VSD Affinity Laws and Applications

7/31/2019 VSD Affinity Laws and Applications

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Artificial LiftArtificial LiftArtificial LiftArtificial Lift

AE ESP 1 Training, Course 15AE ESP 1 Training, Course 15AE ESP 1 Training, Course 15AE ESP 1 Training, Course 15

04040404----SepSepSepSep----2006 to 292006 to 292006 to 292006 to 29----SepSepSepSep----2006200620062006

Day 5Day 5Day 5Day 5

VSD Affinity Laws

Application of Affinity LawsVSD Applications

AE ESP 15 slide 2

At the end of this section, you will be able to

Use the VSD affinity laws to calculate new performance parameters for the

following equipment.

Understand the affinity laws as they apply to pump properties:

Flow

Head

Power

Efficiency

Shaft Power Limit

And Motors

Nameplate Voltage

Amperage Rating

Power Rating

VSD Affinity Laws


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AE ESP 15 slide 3

VSD Affinity Laws for PumpsVSD Affinity Laws for PumpsVSD Affinity Laws for PumpsVSD Affinity Laws for Pumps

2222

1111RPMRPMRPMRPM

BHPBHPBHPBHP BHPBHPBHPBHPRPMRPMRPMRPM

RPMRPMRPMRPM2222RPMRPMRPMRPM 1111

3

====

HeadHeadHeadHead HeadHeadHeadHeadRPMRPMRPMRPM 2222

RPMRPMRPMRPM 1111RPMRPMRPMRPM2222 1111

2

RPMRPMRPMRPM ====

FlowFlowFlowFlow FlowFlowFlowFlow RPMRPMRPMRPM

RPMRPMRPMRPM

1111

2222

2222 1111RPMRPMRPMRPM RPM RPMRPMRPM====

2222

1111RPMRPMRPMRPM

SBHLSBHLSBHLSBHL SBHLSBHLSBHLSBHLRPMRPMRPMRPM

RPMRPMRPMRPM2222RPMRPMRPMRPM 1111

1

====

AE ESP 15 slide 4

Flow

Head

Power

Efficiency

Shaft Limit

VSD Affinity Laws for PumpsVSD Affinity Laws for PumpsVSD Affinity Laws for PumpsVSD Affinity Laws for Pumps

1

1 0

0

Q Q

=

( ) ( )

2

1

1 1 0 0

0

h Q h Q

=

( ) ( )

3

1

1 1 0 0

0

, ,REQ X REQ X

P Q SG P Q SG

=

1

1 0

0

SBHL SBHL

=

( ) ( )1 1 0 0Q Q =

Independent


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AE ESP 15 slide 5

Pump Laws, Graphical RepresentationPump Laws, Graphical RepresentationPump Laws, Graphical RepresentationPump Laws, Graphical Representation

Assuming 10% increase in Frequency

AE ESP 15 slide 6

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000

Feet

Capacity - Barrels per Day

10

20

30

40

50

60

70

REDA Production Systems

A

GN4000

1.00Rev. Fluid Specific Gravity

Reda Pump Performance Curve

540 Series * - 1 Stage(s)

70 Hz

60 Hz

55 Hz

50 Hz

45 Hz

40 Hz

30 Hz

Pump Laws, MultiPump Laws, MultiPump Laws, MultiPump Laws, Multi----Hz Head CurveHz Head CurveHz Head CurveHz Head Curve


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AE ESP 15 slide 7

Pump Laws, MultiPump Laws, MultiPump Laws, MultiPump Laws, Multi----Hz Power CurveHz Power CurveHz Power CurveHz Power Curve

AE ESP 15 slide 8

VSD Affinity Laws for Motors, ConventionalVSD Affinity Laws for Motors, ConventionalVSD Affinity Laws for Motors, ConventionalVSD Affinity Laws for Motors, Conventional

==== 1111HPHPHPHP2222HPHPHPHP 2222

1111HZHZHZHZ

HZHZHZHZ

==== 1111VoltVoltVoltVolt2222VoltVoltVoltVolt 2222

1111HZHZHZHZ

HZHZHZHZ

==== 1111AAAA2222AAAA


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AE ESP 15 slide 9

VSD AffinityVSD AffinityVSD AffinityVSD Affinity RULESRULESRULESRULES for ALL Motorsfor ALL Motorsfor ALL Motorsfor ALL Motors

Conventional and DominatorConventional and DominatorConventional and DominatorConventional and Dominator

