optimization of perforated completions for horizontal wells in...

ByBy

MAHDI BOURENANEMAHDI BOURENANE

JANUARY 2003JANUARY 2003

Optimization of Perforated Completions for Horizontal Optimization of Perforated Completions for Horizontal

Wells in HighWells in High--Permeability, Thin Oil ZonePermeability, Thin Oil ZoneHassiHassi RR’’melmel Oil Rim, AlgeriaOil Rim, Algeria

SONATRACHSONATRACH

DIVISION PRODUCTIONDIVISION PRODUCTION

HASSI RHASSI R’’MELMEL

OUTLINEOUTLINE

IntroductionIntroduction

Objectives of Objectives of thethe StudyStudy

Statement of the problemStatement of the problem

GeologicalGeological andand ReservoirReservoir CharacterizationCharacterization

SensitivitySensitivity AnalysisAnalysis on on PerforatedPerforated CompletionsCompletions

Performance of Performance of InvertedInverted HighHigh Angle Angle CompletionCompletionCase Case StudyStudy : HRZ: HRZ--0909

Conclusions Conclusions andand RecommendationsRecommendations

MethodologyMethodology

The success of Horizontal well technology is mainly due to the aThe success of Horizontal well technology is mainly due to the advantages that dvantages that

horizontal wells offer such as : productivity improvement, coninhorizontal wells offer such as : productivity improvement, coning reduction and g reduction and

sand problems attenuation. sand problems attenuation.

Very often, either for geological reasons or for production purVery often, either for geological reasons or for production purposes, the wells poses, the wells

need to be cased and perforated. It is important in this case toneed to be cased and perforated. It is important in this case to know how much know how much

of the horizontal length should be perforated and where to locatof the horizontal length should be perforated and where to locate the e the

perforations.perforations.

In this respect, minimizing the horizontal section to be perforIn this respect, minimizing the horizontal section to be perforated for an ated for an

optimization purpose is justified.optimization purpose is justified.

INTRODUCTIONINTRODUCTIONINTRODUCTION

INTRODUCTION(Continued)

INTRODUCTIONINTRODUCTION((ContinuedContinued))

A considerable number of studies have been done on how to A considerable number of studies have been done on how to

optimize the perforated completions for horizontal wells; but veoptimize the perforated completions for horizontal wells; but very ry

few of them took into consideration the reservoir heterogeneity few of them took into consideration the reservoir heterogeneity as as

well as coning problems.well as coning problems.

Probably one the most important work directly related to this Probably one the most important work directly related to this

topic is the one developed by Goods and Wilkinson. They have topic is the one developed by Goods and Wilkinson. They have

presented an analytical solution for the performance of partiallpresented an analytical solution for the performance of partially y

completed horizontal well.completed horizontal well.



According to their model, the inflow performance of a well is According to their model, the inflow performance of a well is

related to the longrelated to the long--time behavior of constant rate pressure.time behavior of constant rate pressure.

So, they derived a formula that expresses the inflow performancSo, they derived a formula that expresses the inflow performance e

of a partially open horizontal well as follows :of a partially open horizontal well as follows :

Where :Where :

PPIDID : Dimensionless Inflow Pressure.: Dimensionless Inflow Pressure.

S*S*mm : Skin Factor.: Skin Factor.

)(1008.7

*

3

mIDoo

hh SP

hkJ +×=

−

βµ ( STB/D ( STB/D –– PSI )PSI )



Goods and WilkinsonGoods and Wilkinson’’s model limitations :s model limitations :

It considers the reservoir as Homogeneous.It considers the reservoir as Homogeneous.

It does not consider the gas and water coning effects.It does not consider the gas and water coning effects.

So in this study, a numerical solution was developed to optimizeSo in this study, a numerical solution was developed to optimize

the perforated completions in a heterogeneous reservoir laying the perforated completions in a heterogeneous reservoir laying

between a large gas cup and active aquifer (Double coning between a large gas cup and active aquifer (Double coning

problem).problem).

In thin oil zones with high permeability, horizontal wells are uIn thin oil zones with high permeability, horizontal wells are used to minimize water sed to minimize water

and or gas coning; so that, an inappropriate perforated completiand or gas coning; so that, an inappropriate perforated completion scheme may on scheme may

actually exacerbate the problem at the downstream end of the welactually exacerbate the problem at the downstream end of the well.l.

In addition, the productivity of horizontal wells producing froIn addition, the productivity of horizontal wells producing from such reservoir may m such reservoir may

be severely restricted by frictional pressure losses within the be severely restricted by frictional pressure losses within the perforation section of perforation section of

the well. the well.

Hence, in thin oil zones, optimizing the perforated completioHence, in thin oil zones, optimizing the perforated completion in horizontal wells n in horizontal wells

will substantially improve the oil recovery, alleviate gas and wwill substantially improve the oil recovery, alleviate gas and water coning, and so ater coning, and so

that minimize the investment cost.that minimize the investment cost.

STATEMENT OF THE PROBLEMSTATEMENT OF THE PROBLEMSTATEMENT OF THE PROBLEM

OBJECTIVES OF THE STUDYOBJECTIVES OF THE STUDYOBJECTIVES OF THE STUDY

Investigate the effect of the most relevant reservoir parametersInvestigate the effect of the most relevant reservoir parameters on on

horizontal well performance for different perforation alternativhorizontal well performance for different perforation alternatives.es.

Find out the optimum perforation scheme for horizontal wells in Find out the optimum perforation scheme for horizontal wells in HassiHassi

RR’’melmel Oil Rim.Oil Rim.

Study the performance of the Inverted High Angle completion in Study the performance of the Inverted High Angle completion in HassiHassi

RR’’melmel Oil Rim (Case study : HRZOil Rim (Case study : HRZ--09).09).

Generate correlation curves that can be used to optimize the Generate correlation curves that can be used to optimize the

perforated completions for Horizontal wells.perforated completions for Horizontal wells.

METHODOLOGYMETHODOLOGYMETHODOLOGY

Reservoir Characterization of the AReservoir Characterization of the A--Sand reservoir of Sand reservoir of HassiHassi RR’’melmel

Oil Rim using the sedimentary subdivision and the best approacheOil Rim using the sedimentary subdivision and the best approaches s

to estimate the to estimate the petrophysicalpetrophysical properties. Hence, the most accurate properties. Hence, the most accurate

geological model to be introduced in the simulator.geological model to be introduced in the simulator.

