waterflooding seminar ()

Waterflooding Presentation – April 11, 2002Waterflooding Presentation – April 11, 2002

WATERFLOODINGWATERFLOODING

Hycal - WeatherfordHycal - WeatherfordApril 2005April 2005

Presentation SummaryPresentation Summary Why does (and doesn’t) waterflooding Why does (and doesn’t) waterflooding

work in various reservoir situationswork in various reservoir situations What are the optimum conditions for What are the optimum conditions for

waterfloodingwaterflooding What are some common problems What are some common problems

associated with waterfloodingassociated with waterflooding What are some novel applications for What are some novel applications for

waterflooding?waterflooding? Summary and conclusionsSummary and conclusions

Why Does the Basic Treatise of Why Does the Basic Treatise of Waterflooding ‘Work’ as a Cost Waterflooding ‘Work’ as a Cost

Effective Recovery Method?Effective Recovery Method?Compare to unsupported (non water Compare to unsupported (non water

injection/influx supported) primary oil injection/influx supported) primary oil production to understand thisproduction to understand this

Primary Oil Production MethodsPrimary Oil Production Methods

Oil Compression Drive (0.1-2% Oil Compression Drive (0.1-2% OOIP)OOIP)

Compaction Drive (0.1 – 2% Compaction Drive (0.1 – 2% OOIP)OOIP)

Solution gas drive (1-10% OOIP)Solution gas drive (1-10% OOIP)Gascap drive (1-20% OOIP)Gascap drive (1-20% OOIP)

Solution Gas and Gascap Drives Solution Gas and Gascap Drives Have Limited Recovery Generally Have Limited Recovery Generally

Due to Adverse Viscosity and Due to Adverse Viscosity and Mobility EffectsMobility Effects

Waterflooding is Often Much Waterflooding is Often Much More Effective Than Gasflooding More Effective Than Gasflooding

Due to Due to Much better viscosity ratio results in better Much better viscosity ratio results in better

conformance and reduced coningconformance and reduced coningLower density contrast minimizing gravity Lower density contrast minimizing gravity

segregation in horizontal drive situationssegregation in horizontal drive situationsMaintenance of driving pressure gradient Maintenance of driving pressure gradient

in reservoirin reservoirPrevention of formation of critical or free Prevention of formation of critical or free

gas saturations which reduce relative gas saturations which reduce relative permeability to oilpermeability to oil

Waterflood RecoveryWaterflood RecoveryDepends strongly on a number of factors Depends strongly on a number of factors

to be discussedto be discussedCan be as high as 60% of the OOIP in Can be as high as 60% of the OOIP in

place in some favorable situationsplace in some favorable situationsMay be much lower in other casesMay be much lower in other casesThere are generally optimum reservoir There are generally optimum reservoir

types, conditions and implementation types, conditions and implementation strategies for waterflooding to maximize strategies for waterflooding to maximize potential oil recoverypotential oil recovery

TYPES OF TYPES OF WATERFLOOD WATERFLOOD OPERATIONSOPERATIONS

Natural WaterfloodingNatural Waterflooding

Infinite Aquifer Type WaterfloodInfinite Aquifer Type Waterflood

1 m31 m3OutOut

1 m31 m3InIn

Limited Aquifer Type WaterfloodLimited Aquifer Type Waterflood

1 m31 m3OutOut

0.5 m30.5 m3InIn

Passive Aquifer Type WaterfloodPassive Aquifer Type Waterflood

1 m31 m3OutOut

0 m30 m3InIn

Modes of Natural WaterfloodsModes of Natural Waterfloods

Vertical drive (most effective)Vertical drive (most effective)Edge or horizontal drive (less Edge or horizontal drive (less

effective)effective)

Vertical Flood (Common in Reef Vertical Flood (Common in Reef Structures, thick vertical pay sections)Structures, thick vertical pay sections)

Edge Flood – Common in Thin Edge Flood – Common in Thin Pay Zones with Little Vertical Pay Zones with Little Vertical

ReliefRelief

‘‘Induced’ WaterfloodsInduced’ Waterfloods

Induced WaterfloodsInduced Waterfloods In cases where good voidage replacement In cases where good voidage replacement

by natural aquifer support is not present by natural aquifer support is not present waterflooding is often conducted by waterflooding is often conducted by injection of surface, produced or other injection of surface, produced or other water into the formation of interest to water into the formation of interest to simulate various types of natural water simulate various types of natural water drivedrive

