPermian BasinPermian Basin
Also documented in South America,Also documented in South America,
Europe, Asia, Africa and AustraliaEurope, Asia, Africa and Australia
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Dominant Formation DamageDominant Formation Damage
Mechanisms in Tight GasMechanisms in Tight GasUnless natural microfractures are present,Unless natural microfractures are present,
almost all tight reservoirs must be fracturealmost all tight reservoirs must be fracturestimulated to obtain economic productionstimulated to obtain economic production
ratesrates In the case where fracture stimulation isIn the case where fracture stimulation is
required, classic formation damagerequired, classic formation damageassociated with drilling is not normallyassociated with drilling is not normallyproblematic due to the radius ofproblematic due to the radius ofpenetration of the fracture treatmentpenetration of the fracture treatment
E ti Ti ht M t i WithE ti Ti ht M t i With
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Exceptions Tight Matrix WithExceptions Tight Matrix With
Enhanced Natural PermeabilityEnhanced Natural Permeability
ConduitsConduitsNatural fracturesNatural fractures InterconnectedInterconnected
vugular porosityvugular porosity
Possible deepPossible deep
invasion of wholeinvasion of whole
drilling fluidsdrilling fluids
Possible applicationPossible applicationof UBDof UBD
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Hydraulically Fractured Tight GasHydraulically Fractured Tight Gas
SystemsSystems High fracture conductivity essential (proppantHigh fracture conductivity essential (proppant
crushing, embedment, residual gel/frac fluidcrushing, embedment, residual gel/frac fluid
entrainment are issues)entrainment are issues)
Water or hydrocarbon based phase trapping aWater or hydrocarbon based phase trapping amajor source of matrix damage in the near fracmajor source of matrix damage in the near frac
face areaface area
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Highway AnalogyHighway Analogy
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Highway AnalogyHighway Analogy
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Highway AnalogyHighway Analogy
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Water Based Phase TrappingWater Based Phase Trapping
Water Saturation
Water Saturation
Capillar y
Pressure
Relative
Perm
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Water Based Phase TrappingWater Based Phase Trapping
Water Saturation
Water Saturation
Capillar y
Pressure
Relative
Perm
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Water Based Phase TrappingWater Based Phase Trapping
Water Saturation
Water Saturation
Capillar y
Pressure
Relative
Perm
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Reducing Water Based Phase TrapReducing Water Based Phase Trap
PotentialPotentialAvoid use of water based fluids (OB, pureAvoid use of water based fluids (OB, pure
gas, etc)gas, etc)Use surface tension reducing agents toUse surface tension reducing agents to
reduce capillary pressure and trappingreduce capillary pressure and trappingpotential (mutual solvents, alcohols, etc)potential (mutual solvents, alcohols, etc)
Low fluid loss systems with rapid recoveryLow fluid loss systems with rapid recovery
times to minimize imbibitiontimes to minimize imbibitionMay also be an issue in someMay also be an issue in some
underbalanced operationsunderbalanced operations
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Using Hydrocarbon Based Fluids inUsing Hydrocarbon Based Fluids in
Reservoir Prone to Water TrappingReservoir Prone to Water Trapping
May still be the preferred method asMay still be the preferred method as
relative volume ofrelative volume ofnon wettingnon wetting phasephasehydrocarbon which is trapped is oftenhydrocarbon which is trapped is often
much less than watermuch less than water
Resulting damage is far less than if waterResulting damage is far less than if water
based fluid had been used in the samebased fluid had been used in the same
situation in many casessituation in many cases
Hydrocarbon vs Water BasedHydrocarbon vs Water Based
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Hydrocarbon vs. Water BasedHydrocarbon vs. Water Based
Fluids in Low Perm, Low Swi GasFluids in Low Perm, Low Swi Gas