A single well simulation model was built to investigate the effA single well simulation model was built to investigate the effect of ect of

perforation length and its distribution, reservoir permeability,perforation length and its distribution, reservoir permeability,

vertical anisotropy and vertical anisotropy and arealareal anisotropy on horizontal well anisotropy on horizontal well

performance. performance.

METHODOLOGY(Continued)

METHODOLOGYMETHODOLOGY(Continued)(Continued)

A second single well model was involved in a real case where thA second single well model was involved in a real case where the e

performance of the well HRZ09, for different perforation schemesperformance of the well HRZ09, for different perforation schemes, ,

was a concern. To cover this part, three points have to be was a concern. To cover this part, three points have to be

developed :developed :

HistoryHistory matchingmatching

Comparative Comparative studystudy basedbased on on wellwell performanceperformance

Comparative Comparative studystudy basedbased on on EconomicEconomic AnalysisAnalysis

RESERVOIR CHARACTERIZATION

RESERVOIR RESERVOIR CHARACTERIZATION CHARACTERIZATION









PETROPHYSICAL (RESERVOIR) CHARACTERIZATION

PETROPHYSICAL (RESERVOIR) PETROPHYSICAL (RESERVOIR) CHARACTERIZATIONCHARACTERIZATION

Cases where core and log analysis data were available, the priorCases where core and log analysis data were available, the priority for ity for

porosity and permeability determination was given to core analysporosity and permeability determination was given to core analysis.is.

The permeability for the nonThe permeability for the non--cored sections were estimated from the cored sections were estimated from the

curve fitting of the permeabilitycurve fitting of the permeability--porosity relationship.porosity relationship.

Effective Formation :Effective Formation :

CutCut--off porosity = 4%off porosity = 4%

CutCut--off Shale content = 35%off Shale content = 35%

CutCut--off Water Saturation = 55%off Water Saturation = 55%

CutCut--off Permeability = 1md off Permeability = 1md RESERVOIR CHARACTERIZATION RESERVOIR CHARACTERIZATION



( )12 2 −= ShIShSh IV

( )

++−=

5.02 4

2 tW

m

Sh

Sh

Sh

ShmWW RaRR

VRVaRS

φφ

22707.0 DcNC φφφ += φe = φ(1-Vsh)

Shale Content, Shale Content, VshVsh ::

Effective Effective PorosityPorosity ::

WaterWater Saturation :Saturation :

( ( OlderOlder Rock )Rock )

( ( VshVsh>10% )>10% )

RESERVOIR CHARACTERIZATION RESERVOIR CHARACTERIZATION



Porosity-Permeability Correlation

LnK = 0.401(Ph) -2.594R2 = 0.7739

0.01

0.1

1

10

100

1000

10000

0 5 10 15 20 25 30Porosity, %

Perm

eabi

lity,

md

LnK = 0.401(Ph) -2.594R2 = 0.7739

0.01

0.1

1

10

100

1000

10000

0 5 10 15 20 25 30Porosity, %

Perm

eabi

lity,

md

Lnk = 0.401(Ph) - 2.594

R2 = 0.7739

Lnk = 0.401(Ph) - 2.594

R2 = 0.7739


RESERVOIR SUBDIVISIONRESERVOIR SUBDIVISIONRESERVOIR SUBDIVISION

L1L2

Top ATop A

BottomBottom AA

L3M1M2M3U1U2U3

HR-189

HRZ-09

HR-198 HR-210

HRE-201

HRE-402

HR-208HRE-202

HRE-203


Layer 14 Layer 14 Layer 13 Layer 13 Layer 12 Layer 12 Layer 11 Layer 11 Layer 10 Layer 10 Layer 9 Layer 9 Layer 8 Layer 8 Layer 7 Layer 7 Layer 6 Layer 6 Layer 5 Layer 5 Layer 4 Layer 4 Layer 3 Layer 3

HR-189

HRZ-09

HR-198 HR-210

HRE-201

HRE-402

HR-208HRE-202

HRE-203

Layer 2 Layer 2 Layer 1 Layer 1


HR-189

HRZ-09

HR-198 HR-210

HRE-201

HRE-402

HR-208HRE-202

HRE-203

Top ATop A

BottomBottom AA

GEOLOGICAL MODEL REFINEMENT

GEOLOGICAL MODEL GEOLOGICAL MODEL REFINEMENTREFINEMENT

HRHR--189189GeologicalGeological

layerlayerLayerLayer

NN°°Gross thickness Gross thickness

(m)(m)Net thickness Net thickness

(m)(m)PorosityPorosity(fraction)(fraction)

Water SaturationWater Saturation(%)(%)

PermeabilityPermeability((mdmd))

U3U3 11 5.55.5 2.752.75 0.07700.0770 45.1445.14 1.761.76U2U2 22 44 1.251.25 0.10130.1013 24.5224.52 33.5633.56U1U1 33 2.52.5 2.52.5 0.22900.2290 11.6111.61 337.99337.99

44 1.251.25 1.251.25 0.22900.2290 11.6111.61 337.99337.99M3M3 55 2.52.5 2.52.5 0.26410.2641 21.4721.47 493.90493.90

66 2.52.5 22 0.26410.2641 21.4721.47 493.90493.9077 2.52.5 1.251.25 0.25660.2566 17.9217.92 423.75423.7588 2.52.5 2.52.5 0.25660.2566 17.9217.92 423.75423.7599 2.752.75 2.52.5 0.25660.2566 17.9217.92 423.75423.75

M1M1 1010 1.51.5 11 0.23640.2364 27.7627.76 602.54602.541111 1.251.25 11 0.23640.2364 27.7627.76 602.24602.24

L3L3 1212 3.753.75 2.252.25 0.24160.2416 28.9228.92 257.94257.94L2L2 1313 1.751.75 00 0000 0000 0000L1L1 1414 2.752.75 00 0000 0000 0000

