effect of total concept in well testing for high permeability reservoirs

7/31/2019 Effect of Total Concept in Well Testing for High Permeability Reservoirs

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SPE DISTINGUISHED LECTURER SERIES

is funded principally through a grant of the

SPE FOUNDATION

The Society gratefully acknowledges those companies that support the programby allowing their professionals to participate as Lecturers.

And special thanks to The American Institute of Mining, Metallurgical,

and Petroleum Engineers (AIME) and individual SPE sections for theircontribution to the program.


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APPLICATION OF TOTAL CONCEPT TOAPPLICATION OF TOTAL CONCEPT TO

WELLTESTS IN HIGH PERMEABILITYWELLTESTS IN HIGH PERMEABILITY

RESERVOIRSRESERVOIRS

M. ONYEKONWUM. ONYEKONWU

Petroleum Engineering DepartmentPetroleum Engineering Department

University of PortUniversity of Port--Harcourt, NigeriaHarcourt, Nigeria


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OUTLINEOUTLINE!! BHP Tests and ObjectivesBHP Tests and Objectives

!! Typical Problems in High Permeability FormationTypical Problems in High Permeability Formation

!! What is Total Concept?What is Total Concept?

!! Test and Analysis PrinciplesTest and Analysis Principles

!! Problems and RemediesProblems and Remedies

!! ConclusionsConclusions


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BHP TestBHP Test

!! MeasureMeasure SandSand--face Pressureface Pressurewith Time atwith Time at

SpecifiedSpecified--RateRate ConditionsConditions

Objectives of TestObjectives of Test

!! Determine Reservoir ParametersDetermine Reservoir Parameters!! Determine Well ParametersDetermine Well Parameters

!! Determine Dynamic Influence of OtherDetermine Dynamic Influence of OtherWells/AquiferWells/Aquifer

!! Assess Changes since Previous SurveyAssess Changes since Previous SurveyDatumDatumPressure, Damage Skin, Drainage AreaPressure, Damage Skin, Drainage Area


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Usefulness of TestsUsefulness of Tests

!! Reservoir SurveillanceReservoir Surveillance

!! Determination of Stimulation CandidatesDetermination of Stimulation Candidates

!! Input for Reservoir SimulationInput for Reservoir Simulation

!!Material Balance CalculationMaterial Balance Calculation

!! Gaslift OptimizationGaslift Optimization

T i l P bl i Hi h P bilitT i l P bl i Hi h P bilit


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Typical Problems in High PermeabilityTypical Problems in High PermeabilityReservoirReservoir

!! Possible marred Transient State PhasePossible marred Transient State Phase

Wellbore Storage

Phase

Transient State

Phase

Late Time

Phase

CA B

D E

Increasing Time

Figure 1


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Fast Stabilization

Figure 2

Fast Stabilization

Figure 2

Fast Stabilisation after about 3 mins

3480

3490

3500

3510

3520

3530

3540

3550

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130

Shut - In Time (min)

Shut-In

Pressu

re

(psi)


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Total ConceptTotal Concept

Achieved Objective

BHP Test

FieldO

perator T

est

An

aly

st

ProposalWriter

Figure 4


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Test and Analysis PrincipleTest and Analysis Principle

Test Principle

ReservoirK ?, s ?

Pressure ChangeRate Change

Modelk, s, etc known

(Input) (Output)

Same

Analysis Principle

Pressure ChangeRate Change

(Input) (Output)

Figure 5


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Implications of Test and Analysis PrinciplesImplications of Test and Analysis Principles

"" Rate Changes (Input) are needed to createRate Changes (Input) are needed to create

Pressure Changes (Output)Pressure Changes (Output)

"" Correct rate (input) applied to the reservoirCorrect rate (input) applied to the reservoir mustmust

be knownbe known

"" Unrecorded rate changes will render test uselessUnrecorded rate changes will render test useless

"" Correct pressure changesCorrect pressure changes causedcaused byby raterate

changeschanges must be measuredmust be measured

"" Leak, gauge movement, etc cause pressureLeak, gauge movement, etc cause pressure

changeschanges not associatednot associatedwith rate changeswith rate changes


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Sources of ProblemsSources of Problems