Common Induced Waterflood Common Induced Waterflood TypesTypes

Edge drive (updip)Edge drive (updip)Bottom drive (gravity stabilized)Bottom drive (gravity stabilized)Line DriveLine DriveAdvancing line driveAdvancing line driveStaggered line driveStaggered line drivePatternPatternReservoir dictatedReservoir dictated

Updip Edge DriveUpdip Edge Drive

Vertically Stable Bottom DriveVertically Stable Bottom Drive

Line DriveLine Drive

Advancing Line DriveAdvancing Line Drive

Staggered Line DriveStaggered Line Drive

Pattern Flooding – 5 SpotPattern Flooding – 5 Spot

Reservoir Controlled OrientationReservoir Controlled Orientation

100 200 300 400 500 600 700 800

Factors Impacting Factors Impacting the Displacement the Displacement Effectiveness of a Effectiveness of a

WaterfloodWaterflood

MACROSCALE EFFECTSMACROSCALE EFFECTSHeterogeneityHeterogeneityPermeability contrastsPermeability contrastsReservoir continuityReservoir continuityFaults and fracturesFaults and fracturesDirectional permeability trendsDirectional permeability trends

MICROSCALE EFFECTSMICROSCALE EFFECTSPore size distribution and geometryPore size distribution and geometryCapillary pressureCapillary pressureWettabilityWettabilityRelative permeability characterRelative permeability characterAdvance rateAdvance rateInjection fluid induced damageInjection fluid induced damage

MACROSCALE MACROSCALE ISSUESISSUES

Reservoir HeterogeneityReservoir Heterogeneity

Permeability ContrastsPermeability Contrasts

Reservoir ContinuityReservoir Continuity

Natural FracturesNatural Fractures

Natural Fractures Parallel to the Natural Fractures Parallel to the Line of FlowLine of Flow

Natural Fractures Perpendicular Natural Fractures Perpendicular to the Line of Flowto the Line of Flow

Directional Permeability Trends Directional Permeability Trends Can Give Similar PerformanceCan Give Similar Performance

Presence of Sealing FaultsPresence of Sealing Faults

Microscale IssuesMicroscale IssuesPrimarily Dominated by Wettability Primarily Dominated by Wettability

EffectsEffects

What is Wettability?What is Wettability?Preferential Attraction of a fluid to a solid Preferential Attraction of a fluid to a solid

surface in the presence of one or more surface in the presence of one or more other immiscible fluidsother immiscible fluids

Wettability TypesWettability TypesWater WetWater WetOil WetOil WetNeutral WetNeutral WetMixed WetMixed WetSpotted WetSpotted Wet

Impact of Wettability on Relative Impact of Wettability on Relative Permeability to Water and OilPermeability to Water and Oil

Relative PermeabilityRelative Permeability

Water Saturation - Fraction

Swi 10%Crossover 22% SwKrw = 0.88

Swi approx 25%Crossover approx 68% Krw = 0.08

Typical Relative Typical Relative Permeability Curve Permeability Curve

Configurations for Other Configurations for Other Wettability TypesWettability Types

Neutral Wet FormationsNeutral Wet Formations

Swi 10-20%Crossover around 50%Krw = 0.45

Mixed WettabilityMixed WettabilityA fairly common wettability type in which A fairly common wettability type in which

tight microporosity is water saturated and tight microporosity is water saturated and water wet, while oil saturated macropores water wet, while oil saturated macropores are oil wetare oil wet

Typical Mixed Wettability Typical Mixed Wettability Relative Permeability CurvesRelative Permeability Curves

Swi = 40%Crossover approx 55%Krw = 0.70

Spotted/Dalmatian WettabilitySpotted/Dalmatian WettabilitySwi = 22%Crossover = 59%Krw = 0.28

General Impact of Wettability on General Impact of Wettability on Rel PermRel Perm