M2M2


RESULTS OF THE PETROPHYSICAL

CHARACTERIZATION

RESULTS OF THE PETROPHYSICAL RESULTS OF THE PETROPHYSICAL

CHARACTERIZATIONCHARACTERIZATION

SENSITIVITY ANALYSIS

ON PERFORATED COMPLETIONS

SENSITIVITY ANALYSIS SENSITIVITY ANALYSIS

ON PERFORATED COMPLETIONSON PERFORATED COMPLETIONS









SENSITIVITY ANALYSIS

ON PERFORATED COMPLETIONS

SENSITIVITY ANALYSIS SENSITIVITY ANALYSIS

ON PERFORATED COMPLETIONSON PERFORATED COMPLETIONS

A parametric study is conducted to analyze the effect of thA parametric study is conducted to analyze the effect of the most e most

relevant reservoir parameters on horizontal well performance forrelevant reservoir parameters on horizontal well performance for

different Perforation Schemes. This in Highdifferent Perforation Schemes. This in High--permeability thin Oil permeability thin Oil

zone.Thesezone.These parameters are :parameters are :

•• Perforation Perforation lengthlength andand itsits DistributionDistribution

•• ReservoirReservoir PermeabilityPermeability

•• Vertical Vertical anisotropyanisotropy RatioRatio

•• HoriziontalHoriziontal anisotropyanisotropy RatioRatio

RESERVOIR GEOMETRY FOR HORIZONTAL WELL MODEL

RESERVOIR GEOMETRY FOR RESERVOIR GEOMETRY FOR

HORIZONTAL WELL MODELHORIZONTAL WELL MODEL

To perform this study, a singleTo perform this study, a single--horizontal well model is needed. horizontal well model is needed.

For this simulation model, a 3For this simulation model, a 3--D regular Cartesian grid was built.D regular Cartesian grid was built.

•• NumberNumber of blocks in Xof blocks in X--directiondirection 1515

•• NumberNumber of blocks in Yof blocks in Y--directiondirection 1515

•• NumberNumber of blocks in Zof blocks in Z--directiondirection 1414

•• Total Total numbernumber of blocksof blocks 15x15x14=315015x15x14=3150SENSITIVITY ANALYSISSENSITIVITY ANALYSIS

Once the single well simulation model was built, the sensitiOnce the single well simulation model was built, the sensitivity vity

analysis can be performed for different perforation alternativesanalysis can be performed for different perforation alternatives. All . All

the simulation runs were done for 12 years forecast.the simulation runs were done for 12 years forecast.

Assuming that the well is completed with a fully cemented anAssuming that the well is completed with a fully cemented and d

perforated liner, and the horizontal perforated liner, and the horizontal wellborewellbore has 500m long, seven has 500m long, seven

(07) perforation schemes were proposed for this study. These are(07) perforation schemes were proposed for this study. These are ::

SENSITIVITY ANALYSISSENSITIVITY ANALYSIS

The Proposed Perforation schemes

The Proposed Perforation The Proposed Perforation schemesschemes

L = 500mL = 500m

LpLp = 500m= 500m

Case 1 : Case 1 : LpLp = 500m (100%)= 500m (100%)

ToeToeHeelHeel






Case 2 : Case 2 : LpLp = 400m (80%)= 400m (80%)

LpLp = 400m= 400m

HeelHeel ToeToe

L = 500mL = 500m




Case 3 : Case 3 : LpLp = 300m (60%)= 300m (60%)

LpLp = 300m= 300m

HeelHeel ToeToe

L = 500mL = 500m




Case 4 : Case 4 : LpLp = 200m (40%)= 200m (40%)

LpLp = 200m= 200m

HeelHeel ToeToe

L = 500mL = 500m




Case 5 : Case 5 : LpLp = 100m (20%)= 100m (20%)

LpLp = 100m= 100m

HeelHeel ToeToe

L = 500mL = 500m




Case 6 : Case 6 : LpLp = 300m UD (60%)= 300m UD (60%)

LpLp = 100m= 100m LpLp = 100m= 100m LpLp = 100m= 100m

HeelHeel ToeToe

L = 500mL = 500m




Case 7 : Case 7 : LpLp = 200m TE (40%)= 200m TE (40%)

LpLp = 200m= 200m

L = 500mL = 500m

ToeToeHeelHeel


1.1. Base Case ( Perforation Base Case ( Perforation LengthLength andand Distribution Distribution EffectEffect) :) :

All the reservoir parameters are kept unchanged; and they tAll the reservoir parameters are kept unchanged; and they took ook

values that match those of values that match those of HassiHassi RR’’melmel Oil rim. These are :Oil rim. These are :

KK = 500md= 500md

KvKv//KhKh = 0.01= 0.01

KyKy//KxKx = 1= 1

QoQo = 100 SM= 100 SM33/D/D


Base CasePerforation Length and its Distribution Effect

Base CaseBase CasePerforation Length and its Distribution EffectPerforation Length and its Distribution Effect


Plot of Oil Recovery Versus Time For different perforation scenarios

0

2

4

6

8

10

12

14

0 2 4 6 8 10 12 14Time, Year

Oil

Rec

over

y, %

Lp=100%

Lp=80%

Lp=60%

Lp=40%

Lp=20%

Lp=60% UD

Lp=40% TE




Plot of Gas-Oil Ratio Versus Time For different perforation scenarios

0

2000

4000

6000

8000

10000

12000

0 2 4 6 8 10 12 14Time, Year

GO

R, N

M3/

SM3

Lp=100%

Lp=80%

Lp=60%

Lp=40%

Lp=20%

Lp=60% UD

Lp=40% TE



Perforation Distribution Perforation Distribution EffectEffect


Plot of Gas-Oil Ratio versus time for the comparisonbetween case 3 and case 6

0100020003000400050006000700080009000

0 2 4 6 8 10 12 14Time, Year

GO

R, N

M3/

SM3

Lp=60% CP

Lp=60% UD

Plot of Oil Recovery versus time for the comparisonbetween case 3 and case 6

0

2

4

6

8

10

12

14

0 2 4 6 8 10 12 14Time, Year

Oil

Rec

over

y, %

Lp=60% CP

Lp=60% UD



Perforation Distribution Perforation Distribution EffectEffect


Plot of Oil Recovery versus Time for the comparisonbetween case 4 and case 7

0

2

4

6

8

10

12

0 2 4 6 8 10 12 14Time, Year

Oil

Rec

over

y,%

Lp=40% HE

Lp=40% TE

Plot of Gas-Oil Ratio versus Time for the comparisonbetween case 4 and case 7

0

1000

2000

3000

4000

5000

6000

7000

8000

0 2 4 6 8 10 12 14Time, Year

GO

R, N

M3/

SM3

Lp=40% HE

Lp=40% TE




0

2

4

6

8

10

12

14

Oil

Rec

over

y, %

Lp=100% LP=80%CP LP=60%CP LP=40%HE LP=20%CP LP=60%UD LP=40%TE

Perforation Schemes

Oil Recovery for the different perforation schemes proposedafter 12 years production