Proposal (Test Programme)Proposal (Test Programme)## Objective/Type of TestObjective/Type of Test

## Test SequencesTest Sequences## Test DurationTest Duration

Procedure

# Depth Control

# Rate Measurement

# Inefficient Shut - In


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Sources of Problems ContinuedSources of Problems Continued

Equipment# Gauges

# Lubricator# Packer

# Gaslift

# Test Separator

Analysis

# Data Quality

# Realistic Model

# Non Reservoir Responses#Application

T d Obj i


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1.1.

Table 1: Tests and Objectives

PermeabilityPermeability

2.2. StorativityStorativity

3.3. Anisotropic PermeabilityAnisotropic Permeability

Values and OrientationValues and Orientation4.4. Sand ContinuitySand Continuity

1.1. Constant RateConstant Rate

Production orProduction or

Injection at theInjection at the

Active WellActive Well

InterferenceInterference

1.1. PermeabilityPermeability

2.2. Skin FactorSkin Factor

3.3. Flow EfficiencyFlow Efficiency

4.4. Average PressureAverage Pressure

5.5. Linear NoLinear NoFlow BoundaryFlow Boundary

1.1. Constant RateConstant RateBuildupBuildup

1.1. PermeabilityPermeability

2.2. Skin FactorSkin Factor

3.3. Drainage VolumeDrainage Volume4.4. Flow EfficiencyFlow Efficiency

5.5. Linear NoLinear NoFlow BoundaryFlow Boundary

1.1. Constant RateConstant Rate

2.2. Long shutLong shut--in Timein Time

DrawdownDrawdown

Information Derived from TestInformation Derived from TestIdeal Conditions of TestIdeal Conditions of TestType of TestType of Test


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Problems on Objective and Types of TestProblems on Objective and Types of Test

!!Obtaining K and S in active WellsObtaining K and S in active Wells

Skin

Perme

ability

P*

P

re

ss

ur

e

TimeFigure 6


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$ Example 1

Table 2: Production Data Prior to Shut-In

67.0067.00

04.3004.30

38.4038.40

2.902.90

18.3018.30

17.5017.50

0.000.000.100.10

0.000.00

0.000.00

0.000.000.000.00

0.00

205.70205.70

210.00210.00

248.40248.40

336.70.336.70.

355.00355.00

372.50372.50

391.70391.70391.80391.80

391.90391.90

391.90391.90

391.90391.90391.90391.90

391.90

12:45:0012:45:00

13:00:0013:00:00

13:15:0013:15:00

14:00:0014:00:00

14:15:0014:15:00

14:30:0014:30:00

15:30:0015:30:0015:45:0015:45:00

16:30:0016:30:00

16:45:0016:45:00

17:00:0017:00:0017:15:0017:15:00

18:15:00

Observed VolumeObserved Volume

(bbl)(bbl)

Meter Reading (bb)Meter Reading (bb)

OilOilTimeTime

FG/SG F D d W llFG/SG F D d W ll


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FG/SG For Dead WellFG/SG For Dead Well

FG/SG F Li W llFG/SG F Li W ll


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FG/SG For Live WellFG/SG For Live Well

Figure 7: Static and Flowing Gradients for a Live WellFigure 7: Static and Flowing Gradients for a Live Well

-2306

-2893-3290-3392-3594-4090-4493

-5793

-5083

-8000

-6000

-4000

-2000

0

0 500 1000 1500 2000 2500

Pressure (psia)

Depth(ft)

Flow ing Gradient

Static Gradient

Valve Location

m = 0.354 psi/ft

m = 0.377 psi/ft

m = 0.01psi/ft

m = average pressure gradient, 0.13 psi/ft

$ Example 2Interference Test with many Active Wells

T D i


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Test DurationTest Duration

Example 1: Normal Well


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Table 3: Effect of Buildup Period on Calculated Results

20902090

37.837.8

0.0250.025

708708

9.099.09

0.02370.0237

Case 2Case 2(Unconstrained(Unconstrained

Skin)Skin)