FactorFactor WaterWaterWetWet

Oil WetOil Wet Neutral Neutral WetWet

Mixed WetMixed Wet

SwiSwi >15%>15% <15%<15% 10-20%10-20% >15%>15%

CrossoverCrossoverPointPoint

> 50% Sw> 50% Sw < 50% Sw< 50% Sw Approx Approx 50% Sw50% Sw

< 50% Sw< 50% Sw

Krw at SorKrw at Sor <0.2<0.2 >0.5>0.5 0.2-0.50.2-0.5 >0.5>0.5

Swi as Swi as F(Perm)F(Perm)

StrongStrong NoneNone WeakWeak StrongStrong

SorwSorw >20%>20% >20%>20% <25%<25% <25%<25%

Specific Impact of Specific Impact of Wettability on Wettability on

Waterflood Waterflood PerformancePerformance

Concept of ‘Mobility Ratio’Concept of ‘Mobility Ratio’

M = x Krw

w x K roMobility Ratio

Viscosity ofDisplaced Phase

Rel Perm ofDisplacingPhase

Viscosity ofDisplacing Phase

Rel Perm ofDisplacedPhase

Favorable vs. Unfavorable Favorable vs. Unfavorable Mobility RatioMobility Ratio

Factors Improving MobilityFactors Improving Mobility

M = x Krw

w x K ro

Low Oil Visc Low Krw / Krg

High Displacing Phase Visc

High Kro

Example – Waterflood in a Example – Waterflood in a Favorable Mobility System Favorable Mobility System

(M=0.5)(M=0.5)

Example – Waterflood in a Example – Waterflood in a Unfavorable Mobility System Unfavorable Mobility System

(M=20)(M=20)

Wettability and Mobility Wettability and Mobility EffectsEffects

Since relative permeability endpoint values Since relative permeability endpoint values are strongly impacted by Wettability, oil vs. are strongly impacted by Wettability, oil vs. water wet systems may have order of water wet systems may have order of magnitude difference in water-oil mobility magnitude difference in water-oil mobility ratioratio

Can substantially impact the economics of Can substantially impact the economics of a natural or induced water drive processa natural or induced water drive process

Residual Oil Saturations in Residual Oil Saturations in WaterfloodsWaterfloods

BREAKTHROUGH BREAKTHROUGH SorSorECONOMICECONOMIC Sor SorULTIMATEULTIMATE Sor Sor

Breakthrough SorBreakthrough SorRefers to residual oil saturation in the Refers to residual oil saturation in the

swept pattern at the time of swept pattern at the time of firstfirst water water productionproduction

INJ PROD

Economic SorEconomic SorRefers to residual oil saturation in the Refers to residual oil saturation in the

swept pattern at the time of swept pattern at the time of Maximum Maximum EconomicEconomic water cut water cut

INJ PROD

Ultimate (True) SorUltimate (True) SorRefers to residual oil saturation in the Refers to residual oil saturation in the

swept pattern if a near swept pattern if a near Infinite Infinite volume of volume of water were displaced to near zero oil cutwater were displaced to near zero oil cut

INJ PROD

Lab Measurements of SorLab Measurements of SorLab measurements of Sor generally give a Lab measurements of Sor generally give a

reasonable approximation of the reasonable approximation of the ULTIMATE Sor since usually a very large ULTIMATE Sor since usually a very large number of pore volumes of displacement number of pore volumes of displacement are conducted (10-100 typical)are conducted (10-100 typical)

Waterflooding in Differing Waterflooding in Differing Wettability ReservoirsWettability Reservoirs

Cumulative Pore Volumes of Injection

OIP Breakthrough Sor

Economic Sor

Ultimate Sor

Given this – What are the Given this – What are the Optimum Reservoir Wetting Optimum Reservoir Wetting

Conditions for a Waterflood?Conditions for a Waterflood?

This Depends Strongly on Which This Depends Strongly on Which Criteria Dominate the EvaluationCriteria Dominate the EvaluationUltimate oil recovery?Ultimate oil recovery?Speed of oil recovery?Speed of oil recovery?Ease of injection?Ease of injection?Minimum water cycling and Minimum water cycling and

disposal costs?disposal costs?

Residual Oil Saturation at Infinite Residual Oil Saturation at Infinite PV of Oil Displacement vs. PV of Oil Displacement vs.