- Base Case -

Best CaseBest CaseBest Case



0

2000

4000

6000

8000

10000

12000

Gas

-Oil

Rat

io, N

M3/

SM3

Lp=100% LP=80%CP LP=60%CP LP=40%HE LP=20%CP LP=60%UD LP=40%TE

Perforation Schemes

Gas-Oil Ratio for the different perforation schemes proposedafter 12 years production

- Base Case -

Best CaseBest CaseBest Case




In case of continuous perforation, The higher the perforation leIn case of continuous perforation, The higher the perforation length, the ngth, the

higher the oil recovery, and the higher the Gashigher the oil recovery, and the higher the Gas--Oil ratio.Oil ratio.

The perforation length can be reduced, and in many cases, withoThe perforation length can be reduced, and in many cases, without a ut a

substantial decrease in oil recovery. Moreover, lower values of substantial decrease in oil recovery. Moreover, lower values of

perforation length lead to lower gasperforation length lead to lower gas--oil ratios produced.oil ratios produced.

Hence, the perforation length has to be optimized with respectHence, the perforation length has to be optimized with respect not only to not only to

oil recovery, but also to gasoil recovery, but also to gas--oil ratio in order to guarantee the lowest oil ratio in order to guarantee the lowest

investment cost in gas facilities.investment cost in gas facilities.




The reservoir produces more efficiently when the perforation inThe reservoir produces more efficiently when the perforation intervals are tervals are

uniformly distributed along theuniformly distributed along the wellborewellbore rather than being continuously rather than being continuously

placed. placed.

Case 6 (60% Uniformly Distributed Perforation) is the most favorCase 6 (60% Uniformly Distributed Perforation) is the most favorable case able case

of all the proposed perforation schemes since it guaranties: of all the proposed perforation schemes since it guaranties:

•• High Oil recovery and low GasHigh Oil recovery and low Gas--oil ratio.oil ratio.

•• Pressure and production rate stabilization.Pressure and production rate stabilization.

•• Coning reduction.Coning reduction.

•• Lowest investment cost (Maximum net Present Value).Lowest investment cost (Maximum net Present Value).SENSITIVITY ANALYSISSENSITIVITY ANALYSIS



RESERVOIR PERMEABILITY EFFECT

RESERVOIR PERMEABILITY RESERVOIR PERMEABILITY EFFECTEFFECT


To investigate the effect of reservoir permeability on horizTo investigate the effect of reservoir permeability on horizontal well ontal well

performance for various completion alternatives, we considered fperformance for various completion alternatives, we considered five ive

values of reservoir permeability : values of reservoir permeability :

2.2. Reservoir Permeability EffectReservoir Permeability Effect

KK11 = 1000 = 1000 mdmd

KK22 = 500 = 500 mdmd

KK33 = 100 = 100 mdmd

KK44 = 50 = 50 mdmd

KK55 = 10 = 10 mdmd



KK11 = 1000 = 1000 mdmd


0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 2 4 6 8 10 12 14Time, Year

GO

R, N

M3/

SM3

Lp=100%

Lp=80%

Lp=60%

Lp=40%

Lp=20%

Lp=60% UD

Lp=40% TE


0

2

4

6

8

10

12

14

16

0 2 4 6 8 10 12 14Time, Year

Oil

Rec

over

y,%

Lp=100%

Lp=80%

Lp=60%

Lp=40%

Lp=20%

Lp=60% UD

Lp=40% TE

Horizontal well performance for the different perforation schemeHorizontal well performance for the different perforation schemessSENSITIVITY ANALYSISSENSITIVITY ANALYSIS



Reservoir Permeability values

0

2

4

6

8

10

12

14

16

0 20 40 60 80 100Perforation length,%

Oil

Rec

over

y, %

K1=1000md K2=500md K3=100mdK4=50md K5=10md

0

5000

10000

15000

20000

25000

30000

35000

0 20 40 60 80 100Perforation Length,%

GO

R,N

M3/

SM3

K1=1000md K2=500md K3=100mdK4=50md K5=10md

Effect of Perforation Length on well performance for differenEffect of Perforation Length on well performance for different t RReservoir Permeabilityeservoir Permeability values after 12 years values after 12 years




2

4

6

8

10

12

14

16

10 100 1000Permeabilty, md

Oil

Rec

over

y, %

Lp=100% Lp=80% Lp=60%Lp=40% Lp=20% Lp=60% UDLp=40% TE

2000

7000

12000

17000

22000

27000

32000

10 100 1000Permeabilty, md

GO

R, N

M3/

SM3


Effect of Effect of Reservoir PermeabilityReservoir Permeability on well performance for on well performance for different perforation scenarios after 12 yearsdifferent perforation scenarios after 12 years




The higher the reservoir permeability, the higher the oil recoThe higher the reservoir permeability, the higher the oil recovery very

for any perforated completion alternative.for any perforated completion alternative.

In case of a thin oil rim sandwiched between a large gasIn case of a thin oil rim sandwiched between a large gas--cap and cap and

an active aquifer, lower values of reservoir permeability yield an active aquifer, lower values of reservoir permeability yield

higher gashigher gas--oil ratio in comparison to the case of higher oil ratio in comparison to the case of higher

permeability values. permeability values.

