The Mystery of The Mystery of Capillary PressureCapillary Pressure

April 2005April 2005

Presentation SummaryPresentation Summary What is capillary pressure and what causes it?What is capillary pressure and what causes it? Why is understanding capillary pressure Why is understanding capillary pressure

important to reservoir optimization?important to reservoir optimization? Situation of capillary equilibrium and non-Situation of capillary equilibrium and non-

equilibriumequilibrium How capillary pressure can work for or against How capillary pressure can work for or against

us in oil and gas production operationsus in oil and gas production operations How to we measure and understand capillary How to we measure and understand capillary

pressurepressure

WHAT IS WHAT IS CAPILLARY CAPILLARY PRESSURE?PRESSURE?

Pc = 2 * Pc = 2 * σσ * cos * cos θθ / r / r

The strength of the Interface The strength of the Interface between two fluids is Measured by between two fluids is Measured by

the ‘Interfacial Tension’the ‘Interfacial Tension’

Typical Interfacial Tension ValuesTypical Interfacial Tension Values

Air – Water = 70 dyne/cm (mN.m)Air – Water = 70 dyne/cm (mN.m)Air – mineral oil = 25-30 dyne/cmAir – mineral oil = 25-30 dyne/cmAir – mercury = 470 dyne/cmAir – mercury = 470 dyne/cmThe The lowerlower the IFT – the closer the two the IFT – the closer the two

phases are to phases are to ‘miscibly’‘miscibly’ blending blendingLow IFT considered to be <0.01 dyne/cmLow IFT considered to be <0.01 dyne/cm

Typical Reservoir Fluid Interfacial Typical Reservoir Fluid Interfacial Tension ValuesTension Values

Water – Gas (2000 psi, 100 C, 85% C1) – Water – Gas (2000 psi, 100 C, 85% C1) – 30-40 dyne/cm30-40 dyne/cm

Water – CO2 Gas (2000 psi, 100 C) - < 2 Water – CO2 Gas (2000 psi, 100 C) - < 2 dyne/cmdyne/cm

Water – Live Oil - typically 5-25 dyne/cmWater – Live Oil - typically 5-25 dyne/cmGas – Oil – typically 1-30 dyne/cmGas – Oil – typically 1-30 dyne/cmAdditional of surfactants or miscible Additional of surfactants or miscible

solvents can radically lower IFTsolvents can radically lower IFT

Common Methods of Interfacial Common Methods of Interfacial Tension MeasurementTension Measurement

Drop PendantDrop PendantSpinning dropSpinning dropDunoue RingDunoue Ring

The Interaction of the Interface Will The Interaction of the Interface Will be Controlled by the Preferential be Controlled by the Preferential

Surface WettabilitySurface Wettability

The Interaction of the Interface Will The Interaction of the Interface Will be Controlled by the Preferential be Controlled by the Preferential

Surface WettabilitySurface Wettability

The Interaction of the Interface Will The Interaction of the Interface Will be Controlled by the Preferential be Controlled by the Preferential

Surface WettabilitySurface Wettability

The Concept of ‘Capillary The Concept of ‘Capillary Curvature’Curvature’

cRPc 1

Capillary Pressure Effects in a Capillary Pressure Effects in a Capillary TubeCapillary Tube

The Size of the Characteristic The Size of the Characteristic Radius Will be a Function ofRadius Will be a Function of

The size of the capillary (the smaller the The size of the capillary (the smaller the capillary, the smaller the size of the capillary, the smaller the size of the characteristic radius)characteristic radius)

The interfacial tension between the two The interfacial tension between the two fluids (the higher the IFT, the stiffer the fluids (the higher the IFT, the stiffer the interface and the smaller the amount of interface and the smaller the amount of the characteristic radius)the characteristic radius)

ThereforeThereforeAs the size of the capillary decreases, the As the size of the capillary decreases, the

radius of curvature decreases and hence radius of curvature decreases and hence the value of the capillary pressure the value of the capillary pressure increasesincreases

As the IFT between the fluids increases As the IFT between the fluids increases the stiffness of the interface increases and the stiffness of the interface increases and hence the capillary pressure increaseshence the capillary pressure increases

In Nature, the ‘Suction’ Effect of Capillary In Nature, the ‘Suction’ Effect of Capillary Pressure is Exactly Balanced by Gravity in Pressure is Exactly Balanced by Gravity in an Equilibrium Situation With no Imposed an Equilibrium Situation With no Imposed

External Pressure GradientsExternal Pressure Gradients

ghP cHydrostati

Thus in Capillaries of Differing Thus in Capillaries of Differing sizessizes

How do we Translate How do we Translate These Principles to These Principles to

a Oil or Gas a Oil or Gas Reservoir Situation?Reservoir Situation?

