3- waterflooding

7/26/2019 3- Waterflooding

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WATERFLOODINGWATERFLOODING

Dr. Ir.Dr. Ir. DedyDedy KristantoKristanto,, M.ScM.Sc


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What is Waterflooding?What is Waterflooding?

2 Injection Water1 Oil Zone

InjectionWell

Separation andStorage Facilities

WaterInjection

Pump

Production Well

12


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What is Waterflooding?What is Waterflooding?

DescriptionDescription

Most widely used postMost widely used post--primary recovery methodprimary recovery method

Water injected in patterns or along periphery of reservoirWater injected in patterns or along periphery of reservoir

Mechanisms That Improve Recovery EfficiencyMechanisms That Improve Recovery Efficiency

Water driveWater drive

LimitationsLimitations

High oil viscosities / higher (more adverse) mobility ratiosHigh oil viscosities / higher (more adverse) mobility ratios

Heterogeneity such as stratification, permeabilityHeterogeneity such as stratification, permeabilitycontrast, and fracturing reduce sweep efficiencycontrast, and fracturing reduce sweep efficiency

ChallengesChallenges Poor compatibility between injected water and reservoirPoor compatibility between injected water and reservoir

may cause formation damagemay cause formation damage

Subsurface fluid control to divert injected water and shutSubsurface fluid control to divert injected water and shutoff undesirable produced fluidsoff undesirable produced fluids


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WaterfloodWaterflood MechanismsMechanisms

InjectorInjector ProducerProducer


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Flood Pattern RequirementsFlood Pattern Requirements

The pattern chosen for any injection project should:The pattern chosen for any injection project should:

1.1. Provide optimum oil production capacityProvide optimum oil production capacity

2.2. Provide sufficient injection capacity to support oilProvide sufficient injection capacity to support oilproductionproduction

3.3. Maximize oil recovery with minimum of waterMaximize oil recovery with minimum of waterproductionproduction

4.4. Use reservoir heterogeneity to best advantage andUse reservoir heterogeneity to best advantage andavoid factors which could reduce sweepavoid factors which could reduce sweepefficiencyefficiency

5.5. Use existing wells to minimize number of new wellsUse existing wells to minimize number of new wellsrequiredrequired

6. Be compatible with nearby operations6. Be compatible with nearby operations

Choose the best pattern based on first four characterist icsChoose the best pattern based on first four characterist ics and modifyand modify

chosen pattern to conform to fifth & sixthchosen pattern to conform to fifth & sixth -- goal should be efficientlygoal should be efficientlyprocessing reservoir, not minimizing cost to install waterfloodprocessing reservoir, not minimizing cost to install waterflood


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WaterfloodWaterflood Pattern CharacteristicsPattern Characteristics

Patterns are generally classified asPatterns are generally classified as normalnormal ororinvertedinverted

-- In normal waterflood patterns, the producing well is in theIn normal waterflood patterns, the producing well is in the

center of the patterncenter of the pattern

-- Inverted patterns have the injection well in the patternInverted patterns have the injection well in the patterncentercenter

Ratio of Required

Pattern Producers to Drilling PatternInjectors

4-Spot 2:1 TriangularSkewed 4-Spot 2:1 Square5-Spot 1:1 Square

7-Spot 1:2 TriangularInverted 7-Spot 2:1 Triangular9-Spot 1:3 Square

Inverted 9-Spot 3:1Square Direct Line Drive

1:1 RectangleStaggered Line Drive 1:1Offset linesof wells


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Line Drive PatternsLine Drive Patterns

a

d

Direct Line Drive

a

d

Staggered Line Drive

Efficiency of line drive patterns is generally highEfficiency of line drive patterns is generally high -- itit

increases as distance between the producing rowincreases as distance between the producing row

and injector row (d) increases, and distanceand injector row (d) increases, and distance

between adjacent producers (a) decreasesbetween adjacent producers (a) decreases


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55--Spot PatternSpot Pattern

A special case of the staggeredA special case of the staggeredline drive where d/a ratio is 0.5line drive where d/a ratio is 0.5