Hence, high reservoir permeability values (K>50md) are more Hence, high reservoir permeability values (K>50md) are more

favorable in such case ( thin oil rim).favorable in such case ( thin oil rim).SENSITIVITY ANALYSISSENSITIVITY ANALYSIS

VERTICAL ANISOTROPY EFFECT

VERTICAL ANISOTROPY VERTICAL ANISOTROPY EFFECTEFFECT


3.3. Vertical Anisotropy EffectVertical Anisotropy Effect

Four (04) vertical anisotropy ratios were examined : Four (04) vertical anisotropy ratios were examined :

((KvKv//KhKh))11 = 1= 1

((KvKv//KhKh))22 = 0.1= 0.1

((KvKv//KhKh))33 = 0.01= 0.01

((KvKv//KhKh))44 = 0.001= 0.001


((KvKv//KhKh))11 = 1= 1


0

1

2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14Time, Year

Oil

Rec

over

y,%

Lp=100%Lp=80%Lp=60%Lp=40%Lp=20%Lp=60% UDLp=40% TE


0

2000

4000

6000

8000

10000

12000

14000

0 2 4 6 8 10 12 14Time, Year

GO

R, N

M3/

SM3

Lp=100%

Lp=80%

Lp=60%

Lp=40%

Lp=20%

Lp=60% UD

Lp=40% TE



Effect of Perforation Length on well performance for differenEffect of Perforation Length on well performance for different t Vertical Anisotropy valuesVertical Anisotropy values after 12 years after 12 years




02468

101214161820

0 20 40 60 80 100 120Perforation length, %

Oil

Rec

over

y, %

(Kv/Kh)1=1 (Kv/Kh)2=0.1

(Kv/Kh)3=0.01 (Kv/Kh)4=0.001

02000400060008000

100001200014000160001800020000

0 20 40 60 80 100 120Perforation length,%

GO

R, N

M3/

SM3

(Kv/Kh)1=1 (Kv/Kh)2=0.1

(Kv/Kh)3=0.01 (Kv/Kh)4=0.001


Effect of Effect of Vertical AnisotropyVertical Anisotropy on well performance for different on well performance for different perforation scenarios after 12 yearsperforation scenarios after 12 years



02468

101214161820

0.001 0.01 0.1 1Kv/Kh

Oil

Rec

over

y,%


c

02000400060008000

100001200014000160001800020000

0.001 0.01 0.1 1Kv/Kh

GO

R, N

M3/

SM3



In case of a thin oil rim trapped between a large gasIn case of a thin oil rim trapped between a large gas--cap and an cap and an

active aquifer, the higher the vertical anisotropy ratio, the loactive aquifer, the higher the vertical anisotropy ratio, the lower wer

the oil recovery for any perforation scenario. the oil recovery for any perforation scenario.

Hence, in this case, low anisotropy ratios are preferable notHence, in this case, low anisotropy ratios are preferable not only only

to get higher oil recovery but also to come out with the least to get higher oil recovery but also to come out with the least

amount of gas produced.amount of gas produced.



HORIZONTAL ANISOTROPY EFFECT

HORIZONTAL ANISOTROPY HORIZONTAL ANISOTROPY EFFECTEFFECT


4.4. Horizontal Anisotropy EffectHorizontal Anisotropy Effect

Four (04) values of horizontal anisotropy were considered tFour (04) values of horizontal anisotropy were considered to o

investigate its effect on horizontal well performance for differinvestigate its effect on horizontal well performance for different ent

perforation alternatives. These are :perforation alternatives. These are :

((KyKy//KxKx))11 = 10= 10

((KyKy//KxKx))22 = 5= 5

((KyKy//KxKx))33 = 1= 1

((KyKy//KxKx))44 = 0.1= 0.1



((KyKy//KxKx))11 = 10= 10


0

2

4

6

8

10

12

14

16

0 2 4 6 8 10 12 14Time, Year

Oil

Rec

over

y, %

Lp=100%

Lp=80%

Lp=60%

Lp=40%

Lp=20%

Lp=60% UD

Lp=40% TE


0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0 2 4 6 8 10 12 14Time, Year

GO

R,N

M3/

SM3

Lp=100%

Lp=80%

Lp=60%

Lp=40%

Lp=20%

Lp=60% UD

Lp=40% TE




0

2000

4000

6000

8000

10000

12000

14000


GO

R, N

M3/

SM3

(Ky/Kx)1=10 (Ky/Kx)2=5(Ky/Kx)3=1 (Ky/Kx)4=0.1

02468

10121416


Oil

Rec

over

y,%

(Ky/Kx)1=10 (Ky/Kx)2=5(Ky/Kx)3=1 (Ky/Kx)4=0.1

Effect of Perforation Length on well performance for differenEffect of Perforation Length on well performance for different t Horizontal Anisotropy valuesHorizontal Anisotropy values after 12 years after 12 years




4

6

8

10

12

14

0.1 1 10Ky/Kx

Oil

Rec

over

y, %


400050006000700080009000

100001100012000130001400015000

0.1 1 10Ky/Kx

GO

R, N

M3/

SM3


Effect of Effect of Horizontal AnisotropyHorizontal Anisotropy on well performance for on well performance for different perforation scenarios after 12 yearsdifferent perforation scenarios after 12 years




For all the perforated completion schemes, the higher For all the perforated completion schemes, the higher

the horizontal anisotropy the horizontal anisotropy ((KyKy//KxKx),), the higher the oil the higher the oil

recovery. recovery.

This is because the well is drilled in XThis is because the well is drilled in X--direction. However, if direction. However, if

the well was drilled in Ythe well was drilled in Y--direction, the opposite trend would direction, the opposite trend would

be got.be got.


Conclusion of

The Sensitivity Analysis

Conclusion Conclusion of of

TheThe SensitivitySensitivity AnalysisAnalysis

All the plots generated in this parametric study are All the plots generated in this parametric study are

very useful to optimize perforated completions for very useful to optimize perforated completions for

horizontal wells in horizontal wells in Hassi RHassi R’’melmel Oil Rim, and to predict their Oil Rim, and to predict their

performance within a wide range of reservoir permeability, performance within a wide range of reservoir permeability,

vertical anisotropy and Horizontal anisotropy.vertical anisotropy and Horizontal anisotropy.