A Reservoir Pore System Can be Considered to A Reservoir Pore System Can be Considered to be a Network of ‘Capillary’ Tubes of Varying Sizes be a Network of ‘Capillary’ Tubes of Varying Sizes

and Degrees of Interconnectivenessand Degrees of Interconnectiveness

A Reservoir Pore System Can be Considered to A Reservoir Pore System Can be Considered to be a Network of ‘Capillary’ Tubes of Varying Sizes be a Network of ‘Capillary’ Tubes of Varying Sizes

and Degrees of Interconnectivenessand Degrees of Interconnectiveness

The Hydrostatic Portion of any Two The Hydrostatic Portion of any Two (or more) Phase Portion of a (or more) Phase Portion of a

Reservoir Can be Expressed AsReservoir Can be Expressed As

ghP cHydrostati

Therefore we can Also Say ThatTherefore we can Also Say That

chcap RghP 1)(

Thus in a Static Capillary Thus in a Static Capillary Equilibrium Situation, Equilibrium Situation,

Hydrostatic Gravitational Hydrostatic Gravitational Forces Always Exactly Forces Always Exactly Balance the Capillary Balance the Capillary

Pressure ForcesPressure Forces

This is too SayThis is too Say

CA

PILLAR

Y FOR

CES

GR

AVI

TY F

OR

CES

The Concept of a Capillary The Concept of a Capillary Transition ZoneTransition Zone

The Concept of a Capillary The Concept of a Capillary Transition ZoneTransition Zone

Water Contact – Location in the Reservoir Where aFinite Free Gas or Oil Saturation Begins to be Apparent

The Concept of a Capillary The Concept of a Capillary Transition ZoneTransition Zone

The Concept of a Capillary The Concept of a Capillary Transition ZoneTransition Zone

In a Low Permeability Reservoir the In a Low Permeability Reservoir the Pores/Pore Throats Are SmallPores/Pore Throats Are Small

This Equates to a Network of Very Fine This Equates to a Network of Very Fine Capillaries and Hence ‘High’ Capillary Capillaries and Hence ‘High’ Capillary

PressurePressure

In a High Permeability Reservoir In a High Permeability Reservoir the Pores/Pore Throats Are Largerthe Pores/Pore Throats Are Larger

This Equates to a Network of Larger Capillaries This Equates to a Network of Larger Capillaries and Hence ‘Lower’ Capillary Pressure at a Given and Hence ‘Lower’ Capillary Pressure at a Given

Height Above the Free Water ContactHeight Above the Free Water Contact

In a Reservoir, The Capillary Pressure is In a Reservoir, The Capillary Pressure is Controlled by the Characteristic Curvature. Controlled by the Characteristic Curvature.

Unlike a Capillary Tube Both Phases Exist at the Unlike a Capillary Tube Both Phases Exist at the Same Time in a Given Pore LocationSame Time in a Given Pore Location

In a Reservoir, The Capillary Pressure is In a Reservoir, The Capillary Pressure is Controlled by the Characteristic Curvature as Controlled by the Characteristic Curvature as

Unlike a Capillary Tube Both Phases Exist at the Unlike a Capillary Tube Both Phases Exist at the Same Time in a Given Pore LocationSame Time in a Given Pore Location

In a Reservoir, The Capillary Pressure is In a Reservoir, The Capillary Pressure is Controlled by the Characteristic Curvature as Controlled by the Characteristic Curvature as

Unlike a Capillary Tube Both Phases Exist at the Unlike a Capillary Tube Both Phases Exist at the Same Time in a Given Pore LocationSame Time in a Given Pore Location