Most common pattern resultingMost common pattern resultingfrom primary well spacingfrom primary well spacing

Drilling pattern is squareDril ling pattern is square

Other pattern configurationsOther pattern configurationsgenerated by simply rearranginggenerated by simply rearranging

position of injectors & producersposition of injectors & producersflexibleflexible

Number of producers = number ofNumber of producers = number ofinjectorsinjectors

Highly conductive pattern sinceHighly conductive pattern sinceshortest flow path is a straightshortest flow path is a straightline between injector & producerline between injector & producer--

provides good sweep behavior

a

d

Normal 5-Spot Pattern

provides good sweep behavior


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99--Spot PatternSpot Pattern

Normal 9-Spot Inverted 9-Spot

Major advantage of the 9Major advantage of the 9--spot is the flexibil ityspot is the flexibil ity

-- Some other patterns are very difficult, and expensive toSome other patterns are very difficult, and expensive toconvert, and may require extensive infil l drill ingconvert, and may require extensive infil l drill ing

-- The inverted 9The inverted 9--spot can be revised to result in a 1:1spot can be revised to result in a 1:1injectorinjector--producer ratio patter, either 5producer ratio patter, either 5--spot or l ine drive,spot or l ine drive,

with minimum effortwith minimum effort


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Peripheral and Line FloodsPeripheral and Line Floods

In contrast to using repetitive patterns, aIn contrast to using repetitive patterns, a peripheralperipheral

floodflood utilizes edge wells along reservoir boundaryutilizes edge wells along reservoir boundary

as injectorsas injectors

If a single line of wells along one side, or down theIf a single line of wells along one side, or down the

middle of a field is used, it is called amiddle of a field is used, it is called a line floodline flood

Peripheral Flood


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Selecting a Waterflood PatternSelecting a Waterflood Pattern

Factors Influencing Selection of Waterflood Pattern:Factors Influencing Selection of Waterflood Pattern:

Well spacingWell spacing often dictates selection of waterfloodoften dictates selection of waterfloodpattern. Proper well spacing planning is important:pattern. Proper well spacing planning is important:

-- With regular well spacing, efficient patternWith regular well spacing, efficient patternwaterflooding is possiblewaterflooding is possible

-- Once field is fully developed, pattern optionsOnce field is fully developed, pattern optionsbecome somewhat fixedbecome somewhat fixed

ExistingExisting well patternwell pattern

--

Pick patterns to minimize drilling infil l wellsPick patterns to minimize drilling infil l wells Injection & productionInjection & production objectivesobjectives

-- Choose pattern which provides enough injectorsChoose pattern which provides enough injectors

to provide adequate injection capacity to supportto provide adequate injection capacity to supportanticipated withdrawals from reservoiranticipated withdrawals from reservoir


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Factors Influencing Selection of Waterflood Pattern:Factors Influencing Selection of Waterflood Pattern:

GeologyGeology of reservoirof reservoir

-- Significant heterogeneities such as fractures orSignificant heterogeneities such as fractures orpermeability trends should be major factorspermeability trends should be major factors

-- Prevent adjacent injectors & producers from lyingPrevent adjacent injectors & producers from lying

along a line parallel to direction of maximumalong a line parallel to direction of maximumpermeability or fracture orientationpermeability or fracture orientation

-- Optimum pattern where line connecting adjacentOptimum pattern where line connecting adjacent

injectors is parallel to direction of permeability orinjectors is parallel to direction of permeability orfracture trendfracture trend

If possible, a field should be developed using aIf possible, a field should be developed using a

pattern ultimately suitable for subsequentpattern ultimately suitable for subsequentwaterflooding/EOR operationswaterflooding/EOR operations


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Selecting Wells and SpacingSelecting Wells and Spacing