Case 1Case 1(Constrained(Constrained

Skin)Skin)

18401840

32.432.4

0.02480.0248

Short ShutShort Shut -- InInLong ShutLong Shut -- InIn

Permeability (Permeability (mdmd))

SkinSkin

CCSS (STB/(STB/psipsi))

Calculated ResultsCalculated ResultsParameterParameter

$ Example 2 Horizontal Well


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$ Example 2: Horizontal Well

(LP = 2100ft, k = 1500md, = 0.65cp, = 0.2)Wellbore Storage

Phase

RadialFlow

Late TimePhase

LinearFlow

Pseudo-RadialFlow

Transient State Phase

Increasing Time (hrs.)7.65 11.57.46.0

Figure 11: Flow Geometry and Phases in Well on a Horizontal Well

P d D h C l P bl


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Procedure: Depth Control ProblemsProcedure: Depth Control Problems

!!Good Gauges Imply Accurate PressureGood Gauges Imply Accurate PressureMeasurementMeasurement

!!Wireline Depth Measurement not so AccurateWireline Depth Measurement not so Accurate

!!Depth Error ofDepth Error of 5050 ft Result to an Error of aboutft Result to an Error of about17.517.5 psipsi

!!Some Reservoir not Depleted by as much asSome Reservoir not Depleted by as much as17.5psi per Year17.5psi per Year

!!Depth Error may be Detected from CalculatedDepth Error may be Detected from Calculated

Wellbore Fluid Gradient, FGWellbore Fluid Gradient, FG

(psi/ft)Z

PFG =

Table 4: Depth Control Check


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Table 4: Depth Control Check

0.4390.4395650565058865886--7.07.00.4560.456565756575893589320372037

0.4370.4375601560158345834--8.88.80.3560.356561056105843584320162016

0.4350.43555625562579357930.00.00.4350.435556255625793579319991999

0.3540.35454665466569356930.00.00.4350.435546654665693569319571957

0.3540.3545349534955715571--22.022.00.3830.3835371537155935593191619160.3510.3515246524654635463--30.030.00.3400.340527652765493549318791879

0.3490.3495061506152695269--24.024.00.3160.316508550855293529318141814

0.3440.3444889488950875087--6.06.00.3350.335489548955093509317541754

0.3440.34446134613479447941.01.00.3420.342461246124793479316591659

0.3430.34336893689379837985.05.00.3450.345368436843793379313421342

0.0440.04427392739279327930.00.00.0440.044273927392793279310161016

0.0200.02017701770179317930.00.00.0200.0201770177017931793973973

793793 7717710.00.0771771793793953953


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23Figure 12: Depth Control Check

SG SURVEY : 10543457

857

1257

16572057

2457

2857

32573657

4057

4457

4857

5257

5657

953 1153 1353 1553 1753 1953 2153

Pressure (psia)

Depth(ft)

SG = 0.434(Water)

SG = 0.34(Oil)

SG = 0.04(Gas)

P d R t M t P blProcedure Rate Measurement Problem


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Procedure: Rate Measurement ProblemProcedure: Rate Measurement Problem

Implication

(md)mh

162.6q

=k

Quality Check on Rate Measurement

USLSC )

pt(

24qB

=


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RemediesRemedies

!!There should also be Interest in CorrectThere should also be Interest in CorrectRate MeasurementRate Measurement

!!Flowstation Staff should perform theFlowstation Staff should perform theFlowrate MeasurementFlowrate Measurement

Table 5

Procedure Sampling FrequencyProcedure Sampling Frequency


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Procedure: Sampling FrequencyProcedure: Sampling Frequency

!! High Sampling Frequency as Tests are of Low DurationHigh Sampling Frequency as Tests are of Low Duration

!! Pressure Shift caused by Frequency Change duringPressure Shift caused by Frequency Change during

Critical PeriodCritical Period

Procedure: Bad PracticesProcedure: Bad Practices


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Procedure: Bad PracticesProcedure: Bad Practices