Performance of Inverted High Angle Completion

Performance of

« Case Study : HRZ-09 »

Performance of InvertedInverted HighHigh Angle Angle CompletionCompletion

«« Case Case StudyStudy : HRZ: HRZ--0909 »»









WATERWATER

OilOil RimRim

GASGAS

KKavgavg= 500md= 500md

CASE STUDYCASE STUDY

88--13 m13 m

Total Total OilOil RecoveryRecovery = 7.4%= 7.4%

« Case Study : HRZ-09 »«« Case Case StudyStudy : HRZ: HRZ--0909 »»

«« Case Case StudyStudy : HRZ: HRZ--0909 »»

All those factors made the necessity to develop this oil riAll those factors made the necessity to develop this oil rim by m by

implementing horizontal wells, in addition to vertical wells (Miimplementing horizontal wells, in addition to vertical wells (Mixed xed

Development Strategy), to improve the oil recovery in one hand, Development Strategy), to improve the oil recovery in one hand, and and

to alleviate the water and gas coning problems in the other handto alleviate the water and gas coning problems in the other hand..

Among the areas where most horizontal wells have been drillAmong the areas where most horizontal wells have been drilled is ed is

the CTH2 area. This area will be our zone of interest in this stthe CTH2 area. This area will be our zone of interest in this study udy

since the well HRZsince the well HRZ--09 belongs to it. 09 belongs to it.


HRZ-09 HISTORYHRZHRZ--09 HISTORY09 HISTORY

GASGAS

WATERWATER

OilOil RimRim

500m

HR-189

HRE-402

HRE-202

HRE-203

2202m2202m

2214m2214m

HRZ-09 ( ( JanuaryJanuary 2002 )2002 )

2208m2208m



GASGAS

WATERWATEROilOil RR

HRZ-09

2206.94m , 87.90°

imim

HRZHRZ--09 Planned Path09 Planned Path

HRZHRZ--09 Actual Path09 Actual Path

PlannedPlanned GOCGOC

PlannedPlanned WOCWOC (2214m)(2214m)

(2202m)(2202m)



GASGAS

WATERWATEROilOil RR

HRZ-09

imim

HRZHRZ--09 Planned Path09 Planned Path

HRZHRZ--09 Actual Path09 Actual Path

PlannedPlanned GOCGOC

PlannedPlanned WOCWOC (2214m)(2214m)

(2202m)(2202m)


HRZ-09 ACTUAL PATHHRZHRZ--09 ACTUAL PATH09 ACTUAL PATH

HRZ09 Path2175

2180

2185

2190

2195

2200

2205

2210100 200 300 400 500 600 700 800 900 1000

Distance to the East from the Well head, m

TVD

,m

WOC

GOC

TopA


OBJECTIVE OF THE STUDYOBJECTIVE OF THE STUDYOBJECTIVE OF THE STUDY

Because of the difficulty in locating the GOC and WOC contacts Because of the difficulty in locating the GOC and WOC contacts in the in the

CTH2 area, there will probably be other horizontal wells that wiCTH2 area, there will probably be other horizontal wells that will take the ll take the

same profile as that of HRZsame profile as that of HRZ--09.09.

So, it is important to study the performance of this well and tSo, it is important to study the performance of this well and to investigate o investigate

various perforation scenarios in case of inverted high angle provarious perforation scenarios in case of inverted high angle profile. file.

Hence, to come up with the best perforation scheme that guarantHence, to come up with the best perforation scheme that guarantees the ees the

maximum oil recovery, the minimum gasmaximum oil recovery, the minimum gas--oil ratio, and consequently, the oil ratio, and consequently, the

lowest investment cost.lowest investment cost.CASE STUDYCASE STUDY

HRZ-09 HRZ

SIMULATION MODELING

HRZ--09 09

SIMULATION MODELINGSIMULATION MODELING

To study the performance of the well HRZTo study the performance of the well HRZ--09 for different 09 for different

perforation schemes, a simulation modeling of this well is needeperforation schemes, a simulation modeling of this well is needed.d.

A history match is needed for wells that are inside the Model gA history match is needed for wells that are inside the Model grid. rid.

The model Grid, in this case, has to be refined in the vicinityThe model Grid, in this case, has to be refined in the vicinity of the of the

well.well.


RESERVOIR GEOMETRY FOR HORIZONTAL WELL MODEL

RESERVOIR GEOMETRY FOR RESERVOIR GEOMETRY FOR

HORIZONTAL WELL MODELHORIZONTAL WELL MODEL

For this well model, an irregular Cartesian grid was built, aFor this well model, an irregular Cartesian grid was built, and nd

the Cartesian (Xthe Cartesian (X--YY--Z) coordinate are as follow : Z) coordinate are as follow :

•• NumberNumber of blocks in Xof blocks in X--directiondirection 3131

•• NumberNumber of blocks in Yof blocks in Y--directiondirection 1717

•• NumberNumber of blocks in Zof blocks in Z--directiondirection 1414

•• Total Total numbernumber of blocksof blocks 31x17x14 = 737831x17x14 = 7378CASE STUDYCASE STUDY

Layer 5 Layer 5

Layer 4 Layer 4

Layer 14 Layer 14

Layer 1 Gas

Water

Oil R

296m

im

THE PROPOSED PERFORATION SCHEMES

THE PROPOSED THE PROPOSED PERFORATION SCHEMESPERFORATION SCHEMES

1.1. Horizontal Section Perforation (Horizontal Section Perforation (ActualActual Case)Case)




2.2. SlantedSlanted Section PerforationSection Perforation

Layer 5 Layer 5

Layer 4 Layer 4

Layer 14 Layer 14

Layer 1 Gas

Water

Oil Rim




3.3. Horizontal& Horizontal& SlantedSlanted Section Perforation Section Perforation (Double Perforation (Double Perforation SchemeScheme))

Layer 5 Layer 5

Layer 4 Layer 4

Layer 14 Layer 14

Layer 1

296m

Gas

Water

Oil Rim


Comparative Study of

The three Perforation schemes

Comparative Study ofComparative Study of

The three Perforation schemes The three Perforation schemes

In this section, the focus will be on selecting the best In this section, the focus will be on selecting the best

perforation scheme of the three proposed. perforation scheme of the three proposed.

The selection will be based on well performance, especially The selection will be based on well performance, especially

oil recovery and gasoil recovery and gas--oil ratio, as well as economic analysis oil ratio, as well as economic analysis

of the three perforation alternatives.of the three perforation alternatives.