Irregular Shaped

5-spot Development


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5

9

Base

Calculating sweepCalculating sweep

efficiency using aefficiency using a

reservoir simulatorreservoir simulator

is sometimes theis sometimes themost practicalmost practical

method, especiallymethod, especially

when patterns dowhen patterns donot conform to thenot conform to the

exact geometryexact geometry

used in theused in the

published chartspublished charts

Also practicalAlso practical

when directionalwhen directional

permeability existspermeability exists


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Mobility RatioMobility Ratio

Favorable mobility ratios (M1)

-- Injectivity in the high injection zones increases asInjectivity in the high injection zones increases as

waterflooding occurswaterflooding occurs

-- This causes even earlier water breakthrough &This causes even earlier water breakthrough &

decreases vertical sweep efficiencydecreases vertical sweep efficiency

M bili R i


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Mobility RatioMobility Ratio

For mobility ratios less than 1.0, the relativeFor mobility ratios less than 1.0, the relative

injectivity will decrease as flood front advancesinjectivity will decrease as flood front advances

For mobility ratios greater than 1.0, the relativeFor mobility ratios greater than 1.0, the relative

injectivity will increaseinjectivity will increase

RelativeInjectivity

with

Various

Mobility

Ratios

G i S iG it S ti


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Gravity SegregationGravity Segregation

Effects of gravity segregation:Effects of gravity segregation:

-- Reduces sweep efficiencyReduces sweep efficiency

-- Requires vertical permeabilityRequires vertical permeability

-- Water flows under oilWater flows under oil

-- Rate effect minimalRate effect minimalOil in unswept

reservoir

Injected water

R i H t itiR i H t iti


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Reservoir HeterogeneitiesReservoir Heterogeneities

Understand directional permeabil ity & verticalUnderstand directional permeabil ity & verticalfractures to achieve high sweep efficiencies &fractures to achieve high sweep efficiencies &

successful waterfloodingsuccessful waterflooding

-- If design for directional trends, a very highIf design for directional trends, a very high

sweep efficiency can occursweep efficiency can occur

-- If not, producing wells can water out very rapidly,If not, producing wells can water out very rapidly,

& waterflood can fail& waterflood can fail

Directional permeability trends can be predicted byDirectional permeability trends can be predicted by

regional geological studies, directionally orientedregional geological studies, directionally oriented

cores & analogy to offset fieldscores & analogy to offset fields

Infill drilling is common in helping to improveInfill drilling is common in helping to improve

reservoir recoveryreservoir recovery

R i H t itiR i H t iti


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Reservoir HeterogeneitiesReservoir Heterogeneities

Reservoir heterogeneities which can have impactReservoir heterogeneities which can have impacton waterflood recovery:on waterflood recovery:

-- Pay discontinuities/pinchoutsPay discontinuities/pinchouts-- FaultsFaults

-- Permeability variations/anisotropyPermeabil ity variations/anisotropy

-- Porosity variationsPorosity variations

-- Horizontal fracturesHorizontal fractures

-- Vertical fracturesVertical fractures-- Vertical flow barriers (shales, etc.)Vertical flow barriers (shales, etc.)

-- Formation dipFormation dip


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V ti l S Effi iVertical Sweep Efficiency


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Vertical Sweep EfficiencyVertical Sweep Efficiency

Stratification behavior such as this exists, even inStratification behavior such as this exists, even in

reservoirs with l itt le evidence of verticalreservoirs with l itt le evidence of vertical

stratificationstratification

-- This stratification reduces vertical sweepThis stratification reduces vertical sweep

efficiencyefficiency

-- In many stratified reservoirs, water neverIn many stratified reservoirs, water nevercompletely sweeps the tighter zones beforecompletely sweeps the tighter zones before

abandonment. This results in a reduced value ofabandonment. This results in a reduced value of

EEII because moveable oil is left unrecovered. Thebecause moveable oil is left unrecovered. The

abandonment is caused by an uneconomicalabandonment is caused by an uneconomicaloilcutoilcut