The Concept of a Capillary The Concept of a Capillary Transition ZoneTransition Zone

The Concept of a Capillary The Concept of a Capillary Transition ZoneTransition Zone

The Concept of a ‘Capillary The Concept of a ‘Capillary Pressure Curve’Pressure Curve’

A graphical relationship that relates the A graphical relationship that relates the apparent capillary pressure to the average apparent capillary pressure to the average water saturation in a given (assumed to be water saturation in a given (assumed to be homogeneous) pore systemhomogeneous) pore system

Typical Water-Gas Capillary Typical Water-Gas Capillary Pressure CurvePressure Curve

Typical Water-Gas Capillary Typical Water-Gas Capillary Pressure CurvePressure Curve

Typical Water-Gas Capillary Typical Water-Gas Capillary Pressure CurvePressure Curve

COMMON CAPILLARY COMMON CAPILLARY PRESSURE PRESSURE

DETERMINATION METHODSDETERMINATION METHODS

Common Capillary Pressure Common Capillary Pressure Determination MethodsDetermination Methods

Porous PlatePorous PlateClean StateClean StateNative StateNative State

CentrifugeCentrifugeClean StateClean StateNative StateNative State

Mercury InjectionMercury Injection

Porous Plate MethodPorous Plate MethodUses a ceramic wetted plate Uses a ceramic wetted plate Plate is permeable to only the wetting Plate is permeable to only the wetting

phase in the porous media being phase in the porous media being evaluated up to a certain ‘breakdown’ evaluated up to a certain ‘breakdown’ pressure level (typically 1000-1500 kPa)pressure level (typically 1000-1500 kPa)

Two methods, single plate (capable of full Two methods, single plate (capable of full reservoir conditions) and bulk porous plate reservoir conditions) and bulk porous plate (non reservoir conditions)(non reservoir conditions)

SINGLE POROUS PLATE SINGLE POROUS PLATE METHODMETHOD

Porous Plate

Core Sample atMaximum

WettingPhase

Saturation

Injection Head

NonWetPhs

Constant P Drive

SINGLE POROUS PLATE SINGLE POROUS PLATE METHODMETHOD

Porous Plate

Core Sample atMaximum

WettingPhase

Saturation

Injection Head

NonWetPhs

Constant P Drive

SINGLE POROUS PLATE SINGLE POROUS PLATE METHODMETHOD

Porous Plate

Core Sample atMaximum

WettingPhase

Saturation

Injection Head

NonWetPhs

Constant P Drive

SINGLE POROUS PLATE SINGLE POROUS PLATE METHODMETHOD

Porous Plate

Core Sample atMaximum

WettingPhase

Saturation

Injection Head

NonWetPhs

Constant P Drive

SINGLE POROUS PLATE SINGLE POROUS PLATE METHODMETHOD

Porous Plate

Core Sample atMaximum

WettingPhase

Saturation

Injection Head

NonWetPhs

Constant P Drive

SINGLE POROUS PLATE SINGLE POROUS PLATE METHODMETHOD

Porous Plate

Core Sample atMaximum

WettingPhase

Saturation

Injection Head

NonWetPhs

Constant P Drive

Data AnalysisData Analysis

Advantages and Disadvantages of Advantages and Disadvantages of the Single Plug Porous Plate the Single Plug Porous Plate

MethodMethod

PROSPROS Can stress samplesCan stress samples Can use native state Can use native state

core materialcore material Can be conducted in Can be conducted in

conjunction with conjunction with electrical property electrical property measurementsmeasurements

ConsCons Slow for low perm Slow for low perm

samplessamples Increased expenseIncreased expense Maximum 1000-1500 Maximum 1000-1500

kPa capillary pressure kPa capillary pressure possiblepossible

Not suitable for Not suitable for samples less than 1-5 samples less than 1-5 mDmD