Comparative Study

Based on well Performance

Comparative Study Comparative Study

Based on well Performance Based on well Performance

Comparative Plot of Oil Recovery versus Time for the Three Perforation Schemes

0

2

4

6

8

10

12

14

0 2 4 6 8 10 12 14Time, Years

Oil

Rec

over

y,%

Slanted Section

Horizontal Section (Actual Case)

Slanted & Horizontal Sections(Double Perforation Case)


Comparative Study


Comparative Study Comparative Study


Comparative Plot of Gas-Oil ratio versus Time for the Three perforation Schemes

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0 2 4 6 8 10 12 14Time, Years

GO

R, N

M3/

SM3

Slanted portion

Horizontal Section (Actual Case)

Slanted & Horizontal Sections(Double Perforation Case)

Hence, the actual case (base case) is the most favorable Hence, the actual case (base case) is the most favorable

case according to well performance analysis. This result has to case according to well performance analysis. This result has to

be confirmed by an economic analysis on the three perforation be confirmed by an economic analysis on the three perforation

schemes.schemes.


Comparative Study


Comparative StudyComparative Study


Comparative Study Based On Economic Analysis

Comparative Study Comparative Study Based On Economic Analysis Based On Economic Analysis

The economic analysis in this study is based on the calculationThe economic analysis in this study is based on the calculation of of

the Net Present Value (the Net Present Value (NPVNPV) for each perforation scenario.) for each perforation scenario.

This parameter, This parameter, NPVNPV, provides a convenient measure to select the , provides a convenient measure to select the

best perforation alternativebest perforation alternative

The optimum case is the one that corresponds to the maximum The optimum case is the one that corresponds to the maximum

NPV.NPV.




∑=

×=n

iii RCFNPV

1)(

NPVNPV ::

Where :Where :

(CF)(CF)i i : : Cash Cash FlowFlow in in thethe YearYear ii

RRii : : Discount Rate in Discount Rate in thethe YearYear ii

( ) 111

−+= iRi

τ

ττ : Rate of : Rate of InterestInterestCASE STUDYCASE STUDY



AndAnd assumingassuming thatthat : :

•• Oil Price = 25 $/bblOil Price = 25 $/bbl

•• Rate of Interest, Rate of Interest, ττ = 12%= 12%

KnowingKnowing thatthat in in HassiHassi RR’’melmel OilOil RimRim ::

•• Perforation Cost, Perforation Cost, CpCp = 1,300 $/meter= 1,300 $/meter

•• Cost of Fluid Transport, T = 1.2 $/bblCost of Fluid Transport, T = 1.2 $/bbl

•• Drilling Cost, Drilling Cost, CCDD = 5 MM$= 5 MM$




1. 1. Horizontal Section perforation (Horizontal Section perforation (ActualActual Case)Case)

NPVNPV = 21.05MM$= 21.05MM$Year

Number (i)Year Npi

M.BarrelsIncome Ii

(MM$)Drilling

CostTransport

Cost Cash Flow

(MM$)Discount Rate Ri

(NPV)i (MM$)

1 2003 275.06 6.88 5.40 0.33 1.15 1.00 1.152 2004 275.06 6.88 0 0.33 6.55 0.89 5.853 2005 275.06 6.88 0 0.33 6.55 0.80 5.224 2006 242.57 6.06 0 0.29 5.77 0.71 4.115 2007 132.65 3.32 0 0.16 3.16 0.64 2.016 2008 78.93 1.97 0 0.09 1.88 0.57 1.077 2009 50.64 1.27 0 0.06 1.21 0.51 0.618 2010 35.53 0.89 0 0.04 0.85 0.45 0.389 2011 26.38 0.66 0 0.03 0.63 0.40 0.2510 2012 20.11 0.50 0 0.02 0.48 0.36 0.1711 2013 15.10 0.38 0 0.02 0.36 0.32 0.1212 2014 11.47 0.29 0 0.01 0.27 0.29 0.0813 2015 8.03 0.20 0 0.01 0.19 0.26 0.05

Cumulative 13 1446.58 36.16 5.40 1.73 29.03 21.05




2.2. SlantedSlanted Section perforation Section perforation


Number, iYear NPi

M.BarrelsIncome Ii

(MM$)Drilling

CostTransport

CostCash Flow

(MM$)Discount Rate, Ri

(NPV)i(MM$)

1 2003 171.92 4.30 5.1 0.21 1.01 1.00 1.012 2004 171.92 4.30 0 0.21 4.09 0.89 3.653 2005 171.92 4.30 0 0.21 4.09 0.80 3.264 2006 172.39 4.31 0 0.21 4.10 0.71 2.925 2007 134.52 3.36 0 0.16 3.20 0.64 2.036 2008 92.11 2.30 0 0.11 2.19 0.57 1.247 2009 66.88 1.67 0 0.08 1.59 0.51 0.818 2010 50.64 1.27 0 0.06 1.21 0.45 0.559 2011 40.32 1.01 0 0.05 0.96 0.40 0.3910 2012 33.33 0.83 0 0.04 0.79 0.36 0.2911 2013 27.32 0.68 0 0.03 0.65 0.32 0.2112 2014 22.74 0.57 0 0.03 0.54 0.29 0.1613 2015 19.49 0.49 0 0.02 0.46 0.26 0.12

Cumulative 13 1175.47 29.39 5.10 1.41 22.88 14.61




3. 3. Horizontal & Horizontal & SlantedSlanted Sections perforation Sections perforation


Number, iYear NPi

M.BarrelsIncome, Ii

(MM$)Drilling

CostTransport

CostCash Flow

(MM$)Discount Rate, Ri

(NPV)i(MM$)

1 2003 275.06 6.88 5.50 0.33 1.05 1.00 1.052 2004 275.06 6.88 0 0.33 6.55 0.89 5.853 2005 275.06 6.88 0 0.33 6.55 0.80 5.224 2006 268.58 6.71 0 0.32 6.39 0.71 4.555 2007 148.92 3.72 0 0.18 3.54 0.64 2.256 2008 77.21 1.93 0 0.09 1.84 0.57 1.047 2009 49.49 1.24 0 0.06 1.18 0.51 0.608 2010 33.43 0.84 0 0.04 0.80 0.45 0.369 2011 22.17 0.55 0 0.03 0.53 0.40 0.21

10 2012 13.60 0.34 0 0.02 0.32 0.36 0.1211 2013 8.60 0.21 0 0.01 0.20 0.32 0.0712 2014 5.73 0.14 0 0.01 0.14 0.29 0.0413 2015 4.39 0.11 0 0.01 0.10 0.26 0.03

Cumulative 13 1457.31 36.43 5.50 1.75 29.18 21.37




0

5

10

15

20

25

NPV

, MM

$

Horizontal Section Slanted Scetion Slanted & HorizontalSections

Comparative Histogram of the Three Perforation SchemesOil Price = 25 $/bbl

21.05

14.61

21.37


CONCLUSIONS(CASE STUDY)

CONCLUSIONSCONCLUSIONS(CASE STUDY)(CASE STUDY)

The simulation results indicate that there is no extraThe simulation results indicate that there is no extra--recovery to recovery to

be expected from the double perforation scheme. be expected from the double perforation scheme.