Permeability VariationPermeability Variation


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LayerNumber

Permeabilitymd

Porosity%

Cumulativemd-ft

Cumulativeporosity-ft

1 252.8 15.9 253 16

2 116.0 13.6 369 30

3 83.1 13.8 452 43

4 65.4 13.4 517 57

5 51.8 13.8 569 71

6 43.0 12.6 612 83

7 36.3 11.9 648 95

8 31.5 11.1 680 1069 27.8 12.3 708 118

10 21.2 10.3 729 129

11 18.9 11.1 748 140

12 17.3 11.6 765 151

13 15.8 11.2 781 163

14 14.2 11.0 795 174

15 13.0 11.4 808 185



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The Lorenz coefficient is calculated using theThe Lorenz coefficient is calculated using the

areas designated in the figure below as:areas designated in the figure below as:

ADCAareaABCAarea=tCoefficienLorenz

The value of the LorenzThe value of the Lorenz

coefficient ranges fromcoefficient ranges fromzero to 1. A uniformzero to 1. A uniform

permeability reservoir wil lpermeability reservoir wil l

have a coefficient of 0. Ahave a coefficient of 0. Areservoir with a highreservoir with a high

permeability variation willpermeability variation will

have a coefficient of 0.9 orhave a coefficient of 0.9 orgreatergreater

DykstraDykstra Parsons MethodParsons Method


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DykstraDykstra--Parsons MethodParsons Method

Basic procedure for determining the permeability variation usingBasic procedure for determining the permeabil ity variation usingDykstraDykstra--Parsons method:Parsons method:

1. Divide the permeability samples into layers of equal1. Divide the permeability samples into layers of equal

thickness, usually 1 footthickness, usually 1 foot

2. Arrange the permeability data in decreasing order2. Arrange the permeability data in decreasing order

3. Calculate for each sample the percentage of samples that3. Calculate for each sample the percentage of samples that

have a greater permeability & express this number ashave a greater permeability & express this number as

"percent greater than"percent greater than4. Plot data on log4. Plot data on log--probabil ity paper with permeability on theprobability paper with permeability on the

log scale & "percent greater than" on the probability scalelog scale & "percent greater than" on the probabil ity scale

5. From the best straight line fit of the data, determine the5. From the best straight line fit of the data, determine the

permeability at 84.1 % probabil ity and 50 percent probabil ity.permeability at 84.1 % probabili ty and 50 percent probabil ity.

The best fit straight line should be weighted toward theThe best fit straight line should be weighted toward the

middle pointsmiddle points

6. Compute the permeability variation, V, as:6. Compute the permeabil ity variation, V, as: k

k-k=V

50

84.150

DykstraDykstra Parsons MethodParsons Method


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The value of V is a quantitative indicator of theThe value of V is a quantitative indicator of thedegree of reservoir heterogeneitydegree of reservoir heterogeneity

--A value of zero indicates a homogeneousA value of zero indicates a homogeneous

systemsystem

Dykstra-

Parsons

Probability

Plot

-- IncreasingIncreasing

degrees ofdegrees of

heterogeneityheterogeneitywill havewill have

higher valueshigher values

of Vof V

DykstraDykstra-Parsons MethodParsons Method


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WC = 96.2%WC = 50%

WC = 83.3% WC = 99.0%

Dykstra-Parsons Waterflood Recovery Prediction

ER= (1- 0.40Sw ) = 0.5

ER= (1- 0.72Sw ) =

0.01

ER= (1-Sw ) = 0.01

ER= (1- 0.52Sw ) =

0.01

What Is Production / Injection Control?What Is Production / Injection Control?


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ChemicalChemical SeparationSeparation OtherOther

Gelled Foam

In-Depth GelLignosulfonate High-Temperature Gel

Relative PermeabilityModifiers

Resin

Ringing Gel

Downhole Oil / WaterSeparators

- Conventional

- Reverse coning

Microbial EOR

CompletionsCompletions

Stimulation

Dual StringProduction /Injection

Recompletions

Selective InjectionEquipment

Slimhole

Completions

MechanicalMechanical

Cement

Liners

Mechanical Isolation

Packers

The goal of production / injection control methods isThe goal of production / injection control methods is

to improve reservoir recovery efficiency by:to improve reservoir recovery efficiency by:

-- Opening up unproductive intervalsOpening up unproductive intervals

-- Shutting off swept intervalsShutting off swept intervals



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Primarily impact vertical sweep efficiency, becausePrimarily impact vertical sweep efficiency, because

they can be applied to one or more flow unit layersthey can be applied to one or more flow unit layers

Primarily applicable in the near wellbore area ofPrimarily applicable in the near wellbore area of

specific wellsspecific wells

Several methods may affectSeveral methods may affect arealareal sweep efficiency,sweep efficiency,but are limited because of the significant cost tobut are limited because of the significant cost to

apply them extensively through a large, complexapply them extensively through a large, complex

reservoirreservoir

Several of these methods may apply to eitherSeveral of these methods may apply to either

producers or injectorsproducers or injectors

Production / Injection ControlProduction / Injection Control


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Production / Injection ControlProduction / Injection Control

While remedial actions can usually be performedWhile remedial actions can usually be performed

on either producers or injectors, it is usuallyon either producers or injectors, it is usually

preferable to attack poor conformance at thepreferable to attack poor conformance at the

sourcesource -- the injectorsthe injectors

A good injection profile is the best starting point toA good injection profile is the best starting point to

a successful waterflooda successful waterflood

Before considering remedial options, you mightBefore considering remedial options, you might

want to go back and review the Waterflood Bestwant to go back and review the Waterflood Best

PracticesPractices



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MechanicalMechanical

CementCement

LinersLiners

Mechanical isolationMechanical isolation PackersPackers


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at s oduct o / ject o Co t oj

SeparationSeparation

Downhole oil / water separatorsDownhole oil / water separators

-- ConventionalConventional

-- Reverse coningReverse coning


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Conversions from Producers to InjectorsConversions from Producers to Injectors


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jj

Is it better to convert existing producing wells or toIs it better to convert existing producing wells or to

drill new wells for injection purposes?drill new wells for injection purposes?

-- Sometimes it is necessary to drill replacementSometimes it is necessary to drill replacementwells for injection because the old wells are inwells for injection because the old wells are in

poor mechanical conditionpoor mechanical condition

-- The old wells are then plugged and abandonedThe old wells are then plugged and abandoned

-- However, in this section new wells will refer toHowever, in this section new wells will refer to

new locations that are added to completenew locations that are added to complete

waterfloodwaterflood patterns.patterns.

-- These wells reduce the spacing that existedThese wells reduce the spacing that existed

between the old wellsbetween the old wells


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j

The decision whether to convert existing wells toThe decision whether to convert existing wells toinjection or dril l new injectors should be based uponinjection or dril l new injectors should be based upon

economics, not just a philosophyeconomics, not just a philosophy

The decision should be part of an overallThe decision should be part of an overall waterfloodwaterfloodplan which yields the maximum economic oilplan which yields the maximum economic oil

recoveryrecovery

Other factors should be considered in making aOther factors should be considered in making adecision concerning conversion of existing wellsdecision concerning conversion of existing wells

versus dril ling new wells:versus dril ling new wells:

-- Well bottom hole locationWell bottom hole location-- Casing sizeCasing size

-- Casing conditionCasing condition

-- Completion techniqueCompletion technique



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Well Bottom hole LocationWell Bottom hole Location

The surface location is many times thought toThe surface location is many times thought to

reflect an accurate bottom hole location but due toreflect an accurate bottom hole location but due tonatural drift while drilling and past dril ling practices,natural drift while drilling and past dril ling practices,

the bottom hole location may be some distancethe bottom hole location may be some distance

from the surface locationfrom the surface location

-- May have a bottom hole location out of patternMay have a bottom hole location out of pattern

-- Conversion to injection wil l impact the recovery ofConversion to injection wil l impact the recovery of

that patternthat pattern Thus dril ling a new injection well could place theThus drilling a new injection well could place the

bottom hole location in the center of the patternbottom hole location in the center of the pattern