SINGLE POROUS PLATE SINGLE POROUS PLATE SYSTEMSYSTEM

BULK POROUS PLATE METHODBULK POROUS PLATE METHOD

BULK POROUS PLATE

QUICK RELEASE PRESSURE SEAL COVER

BULK POROUS PLATE METHODBULK POROUS PLATE METHOD

BULK POROUS PLATE

QUICK RELEASE PRESSURE SEAL COVER

BULK POROUS PLATE METHODBULK POROUS PLATE METHOD

BULK POROUS PLATE

QUICK RELEASE PRESSURE SEAL COVER

BULK POROUS PLATE METHODBULK POROUS PLATE METHOD

BULK POROUS PLATE

QUICK RELEASE PRESSURE SEAL COVER

BULK POROUS PLATE CELLBULK POROUS PLATE CELL

Advantages and Disadvantages of Advantages and Disadvantages of the Bulk Porous Plate Methodthe Bulk Porous Plate Method

PROSPROS Can use native state core Can use native state core

materialmaterial Can be conducted in Can be conducted in

conjunction with electrical conjunction with electrical property measurementsproperty measurements

Relatively inexpensiveRelatively inexpensive

ConsCons Slow for low perm Slow for low perm

samplessamples Maximum 1000-1500 kPa Maximum 1000-1500 kPa

capillary pressure capillary pressure possiblepossible

Not suitable for samples Not suitable for samples less than 1-5 mDless than 1-5 mD

Test proceeds at the rate Test proceeds at the rate of the lowest permeability of the lowest permeability samplesample

MODIFIED BULK POROUS PLATE MODIFIED BULK POROUS PLATE METHODMETHOD

BULK POROUS PLATE

QUICK RELEASE PRESSURE SEAL COVER

MODIFIED BULK POROUS PLATE MODIFIED BULK POROUS PLATE CELLCELL

Advantages and Disadvantages of Advantages and Disadvantages of the Bulk Porous Plate Methodthe Bulk Porous Plate Method

PROSPROS Can use native state core Can use native state core

materialmaterial Can be conducted in Can be conducted in

conjunction with electrical conjunction with electrical property measurementsproperty measurements

Relatively inexpensiveRelatively inexpensive No need to remove No need to remove

samples from system samples from system resulting in less sample resulting in less sample disturbance and grain disturbance and grain lossloss

ConsCons Slow for low perm Slow for low perm

samplessamples Maximum 1000-1500 kPa Maximum 1000-1500 kPa

capillary pressure capillary pressure possiblepossible

Not suitable for samples Not suitable for samples less than 1-5 mDless than 1-5 mD

Test proceeds at the rate Test proceeds at the rate of the lowest permeability of the lowest permeability samplesample

CENTRIFUGE METHODSCENTRIFUGE METHODS

Centrifuge MethodsCentrifuge MethodsUse applied centrifugal force induced by Use applied centrifugal force induced by

rapid rotation of the core sample to rapid rotation of the core sample to generate the capillary pressure forcegenerate the capillary pressure force

Non linear capillary pressure and Non linear capillary pressure and saturation profile is generated using this saturation profile is generated using this methodmethod

Centrifuge SystemCentrifuge System

Capillary Pressure Induced by Capillary Pressure Induced by RotationRotation

),,,( 2 SRcap LLfP

Core Sample

Invading Fluid

Base PrecisionCollection Pipette

Top PrecisionCollection Pipette

Core Sample

Invading Fluid

Core Sample

Invading Fluid

Core Sample

Invading Fluid

Core Sample

Invading Fluid

Generation of the Capillary Generation of the Capillary Pressure CurvePressure Curve

Initial Conditions100% Water Saturation

Generation of the Capillary Generation of the Capillary Pressure CurvePressure Curve

Endface Pcap

‘Average’ Sw

Endface Sw

Generation of the Capillary Generation of the Capillary Pressure CurvePressure Curve

Endface Pcap‘A

verage’ Sw

Endface Sw

Core Sample

Invading Fluid

Core Sample

Invading Fluid

Core Sample

Invading Fluid

Core Sample

Invading Fluid

Generation of the Capillary Pressure Curve Generation of the Capillary Pressure Curve – Restored State Secondary Drainage– Restored State Secondary DrainageInitial ConditionsAt Initial Reservoir Water Saturation

Generation of the Capillary Pressure Curve Generation of the Capillary Pressure Curve – Restored State Secondary Drainage– Restored State Secondary Drainage

Generation of the Capillary Pressure Curve Generation of the Capillary Pressure Curve – Restored State Secondary Drainage– Restored State Secondary Drainage