Nameplae

Voltage

Amperage

Rating

Power

Rating

1 0A A=

1

1 0

0

V V

=

11 0

0

AVAIL AVAILP P

=

Ratings

AE ESP 15 slide 10

Motor Laws, GraphicallyMotor Laws, GraphicallyMotor Laws, GraphicallyMotor Laws, Graphically

MotorHorsepow

er

MotorHorsepow

er

MotorHorsepow

er

MotorHorsepow

er

Frequency (hertz)Frequency (hertz)Frequency (hertz)Frequency (hertz)

0000 20202020 40404040 60606060 80808080 1001001001000000

50505050

100100100100

150150150150

200200200200

250250250250

300300300300

350350350350

Graphically it would look like this for a 200 HP, 60 Hz motor:


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AE ESP 15 slide 11

OLDOLDOLDOLD VSD Affinity Laws for Motors, DominatorVSD Affinity Laws for Motors, DominatorVSD Affinity Laws for Motors, DominatorVSD Affinity Laws for Motors, Dominator

Voltage

1 > 60-Hz0, 1 60-Hz

For All Frequencies

Amperage

Power1

1 0

0

AVAIL AVAILP P

=

1 0A A=

1

1 0

0

V V

=

1 60

1

60A A

=

1 60AVAIL AVAILP P=

Like Conventional Special

AE ESP 15 slide 12

Old Dom. Motor Power, GraphicallyOld Dom. Motor Power, GraphicallyOld Dom. Motor Power, GraphicallyOld Dom. Motor Power, Graphically

MotorHorsepow

er

MotorHorsepow

er

MotorHorsepow

er

MotorHorsepow

er


0000 20202020 40404040 60606060 80808080 1001001001000000

50505050

100100100100

150150150150

200200200200

250250250250

300300300300

350350350350


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AE ESP 15 slide 13

Old Dom. Amperage Rating, GraphicallyOld Dom. Amperage Rating, GraphicallyOld Dom. Amperage Rating, GraphicallyOld Dom. Amperage Rating, Graphically

M

otorAmperageRating

M

otorAmperageRating

M

otorAmperageRating

M

otorAmperageRating


0000 20202020 40404040 60606060 80808080 1001001001000000

25252525

50505050

75757575

100100100100

125125125125

150150150150

175175175175

Exercise 2.08Exercise 2.08Exercise 2.08Exercise 2.08

90-Minutes

Work together if you needWe will go over the answers together afterward.

Every single participant is expected to be able to

answer any single question


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AE ESP 15 slide 15

Upon completion of this section, you should be able to:

Combine multiple affinity laws to consider advanced issues

Maximum Safe VSD Speed as limited by

Motor Power

Shaft Power

Housing Pressure Limit

Motor Performance as a function of speed

Motor Load

Expected Amperage

Expected flow from a well

Pump curve intersection with System curve

Application of VSD Affinity Laws

AE ESP 15 slide 16

Maximum Safe Speed: Pump PowerMaximum Safe Speed: Pump PowerMaximum Safe Speed: Pump PowerMaximum Safe Speed: Pump Power ReqReqReqReq

What determines the pump power requirement at a givenfrequency?

What can change when we change the frequency?


-

D725N 1.00

Rev.

50 Hz / 2917 RPM 400 Series - 176 Stage(s) - Sp. Gr.Pump Performance Curve

Optimum Operating RangeNominal Housing DiameterShaft DiameterShaft Cross Sectional AreaMinimum Casing Size

46 - 1234.00

0.6250.3075.500

m3/dinchesinchesininches

Shaft Brake Horsepower Limit

Housing Burst Pressure Limit

StandardHigh StrengthStandardButtressWelded

78125

500060006000

HpHppsipsipsi

0 25 50 75 100 125 150


-

D725N 1.00

Rev.

50 Hz / 2917 RPM 400 Series - 176 Stage(s) - Sp. Gr.Pump Performance Curve

Optimum Operating RangeNominal Housing DiameterShaft DiameterShaft Cross Sectional AreaMinimum Casing Size

46 - 1234.00

0.6250.3075.500

m3/dinchesinchesininches

Shaft Brake Horsepower Limit

Housing Burst Pressure Limit

StandardHigh StrengthStandardButtressWelded

78125

500060006000

HpHppsipsipsi

EffHpMeters

Capacity - Cubic Meters per Day

10%

20%

30%

40%

50%

B.E.P.Q= 95H = 876.82P = 21.08E = 60.25

250

500

750

1,000

1,250

10

20

30

40

50


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AE ESP 15 slide 17

Maximum Safe Speed: Pump vs. MotorMaximum Safe Speed: Pump vs. MotorMaximum Safe Speed: Pump vs. MotorMaximum Safe Speed: Pump vs. Motor