ReservoirsReservoirs
Total fluid saturationTotal fluid saturation
R
ela
tive
R
ela
tive
p
ermea
bilit
y
p
ermea
bilit
y
Hydrocarbon vs Water BasedHydrocarbon vs Water Based
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Hydrocarbon vs. Water BasedHydrocarbon vs. Water Based
Fluids in Low Perm, Low Swi GasFluids in Low Perm, Low Swi Gas
ReservoirsReservoirs
R
ela
tive
R
ela
tive
p
ermea
bilit
y
p
ermea
bilit
y
Total fluid saturationTotal fluid saturation
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Common Stimulation TreatmentsCommon Stimulation Treatments
for Water Blocksfor Water Blocks
Dry gas injection (natural gas, CO2)Dry gas injection (natural gas, CO2)
Mutual Solvent Injection (methanol, CO2)Mutual Solvent Injection (methanol, CO2)
Extended shut in timeExtended shut in timeFormation heat treatmentFormation heat treatment
Direct penetration (fracturing/refracturing)Direct penetration (fracturing/refracturing)
High drawdowns normally not effectiveHigh drawdowns normally not effective
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
DJ Basin ColoradoDJ Basin Colorado
Reservoir ParametersReservoir Parameters Very fine grained sandstoneVery fine grained sandstone Depth 2400 mDepth 2400 m BHP = 20 MPaBHP = 20 MPa
kh = 1 4 mD-ft (0.3 1.2 mD-m)kh = 1 4 mD-ft (0.3 1.2 mD-m) Typical treatmentTypical treatment
550,000 lbs (250 tonnes) in X-linked water550,000 lbs (250 tonnes) in X-linked water
Post-frac productionPost-frac production 50 mcf/day 500 mcf/day50 mcf/day 500 mcf/day
Slide Courtesy of Calfrac
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
DJ Basin J SandDJ Basin J Sand
Two Production Cycles
Slide Courtesy of Calfrac
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Common Stimulation TreatmentsCommon Stimulation Treatments
for Hydrocarbon Blocksfor Hydrocarbon Blocks
High pressure lean gas injectionHigh pressure lean gas injection
(natural gas, nitrogen)(natural gas, nitrogen)
Lower pressure rich gas injectionLower pressure rich gas injection(CO2, ethane, propane, butane)(CO2, ethane, propane, butane)
Mutual solvent (heavy alcohol)Mutual solvent (heavy alcohol)
treatmentstreatments
Diagnosis of Problems and EvaluationDiagnosis of Problems and Evaluation
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Diagnosis of Problems and EvaluationDiagnosis of Problems and Evaluation
of Most Effective Prevention orof Most Effective Prevention or
Stimulation TreatmentsStimulation TreatmentsA variety of lab/core evaluation techniquesA variety of lab/core evaluation techniques
exist to evaluateexist to evaluateWater and hydrocarbon phase trap potentialWater and hydrocarbon phase trap potential
Interplay of reservoir pressure, invasion andInterplay of reservoir pressure, invasion and
drawdown effectsdrawdown effects
Evaluation of optimum stimulation methods forEvaluation of optimum stimulation methods for
existing damaged wellsexisting damaged wellsEvaluation of optimum drilling and completionEvaluation of optimum drilling and completion
methods in naturally fractured formationsmethods in naturally fractured formations
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Lab Regain Perm Test EquipmentLab Regain Perm Test Equipment
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ConclusionsConclusions
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
ConclusionsConclusions
Tight gas reservoirs have a huge future potentialTight gas reservoirs have a huge future potentialfor productionfor production
Generally to be economic tight gas reservoirsGenerally to be economic tight gas reservoirsare normally in a subnormal water saturationare normally in a subnormal water saturation
conditioncondition Fluid trapping tends to be a dominant damageFluid trapping tends to be a dominant damage
mechanism for tight gas reservoirsmechanism for tight gas reservoirs Techniques exist to evaluate and minimizeTechniques exist to evaluate and minimize
phase trapping problems and to stimulatephase trapping problems and to stimulateexisting damaged wellsexisting damaged wells
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CWLS PresentationCWLS Presentation
June 9, 2004June 9, 2004
Thank You for YourThank You for Your
AttentionAttention
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CWLS PresentationCWLS Presentation
J 9 2004J 9 2004