Thus, the best perforation scheme is the one that corresponds toThus, the best perforation scheme is the one that corresponds to

the actual case.the actual case.

Besides, such perforation scheme leads to higher GasBesides, such perforation scheme leads to higher Gas--Oil Ratio to Oil Ratio to

be produced in comparison to the Horizontal section perforation be produced in comparison to the Horizontal section perforation

(actual case). (actual case).




The Economic analysis performed on the three perforation The Economic analysis performed on the three perforation

scenarios has confirmed the above conclusion, which means that scenarios has confirmed the above conclusion, which means that

the maximum net present value (NPV) will correspond to the the maximum net present value (NPV) will correspond to the

actual case if we take into account the investment cost in gas actual case if we take into account the investment cost in gas

facilities.facilities.

Although the well HRZAlthough the well HRZ--09 took an inverted high angle profile 09 took an inverted high angle profile

accidentally, this profile has brought several advantages, accidentally, this profile has brought several advantages,

such as :such as :




Explore the entire oil column and find out the high quality sanExplore the entire oil column and find out the high quality sand of d of

this column prior to placing the horizontal drain. Thus, it servthis column prior to placing the horizontal drain. Thus, it serves as es as

a Pilot Hole.a Pilot Hole.

Alleviate the water and gas coning problems.Alleviate the water and gas coning problems.

Allow the exact location of GasAllow the exact location of Gas--Oil and WaterOil and Water--Oil contacts, so Oil contacts, so

that, the horizontal drain can be placed at a desired depth.that, the horizontal drain can be placed at a desired depth.


CONCLUSIONS CONCLUSIONS

ANDAND

RECOMMENDATIONSRECOMMENDATIONS









CONCLUSIONS CONCLUSIONS CONCLUSIONS

Based on the entire study, the following conclusions can be Based on the entire study, the following conclusions can be

drawn :drawn :

1.1. The perforation length can be reduced, and in many cases, withouThe perforation length can be reduced, and in many cases, without t

a substantial decrease in oil recovery. Moreover, lower a substantial decrease in oil recovery. Moreover, lower values of values of

perforation length lead to lower gasperforation length lead to lower gas--oil ratios produced. oil ratios produced.

2.2. Hence, the perforation length has to be optimized with respect Hence, the perforation length has to be optimized with respect not not

only to oil recovery, but also to gasonly to oil recovery, but also to gas--oil ratio. This to guarantee the oil ratio. This to guarantee the

lowest investment cost in gas facilities.lowest investment cost in gas facilities.

2.2. Hence, the perforation length has to be optimized with respect Hence, the perforation length has to be optimized with respect not not

only to oil recovery, but also to gasonly to oil recovery, but also to gas--oil ratio. This to guarantee the oil ratio. This to guarantee the

lowest investment cost in gas facilities.lowest investment cost in gas facilities.

1.1. The perforation length can be reduced, and in many cases, withoThe perforation length can be reduced, and in many cases, without ut

a substantial decrease in oil recovery. Moreover, lower a substantial decrease in oil recovery. Moreover, lower values of values of

perforation length lead to lower gasperforation length lead to lower gas--oil ratios produced. oil ratios produced.


CONCLUSIONS(Continued)

CONCLUSIONSCONCLUSIONS((ContinuedContinued) )


33.. The reservoir produces more efficiently when the perforation The reservoir produces more efficiently when the perforation

intervals are uniformly distributed along theintervals are uniformly distributed along the wellborewellbore rather rather

than being continuously placed.than being continuously placed.

4. 4. The correlation curves developed in the parametric study can The correlation curves developed in the parametric study can

be used to optimize the perforation scheme for horizontal be used to optimize the perforation scheme for horizontal

wells in wells in Hassi RHassi R’’melmel Oil Rim, especially CTH2 area.Oil Rim, especially CTH2 area.

33.. The reservoir produces more efficiently when the perforation The reservoir produces more efficiently when the perforation

intervals are uniformly distributed along theintervals are uniformly distributed along the wellborewellbore rather rather

than being continuously placed.than being continuously placed.

4. 4. The correlation curves developed in the parametric study can The correlation curves developed in the parametric study can

be used to optimize the perforation scheme for horizontal be used to optimize the perforation scheme for horizontal

wells in wells in Hassi RHassi R’’melmel Oil Rim, especially CTH2 area.Oil Rim, especially CTH2 area.

CONCLUSIONS(Continued)

CONCLUSIONSCONCLUSIONS((ContinuedContinued) )

5. 5. In In Hassi RHassi R’’melmel Oil Rim, the optimum perforation scheme for Oil Rim, the optimum perforation scheme for

horizontal well is the case that corresponds to 60% horizontal well is the case that corresponds to 60%

uniformly distributed perforation.uniformly distributed perforation.

6. 6. Although the well HRZAlthough the well HRZ--09 took an inverted high angle 09 took an inverted high angle

profile accidentally, this profile has brought several profile accidentally, this profile has brought several

advantages. advantages.

5. 5. In In Hassi RHassi R’’melmel Oil Rim, the optimum perforation scheme for Oil Rim, the optimum perforation scheme for

horizontal well is the case that corresponds to 60% horizontal well is the case that corresponds to 60%

uniformly distributed perforation.uniformly distributed perforation.

6. 6. Although the well HRZAlthough the well HRZ--09 took an inverted high angle 09 took an inverted high angle

profile accidentally, this profile has brought several profile accidentally, this profile has brought several

advantages. advantages. CONCLUSIONS CONCLUSIONS

optimization of perforated completions for horizontal wells in...

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