Core Sample

Invading Fluid

Core Sample

Invading Fluid

Core Sample

Invading Fluid

Core Sample

Invading Fluid

Generation of the Capillary Pressure Curve Generation of the Capillary Pressure Curve – Restored State Imbibition Drainage– Restored State Imbibition Drainage

Generation of the Capillary Pressure Curve Generation of the Capillary Pressure Curve – Restored State Imbibition Drainage– Restored State Imbibition Drainage

The Combined Amott/USBM The Combined Amott/USBM Wettability TestWettability Test

Most common and accurate method of Most common and accurate method of reservoir wettability determinationreservoir wettability determination

Can use dead oil & brine Can use dead oil & brine Useful for distinguishing type and degree Useful for distinguishing type and degree

of wettability preferenceof wettability preferenceUses the principle of Uses the principle of capillarycapillary

thermodynamics to infer thermodynamics to infer wettabilitywettability

Basis of the MethodBasis of the MethodArea under a capillary pressure – water Area under a capillary pressure – water

saturation curve provides a representation saturation curve provides a representation of the relative amount of ‘work’ required to of the relative amount of ‘work’ required to displace a fluid into a porous mediadisplace a fluid into a porous media

Example – strongly water wet rocks will Example – strongly water wet rocks will readily spontaneously imbibe water and readily spontaneously imbibe water and absorb water under applied capillary absorb water under applied capillary pressure much easier than the oil phasepressure much easier than the oil phase

Combined Amott/USBM MethodCombined Amott/USBM Method

BRINE STATICIMBIBITION

OIL STATICIMBIBITION

Amott Wettability IndexAmott Wettability Index

Total

eousSpon

Water

Water

VV

Water tan

Total

eousSpon

Oil

Oil

VV

Oil tan

Amott Wettability IndicesAmott Wettability IndicesWaterWater

Near Zero – oil/neutral wet or tightNear Zero – oil/neutral wet or tightNear 1 – strongly water wetNear 1 – strongly water wet

OilOilNear zero – water/neutral wet or tightNear zero – water/neutral wet or tightNear 1 – strongly oil wetNear 1 – strongly oil wet

USBM Wettability IndexUSBM Wettability Index

2

1logAAUSBM Index

USBM Wettability IndexUSBM Wettability Index

2

1logAAUSBM Index

-0.1 to +0.1Neutral Wet

USBM Wettability IndexUSBM Wettability Index

2

1logAAUSBM Index

+0.1 to +0.3Moderately Water Wet

-0.1 to -0.3Moderately Oil Wet

USBM Wettability IndexUSBM Wettability Index

2

1logAAUSBM Index

Greater Than +0.3Strongly Water Wet

Less than -0.3Strongly Oil Wet

Example – Strongly Water Wet Example – Strongly Water Wet RockRock

2

1logAAUSBM Index

Example – Strongly Oil Wet RockExample – Strongly Oil Wet Rock

2

1logAAUSBM Index

Example – Neutral Wet RockExample – Neutral Wet Rock

2

1logAAUSBM Index

Example – Mixed Wet RockExample – Mixed Wet Rock

2

1logAAUSBM Index

Mercury Injection Capillary Mercury Injection Capillary PressurePressure

Most common capillary pressure determination Most common capillary pressure determination methodmethod

Uses clean dry core samples 2.5 x 2.5 cm in Uses clean dry core samples 2.5 x 2.5 cm in diameter/lengthdiameter/length

Mercury approximates the non wetting phase, air Mercury approximates the non wetting phase, air approximates the wetting phaseapproximates the wetting phase

Very high pressures of over 400 MPa (60,000 Very high pressures of over 400 MPa (60,000 psi) are used to intrude mercury into even the psi) are used to intrude mercury into even the very smallest (0.001 micron) poresvery smallest (0.001 micron) pores

Very useful for all different permeability ranges Very useful for all different permeability ranges of rock from micro to macro Darcy formationsof rock from micro to macro Darcy formations

Mercury Injection SystemMercury Injection System

Mercury Injection SystemMercury Injection System

Typical Computerized Air-Mercury Typical Computerized Air-Mercury Capillary Pressure Measurement Capillary Pressure Measurement

