issues impacting the productivity of tight gas producing formations_bennion2004

8/8/2019 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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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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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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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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Capillary Equilibrium in GasCapillary Equilibrium in Gas

Reservoirs Reservoirs LOWLOW PermPerm


Capillar y

Pressu

re-P

si

RelativePerm

eability

FWC

Krw

Krg


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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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Non - Capillary Equilibrium in GasNon - Capillary Equilibrium in Gas

Reservoirs Reservoirs LOWLOW PermPerm


Capillar y

Pressu

re-P

si

RelativePerm

eability

NOFWC

Krw

Krg


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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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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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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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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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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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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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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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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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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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June 9, 2004June 9, 2004

Highway AnalogyHighway Analogy


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June 9, 2004June 9, 2004



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June 9, 2004June 9, 2004



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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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June 9, 2004June 9, 2004


Water Saturation

Water Saturation

Capillar y

Pressure

Relative

Perm


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June 9, 2004June 9, 2004


Water Saturation

Water Saturation

Capillar y

Pressure

Relative

Perm


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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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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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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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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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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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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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June 9, 2004June 9, 2004

DJ Basin J SandDJ Basin J Sand

Two Production Cycles

Slide Courtesy of Calfrac


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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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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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June 9, 2004June 9, 2004

Lab Regain Perm Test EquipmentLab Regain Perm Test Equipment


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ConclusionsConclusions


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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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June 9, 2004June 9, 2004

Thank You for YourThank You for Your

AttentionAttention


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J 9 2004J 9 2004

issues impacting the productivity of tight gas producing formations_bennion2004

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