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Well Bottom hole LocationWell Bottom hole Location

The proper injection pattern should take advantageThe proper injection pattern should take advantage

of the existing well patterns and require a minimumof the existing well patterns and require a minimumnumber of new wellsnumber of new wells

Injection patterns should accommodate knownInjection patterns should accommodate knowngeological features such as natural fracture trendsgeological features such as natural fracture trends

and directional matrix permeabilityand directional matrix permeability

New injection wells may need to be drilled in orderNew injection wells may need to be drilled in orderto take advantage of these geological features, andto take advantage of these geological features, and

to maximize oil recoveryto maximize oil recovery


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Casing SizeCasing Size

Another consideration as to casing size of existingAnother consideration as to casing size of existing

wells, concerns corrosionwells, concerns corrosion

An existing well with small casing may prevent theAn existing well with small casing may prevent the

installation of a liner in the futureinstallation of a liner in the future -- a liner may bea liner may be

necessary if the casing becomes badly corrodednecessary if the casing becomes badly corrodedfrom the injection of corrosive fluidsfrom the injection of corrosive fluids

Drilling new injection wells would permit the properDril ling new injection wells would permit the propersize and weight of casing to be installed, along withsize and weight of casing to be installed, along with

the proper metallurgy for a longerthe proper metallurgy for a longer wellborewellbore lifelife


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Completion TechniqueCompletion Technique

If existing wells were originally completedIf existing wells were originally completed openholeopenhole,,

they may make very good injection wells as far asthey may make very good injection wells as far asrate is concernedrate is concerned

Their injection rate may be greater than comparableTheir injection rate may be greater than comparable

cased injectors due to the open hole's greatercased injectors due to the open hole's greatersurface areasurface area

However, if a poor injection profile occurs, a linerHowever, if a poor injection profile occurs, a liner

may need to be installedmay need to be installed

In large open holes a good cement job can beIn large open holes a good cement job can be

difficult to obtain with a linerdifficult to obtain with a liner


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SlimholeSlimhole CompletionCompletion


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< 5 casingNo tubing

DHOWSDHOWS -- Reverse ConingReverse Coning


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O

W

Selective Injection Equipment (SIE)Selective Injection Equipment (SIE)


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Dual String / CompletionDual String / CompletionInjection or ProductionInjection or Production


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j

Gel TreatmentGel Treatment


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Injection Well with PackerInjection Well with Packer& Tubing& Tubing


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Scab LinerScab Liner


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ImprovingImproving WaterfloodsWaterfloods


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Polymer Flooding:Polymer Flooding:

WaterfloodsWaterfloods can also be improved by polymercan also be improved by polymer

flooding.flooding. Addition of polymer makes the waterAddition of polymer makes the watermore viscous so that oil is produced faster.more viscous so that oil is produced faster.

Obviously, this is not an good idea in a lowObviously, this is not an good idea in a low

permeability reservoir or one with a high claypermeability reservoir or one with a high claycontent that can adsorb the polymer.content that can adsorb the polymer.

ImprovingImproving WaterfloodsWaterfloods


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SurfactantSurfactant--EnhancedEnhanced WaterfloodsWaterfloods::

These projects are only practical in sandstonesThese projects are only practical in sandstones

where adsorption of chemicals is not high or thewhere adsorption of chemicals is not high or thewater is not so hard that the alkali precipitates.water is not so hard that the alkali precipitates.

The projects are very profitable ifThe projects are very profitable if injectivityinjectivity of theof the

chemicals is high and oil recovery is rapid. Thischemicals is high and oil recovery is rapid. Thismeans that projects are likely to be more profitablemeans that projects are likely to be more profitable

if theif the permeabilitypermeabilityDepthDepth/Pattern Area is greater/Pattern Area is greater

than 0.3.than 0.3.

On the other hand, the projects with small wellOn the other hand, the projects with small well

spacing can be shallow, but that larger patternsspacing can be shallow, but that larger patterns

should be deeper and have higher permeability.should be deeper and have higher permeabil ity.

3- waterflooding

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