SystemSystem

Mercury Capillary PressureMercury Capillary PressureBecause the IFT between air and mercury Because the IFT between air and mercury

and the contact angle of mercury and rock and the contact angle of mercury and rock is precisely known, the primary use of Hg is precisely known, the primary use of Hg capillary pressure data is to map out the capillary pressure data is to map out the pore size distribution of specific reservoir pore size distribution of specific reservoir flow faciesflow facies

Pore Scale Intrusion VisualizationPore Scale Intrusion Visualization

Pore Throat ClassificationsPore Throat Classifications

MACROPORES MACROPORES - >3 - >3 MICRONS DIAMETERMICRONS DIAMETER

MESOPORESMESOPORES – 1-3 – 1-3 MICRONS DIAMETERMICRONS DIAMETER

MICROPORESMICROPORES – <1 MICRON – <1 MICRON

Pore Scale Intrusion VisualizationPore Scale Intrusion Visualization

pC rfP ,,

ThereforeThereforeMeasurement of specific volume of Measurement of specific volume of

mercury injected into the core at a given mercury injected into the core at a given applied pressure (Pc) allows us to applied pressure (Pc) allows us to determine the specific value of the pore determine the specific value of the pore throats being penetrated by the invading throats being penetrated by the invading mercury and the relative volume fraction of mercury and the relative volume fraction of the pore system that is ‘accessed’ by the pore system that is ‘accessed’ by these pore throatsthese pore throats

Thus the Raw Cap Pressure DataThus the Raw Cap Pressure Data

High Perm

Mid Perm

Low Perm

Thus For Our Three Example Thus For Our Three Example CasesCases

00.050.1

0.150.2

0.250.3

0.350.4

0.001 0.1 10 1000

Pore Throat Diameter - Microns

Volu

me

Frac

tion

of P

ore

syst

em High PermMid PermLow Perm

Pore Size Distribution Data Pore Size Distribution Data Invaluable forInvaluable for

Rock type classificationRock type classificationFlow unit typingFlow unit typingEstimation of residual and initial Estimation of residual and initial

saturationssaturationsPrediction of potential for various potential Prediction of potential for various potential

types of formation damagetypes of formation damageFraction split of ‘effective’ and ‘ineffective’ Fraction split of ‘effective’ and ‘ineffective’

porosity in a pore systemporosity in a pore system

Conversion of Mercury Capillary Conversion of Mercury Capillary Pressure Data to reservoir Pressure Data to reservoir

ConditionsConditionsRequires a good knowledge of exact fluid-Requires a good knowledge of exact fluid-

fluid IFT between the reservoir fluids and fluid IFT between the reservoir fluids and the wettability of the reservoir for accurate the wettability of the reservoir for accurate conversionconversion

Common conversion of Hg-air data to;Common conversion of Hg-air data to;Water-gasWater-gasWater-oilWater-oil

Capillary Pressure Conversion Capillary Pressure Conversion FactorFactor

airHgairhg

RFRFconvPc

coscos

Typical Conversion Factors to Gas-Typical Conversion Factors to Gas-Water and Gas-OilWater and Gas-Oil

IFT THETACorrection

Factor

Dyne/cm Degrees  

     

70 0 8.578

70 30 7.429

70 60 4.289

70 90 0.000

70 120 -4.289

70 150 -7.429

70 180 -8.578

IFT THETACorrection

Factor

Dyne/cm Degrees  

     

25 0 24.019

25 30 20.801

25 60 12.010

25 90 0.000

25 120 -12.010

25 150 -20.801

25 180 -24.019

Typical Air-Mercury Capillary Pressure Typical Air-Mercury Capillary Pressure Conversion Factor Data as a Function of IFT Conversion Factor Data as a Function of IFT

and Wettabilityand Wettability

-60.000

-40.000

-20.000

0.000

20.000

40.000

60.000

Reservoir Oil/Gas - Water Contact Angle - Degrees

Hg -

Air P

c Co

rrec

tion

fact

or

IFT= 70 dynes/cm

IFT = 50 dynes/cm

IFT = 30 dynes/cm

IFT = 20 dynes/cm

IFT= 10 dynes/cm

Ways in Which we Use Cap Ways in Which we Use Cap Pressure on a Reservoir ScalePressure on a Reservoir Scale