Figure 14: Rocking of Wing Valve

Procedure: Honest ReportingProcedure: Honest Reporting


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Procedure: Honest ReportingProcedure: Honest Reporting


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Gauge Movement ProblemGauge Movement Problem


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Gauge Movement ProblemGauge Movement Problem

Pwf Analysis 1

Pwf Analysis 2

Figure 16: Unnecessary Gauge Movement

EFFECT OF GAUGE MOVEMENTEFFECT OF GAUGE MOVEMENT


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EFFECT OF GAUGE MOVEMENTEFFECT OF GAUGE MOVEMENT

Analysis 1

Analysis 2

Effect of Gauge Movement on ResultsEffect of Gauge Movement on Results


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Effect of Gauge Movement on ResultsEffect of Gauge Movement on Results

950950

-- 5.225.22

1.60451.6045

690690

-- 4.584.58

0.00440.0044

K (K (mdmd))

SS

CCSS (STB/(STB/psipsi))

Analysis 2Analysis 2Analysis 1Analysis 1ParameterParameterTable 6

Equipment: Gaslift Valve


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EquipmentEquipment: Lubricator Leak: Lubricator Leak


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Equipmentq p : Lubricator Leak

Lubricator Leak ContinuedLubricator Leak Continued


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Lubricator Leak ContinuedLubricator Leak Continued

Figure 22: Semilog Plot of Data with Initial Leak from Lubricator

EquipmentEquipment: Packer Problem: Packer Problem


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q p

Communication between Test String and Annulus

Figure 26: Surface Pressure of Test String and Casing(Case with Communication)

AnalysisAnalysis: Data Quality: Data Quality


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AnalysisAnalysis: Data Quality: Data Quality

Data Quality ContinuedData Quality Continued


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40Figure 29: Unrealistic Pressure Difference

AnalysisAnalysis: Unrealistic Model: Unrealistic Model


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AnalysisAnalysis: Unrealistic Model: Unrealistic Model

Figure 30: Misinterpretation of Interference

Unrealistic ModelUnrealistic Model


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Table 7

10001000

2525

0.9 x 100.9 x 10--22

1316.71316.7

34.634.6

0.917 x 100.917 x 10--22

10431043

26.1826.18

1.016 X 101.016 X 10--22

K,K, mdmd

SS

CCS,S, rbrb//psipsi

Type CurveType CurveConventionalConventional

CorrectCorrect

ResultsResults

Calculated ResultsCalculated ResultsParameterParameter

Unrealistic Model ContinuedUnrealistic Model Continued


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Log tLog t

Log PDip due to Phase Segregation

Dip due to Double Porosity

Figure 31: Pressure Derivatives Showing Dips due to Phase Segregationand Double Porosity



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44Figure 32: Effect of Gas Phase Segregation on Pressure Derivative



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45Figure 33: Pressure Difference Plot Showing Gas Segregation Effects

Upward Movement of liquid InterfaceUpward Movement of liquid Interface


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Gauges

Non Reservoir ResponseNon Reservoir Response


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Non Reservoir Response ContinuedNon Reservoir Response Continued


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Liquid Interface Movement

AnalysisAnalysis: Systems Approach: Systems Approach


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Leak

No Straight Line

Figure 37(a) &(b): Semilog Plots of Tests in adjacent WellsDraining the same Reservoir

Leak

Straight Line

Application of ResultsApplication of Results


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PsdPwf

rw ro

Psc

Psp

PT

P UsefulDrawdown

kh141.2qB

p-

p

d

wf

sd

sp

p

R

sd

=

=

Indices for Selecting Stimulation Candidates

0.470.470.950.95--0.910.910.750.750.710.710.340.34RR

190190115115--17.517.5677677204204135.2135.230.7230.72PsdPsd,, psipsi

3.153.156666--17.617.6454516.616.69.19.13.343.34DamageDamage

SkinSkin

3673671191199.99.9723723216.6216.6174.2174.257.8657.86PPTT,, psipsi63.663.61961966.16.119219226.426.43.53.518.418.4Total SkinTotal Skin