WettabilityWettability

USBM Wettability Index-1.5 +1.50

Oil Wet Water WetNeutral

For Maximum Ease of Water For Maximum Ease of Water InjectionInjection

OilWet!

For Maximum Oil Recovery and For Maximum Oil Recovery and Lowest Residual Oil SaturationLowest Residual Oil Saturation

Neutral/MixedWet

For Most Rapid Oil Recovery and For Most Rapid Oil Recovery and Minimum Water ProductionMinimum Water Production

WaterWet!

Optimum Conditions?Optimum Conditions? In most cases, optimum economic In most cases, optimum economic

recovery efficiency is achieved when the recovery efficiency is achieved when the wetting condition is a strongly water wet as wetting condition is a strongly water wet as possiblepossible

Does This Mean if my Reservoir Does This Mean if my Reservoir is is NOT NOT Water Wet Waterflooding Water Wet Waterflooding

Will Will NOTNOT be Economic? be Economic?

To Flood?

To Not to Flood?

Many Successful Waterfloods Many Successful Waterfloods have been Conducted in Oil Wet have been Conducted in Oil Wet

and Mixed Wet Reservoirsand Mixed Wet ReservoirsOverall economic benefit may be less than Overall economic benefit may be less than

if the reservoir had been strongly water if the reservoir had been strongly water wet, but may still represent substantial wet, but may still represent substantial improvement over straight primary improvement over straight primary depletiondepletion

Interfacial Tension Interfacial Tension ForcesForces

Interaction of Wettability, Interaction of Wettability, Interfacial Tension and Interfacial Tension and Pore Size DistributionPore Size Distribution

Pc=2(Cosr

Interfacial Tension Interfacial Tension

Water - Oil (0.2-40 dyne/cm)Water - Oil (0.2-40 dyne/cm)Gas-Water (2-70 dyne/cm)Gas-Water (2-70 dyne/cm)Gas-Oil (0-60 dyne/cm)Gas-Oil (0-60 dyne/cm)F(composition (H2S, CO2), temperature F(composition (H2S, CO2), temperature

and pressure)and pressure)

Global Effect of IFT on Water-Oil Relative Global Effect of IFT on Water-Oil Relative Permeability/Sor – IFT Dominated SystemPermeability/Sor – IFT Dominated System

Water Saturation - FractionWater Saturation - Fraction

KroKro

KrwKrw

KroKro

KrwKrw

KroKro KrwKrw

Why do some low IFTWhy do some low IFTinjections not result in injections not result in

large incremental oil recovery?large incremental oil recovery?

Sor – IFT Effects in Water Wet Sor – IFT Effects in Water Wet RockRock

Pore Throat Diameter Profile - Microns

Microporosity is WaterSaturated in WW Rock

A Given IFT Level AllowsAccess to Pore Throats LargerThan a Certain Size AccessibleInaccessible

ount AccessibleInaccessible

Sor – IFT Effects in Oil Wet RockSor – IFT Effects in Oil Wet Rock

Microporosity is OilSaturated in OW Rock

Small Sw Generally is In Center of Macropores in OW Rock

Sor – IFT Effects in Oil Wet RockSor – IFT Effects in Oil Wet Rock

Non Uniform Pore System – Non Uniform Pore System – Macropore DominatedMacropore Dominated

Non Uniform Pore System – Non Uniform Pore System – Micropore DominatedMicropore Dominated

The dominance of Wettability, The dominance of Wettability, IFT or Mobility controls recovery IFT or Mobility controls recovery

and injectivityand injectivity

Results of a Constant IFT Flood Results of a Constant IFT Flood in the Reservoir Dominated by in the Reservoir Dominated by

IFT EffectsIFT Effects

Mobility EffectsMobility Effects

Waterflood RequirementsWaterflood Requirements

#1 Suitable Reservoir

#2 Water!!!