Initial saturation and transition zone Initial saturation and transition zone determinationsdeterminations

Effect of cap pressure on residual and Effect of cap pressure on residual and trapped saturationstrapped saturations

Cap pressure related formation damage Cap pressure related formation damage issuesissues

Countercurrent imbibition effects induced Countercurrent imbibition effects induced by cap pressure in non-hydrostatic by cap pressure in non-hydrostatic equilibrium situationsequilibrium situations

Typical Water-Gas Capillary Typical Water-Gas Capillary Pressure CurvePressure Curve

Swir

Transition ZoneWater & Oil Produced

Water Free Production

Water Based Phase TrappingWater Based Phase Trapping

Water Saturation

Water Saturation

Cap

illar

y P

ress

ure

Rel

ativ

e P

erm

Water Based Phase TrappingWater Based Phase Trapping

Water Saturation

Water Saturation

Cap

illar

y P

ress

ure

Rel

ativ

e P

erm

Water Based Phase TrappingWater Based Phase Trapping

Water Saturation

Water Saturation

Cap

illar

y P

ress

ure

Rel

ativ

e P

erm

Large Vertical Standoff From Water-Oil Large Vertical Standoff From Water-Oil Contact in Water Wet FormationContact in Water Wet Formation

W-O CONTACT

Initial Saturation DistributionInitial Saturation DistributionControlled byControlled by

Capillary pressure characterCapillary pressure characterHeight above free water contactHeight above free water contact IFTIFTSurface WettabilitySurface Wettability

Hydrostatic Equilibrium Reservoirs Hydrostatic Equilibrium Reservoirs – Typical Sw Profile– Typical Sw Profile

W-O CONTACT

Hydrostatic Equilibrium Reservoirs Hydrostatic Equilibrium Reservoirs – High Permeability– High Permeability

W-O CONTACT

Hydrostatic Equilibrium Reservoirs Hydrostatic Equilibrium Reservoirs – Low Permeability– Low Permeability

W-O CONTACT

What About the Same Rock With What About the Same Rock With Variable Initial Wettability?Variable Initial Wettability?

W-O CONTACT

What About the Same Rock With What About the Same Rock With Variable Initial Wettability?Variable Initial Wettability?

W-O CONTACT

What About the Same Rock With What About the Same Rock With Variable Initial Wettability?Variable Initial Wettability?

W-O CONTACT

What About Rock and Wettability What About Rock and Wettability With Variable IFT?With Variable IFT?

W-O CONTACT

What About Rock and Wettability What About Rock and Wettability With Variable IFT?With Variable IFT?

W-O CONTACT

What About Rock and Wettability What About Rock and Wettability With Variable IFT?With Variable IFT?

ConclusionsConclusionsThe Mystery of Capillary The Mystery of Capillary

PressurePressureSolvedSolved

ConclusionsConclusionsCapillary pressure is an important variable Capillary pressure is an important variable

that controlsthat controlsOriginal distribution of fluids in a reservoirOriginal distribution of fluids in a reservoirDisplacement efficiency and residual Displacement efficiency and residual

saturationssaturationsUnderstanding of capillary pressure basics Understanding of capillary pressure basics

is essential for optimizing the performance is essential for optimizing the performance of a the reservoirof a the reservoir

ConclusionsConclusionsCapillary pressure is influenced by many Capillary pressure is influenced by many

phenomenaphenomenaPore size distributionPore size distributionReservoir wettabilityReservoir wettability Interfacial tensionInterfacial tensionOffset from free water contactOffset from free water contact

Reservoirs may or may not be in capillary Reservoirs may or may not be in capillary equilibrium – understanding this plays a equilibrium – understanding this plays a key factor in many situationskey factor in many situations

ConclusionsConclusionsA variety of methods are available for the A variety of methods are available for the

measurement of classical two phase measurement of classical two phase capillary pressurescapillary pressuresSingle cell porous plateSingle cell porous plateBulk porous plateBulk porous plateCentrifuge methodsCentrifuge methodsMercury injection (scaling methods)Mercury injection (scaling methods)

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