77665544332211

WELL TEST NUMBERWELL TEST NUMBER

ExampleExample


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Table 8: Result s of Pre-St imulat ion and Post -St imulat ion Test (Well A)

3.083.082.372.37Oil PIOil PI

0.1910.1910.3670.367R =R = ppdamageskindamageskin/Drawdown/Drawdown

32.332.325.0225.02ppdamageskindamageskin ((psipsi))

1.31.37.577.57Damage SkinDamage Skin

2.22.22.22.2Mechanical SkinMechanical Skin

59.759.732.4532.45p due to Total Skin (p due to Total Skin (psipsi))

4.854.859.829.82Total Skin (s)Total Skin (s)

168.72168.7268.1668.16Drawdown (Drawdown (psipsi))

570570568568Rate (STB/day)Rate (STB/day)

ExampleExample


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Table 9: Result s of Pre-St imulat ion and Post -St imulat ion Test (Well B)

2.142.140.150.15Oil PIOil PI

0.480.480.710.71R =R = ppdamageskindamageskin/Drawdown/Drawdown

102.2102.2259.53259.53ppdamageskindamageskin ((psipsi))

212.18212.18365.63365.63DrawdownDrawdown,, psipsi

8.48.446.5746.57Damage SkinDamage Skin0.20.20.20.2Mechanical SkinMechanical Skin

8.588.5846.7446.74Total Skin (s)Total Skin (s)

5395396666Rate (STB/day)Rate (STB/day)

Good Test Possible if:Good Test Possible if:


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!!Good proposal that meets objectiveGood proposal that meets objective

!!Calibrated gauges and equipment in goodCalibrated gauges and equipment in goodworking conditionsworking conditions

!!Good test procedureGood test procedure Rate MeasurementRate Measurement

Depth ControlDepth Control

Truthful ReportingTruthful Reporting

!!Analysis based on knowledgeAnalysis based on knowledge

Savings from Applying Total ConceptSavings from Applying Total Concept


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5416.816.8TotalTotal

4.04.010% Well10% Well CampainCampain))

3.03.0Horizontal Well changed toHorizontal Well changed to RecompletionRecompletion

Sand D5.0X DevelopmentSand D5.0X Development

1.01.0WellWell--11 (Sidetrack raise Trajectory)11 (Sidetrack raise Trajectory)

3.03.0Dump Creek (10% of the 6 fewer Wells required)Dump Creek (10% of the 6 fewer Wells required)

3.03.0SandSand--X Block (New Well Cancelled)X Block (New Well Cancelled)

1.01.0Sand F4.0/F4.1X Production (3Sand F4.0/F4.1X Production (3 MbopdMbopd))

Reservoir SurveillanceReservoir Surveillance

1.01.0Gaslift OptimizationGaslift Optimization (10% improvement of Target at(10% improvement of Target at$1/bbl)$1/bbl)

0.80.8StimulationStimulation (about 5 Jobs contribute to finding 5 more)(about 5 Jobs contribute to finding 5 more)

Well SurveillanceWell Surveillance

Table 10: Benefi t s f rom BHP Survey

ConclusionsConclusions


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!!BHP Analysis NOT an Isolated EventBHP Analysis NOT an Isolated Event

!!The BHP Proposal and Field PracticesThe BHP Proposal and Field Practices

Influence ResultsInfluence Results

!!Problem Sources IncludeProblem Sources Include

##Unrecorded Rate ChangesUnrecorded Rate Changes

##Leak/InterferenceLeak/Interference

##GaugesGauges

##Improper ProcedureImproper Procedure

##Improper Analysis/UsageImproper Analysis/Usage##NonNon--UniquenessUniqueness

Conclusions ContinuedConclusions Continued


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!!Need for Enlightenment and Supervision ofNeed for Enlightenment and Supervision ofTestsTests

!!Need to ascertain what causes theNeed to ascertain what causes thePressure change before the AnalysisPressure change before the Analysis

!!Total Concept is Useful and can generallyTotal Concept is Useful and can generally

be applied in all Reservoirsbe applied in all Reservoirs


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THANK YOUTHANK YOU

effect of total concept in well testing for high permeability reservoirs

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