Typical Water SourcesTypical Water SourcesProduced water(s) (Native and non native Produced water(s) (Native and non native

to formation)to formation)Surface water (Rivers, lakes, etc)Surface water (Rivers, lakes, etc)Shallow ground waterShallow ground waterWaste water streamsWaste water streamsOften a mixture of some of the aboveOften a mixture of some of the above

Surface Water

Shallow Aquifer

ProducingFormation

Deep Aquifer

Surface Water - Direct Intake

Surface Water

Shallow Aquifer

ProducingFormation

Deep Aquifer

Surface Water - Infiltration Gallery

Surface Water

Shallow Aquifer

ProducingFormation

Deep Aquifer

Shallow Aquifer

Surface Water

Shallow Aquifer

ProducingFormation

Deep Aquifer

Formation Water

Surface Water

Shallow Aquifer

ProducingFormation

Deep Aquifer

Injection Water Quality IssuesInjection Water Quality IssuesSufficient volume for future requirements?Sufficient volume for future requirements?Reliable year round source?Reliable year round source?Total suspended solids content (TSS)Total suspended solids content (TSS)Oil and Grease Content (OGC)Oil and Grease Content (OGC)Total dissolved solids content (TDS)Total dissolved solids content (TDS)Scaling indexesScaling indexesSpecific ionic compositionSpecific ionic composition

Waterflood Waterflood Screening and Screening and

Evaluation ProcessEvaluation Process

General ProcessGeneral Process

MacroscaleMacroscaleScreeningScreening

MicroscaleMicroscaleScreeningScreening

WaterWater SourceSource

AndAnd QualityQualityEvaluationEvaluation

Simulation,Simulation,ImplementationImplementation

Typical Screening Studies Conducted on Typical Screening Studies Conducted on a Lab Basis (Microscale and Water a Lab Basis (Microscale and Water

Quality Sections)Quality Sections) Pore size distributionPore size distribution WettabilityWettability Capillary pressureCapillary pressure Relative PermeabilityRelative Permeability Interfacial TensionInterfacial Tension Water qualityWater quality Injectivity studiesInjectivity studies Stimulation StudiesStimulation Studies Conformance controlConformance control

Pore Size DistributionPore Size DistributionMercury injection studiesMercury injection studiesThin section studiesThin section studies Image analysis studiesImage analysis studies

WettabilityWettabilityContact AngleContact AngleAmott/Combined Amott-USBM methodAmott/Combined Amott-USBM method

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Water Saturation, fraction of PV

illary

Capillary PressureCapillary PressurePorous PlatePorous PlateCentrifuge methodsCentrifuge methodsAir-Mercury conversionAir-Mercury conversion

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Oil Saturation, fraction of PV

illary

Relative PermeabilityRelative PermeabilitySteady StateSteady StateUnsteady StateUnsteady StateReservoir/Ambient conditionReservoir/Ambient condition

Gas/Oil Relative Permeability Profile

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Gas Saturation (fraction)

KrgKro

Interfacial TensionInterfacial TensionDunoue RingDunoue RingSpinning DropSpinning DropDrop PendantDrop Pendant

Water QualityWater QualityCompositionCompositionSuspended solidsSuspended solidsOil and grease contentOil and grease contentBacterial content/typingBacterial content/typingpHpH

Injectivity StudiesInjectivity StudiesWater sensitivityWater sensitivityCritical salinityCritical salinityCritical FiltrationCritical FiltrationPhase trappingPhase trappingBacterial growthBacterial growth

StimulationStimulationAcidization for scale removalAcidization for scale removalSolvent treatments (paraffin's, Solvent treatments (paraffin's,

asphaltenes, oil blocks, etc)asphaltenes, oil blocks, etc)Fracture optimizationFracture optimizationNear wellbore wettability alteration Near wellbore wettability alteration

evaluationsevaluations

Conformance ControlConformance ControlWater diversion and shutoff treatmentsWater diversion and shutoff treatments

GelsGelsPolymersPolymersRelative permeability modifiersRelative permeability modifiers

ConclusionsConclusions

ConclusionsConclusions Waterflooding can result in significant additional Waterflooding can result in significant additional

incremental oil recovery in many reservoir incremental oil recovery in many reservoir situationssituations

Not all reservoirs are prime waterflood Not all reservoirs are prime waterflood candidatescandidates

Macroscale features may control the Macroscale features may control the effectiveness of a waterfloodeffectiveness of a waterflood

Mobility dominates microscale sweep efficiencyMobility dominates microscale sweep efficiency A detailed protocol for evaluation has been A detailed protocol for evaluation has been

presentedpresented

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