0000 20202020 40404040 60606060 80808080 100100100100

0000

50505050

100100100100

150150150150

200200200200

250250250250

300300300300

350350350350

Power

Power

Power

Power

PAVAIL0

PREQ0

0

1

PAVAIL1 = PREQ1

AE ESP 15 slide 18


Therefore, were looking for 1 such that:

We know from our affinity laws that

11 ),( AVAILXREQ PSGMAXP =

3

0

1

01),(),(

=

XREQXREQ

SGMAXPSGMAXP

=

0

101

AVAILAVAIL PP

Substituting

=

0

1

0

3

0

1

0),(

AVAILXREQ

PSGMAXP

Solving for 1

),(0

001

XREQ

AVAIL

SGMAXP

P =

Valid for any reference

frequency 0


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AE ESP 15 slide 19



0000 20202020 40404040 60606060 80808080 100100100100

0000

50505050

100100100100

150150150150

200200200200

250250250250

300300300300

350350350350

Power

Power

Power

Power

PAVAIL0

PREQ0

0

1

PAVAIL1 = PREQ1

Works going down, too!

AE ESP 15 slide 20

Maximum Safe Speed: Effect of DensityMaximum Safe Speed: Effect of DensityMaximum Safe Speed: Effect of DensityMaximum Safe Speed: Effect of Density


0000 20202020 40404040 60606060 80808080 100100100100

0000

50505050

100100100100

150150150150

200200200200

250250250250

300300300300

350350350350

Pow

er

Pow

er

Pow

er

Pow

er

PAVAIL0

PREQ0

0

1

PAVAIL1 = PREQ1


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AE ESP 15 slide 21

Maximum Safe Speed:Maximum Safe Speed:Maximum Safe Speed:Maximum Safe Speed: Old DominatorOld DominatorOld DominatorOld Dominator


0000 20202020 40404040 60606060 80808080 100100100100

0000

50505050

100100100100

150150150150

200200200200

250250250250

300300300300

350350350350

Power

Power

Power

Power

PAVAIL0 > PREQ0

PREQ0

0

1

PAVAIL1 = PREQ1 (> 60)

PAVAIL0 < PREQ0

PAVAIL1 = PREQ1 (< 60)

AE ESP 15 slide 22

Motor LimitMotor LimitMotor LimitMotor Limit OldOldOldOld Dominator LawsDominator LawsDominator LawsDominator Laws The process to determine the maximum safe speed for a dominator is the

same:

Equate PAVAIL1to PREQ1 Substitute in appropriate affinity law

Solve for 1 Because the affinity law for motor power rating changes at 60-Hz, the

formulas will change:

SpecialSame as normal

1 > 60-Hz0, 1 60-Hz

),(0

001

XREQ

AVAIL

SGMAXP

P =

=

0

101

AVAILAVAIL PP 601 AVAILAVAIL PP =

3

1

60

601

),(60

=

XREQ

AVAIL

SGMAXP

P


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AE ESP 15 slide 23

Motor LimitMotor LimitMotor LimitMotor Limit Old DominatorOld DominatorOld DominatorOld Dominator Rule vs. NormalRule vs. NormalRule vs. NormalRule vs. Normal

Frequency (hertz)Frequency (hertz)Frequency (hertz)Frequency (hertz)0000 20202020 40404040 60606060 80808080 100100100100

0000

50505050

100100100100

150150150150

200200200200

250250250250300300300300

350350350350

DominatorDominatorDominatorDominator

MotorMotorMotorMotor

HorsepowerHorsepowerHorsepowerHorsepower

Frequency (hertz)Frequency (hertz)Frequency (hertz)Frequency (hertz)0000 20202020 40404040 60606060 80808080 100100100100

0000

50505050

100100100100

150150150150

200200200200

250250250250

300300300300

350350350350

StandardStandardStandardStandard

MotorMotorMotorMotor

HorsepowerHorsepowerHorsepowerHorsepower

AE ESP 15 slide 24

Shaft LimitShaft LimitShaft LimitShaft Limit


0000 20202020 40404040 60606060 80808080 100100100100

0000

50505050

100100100100

150150150150

200200200200

250250250250

300300300300

350350350350

Pow

er

Pow

er

Pow

er

Pow

er

SBHL0

PREQ0

0

1

SBHL1 = PREQ1


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AE ESP 15 slide 25

Maximum Safe Speed: Shaft Rating vs. PowerMaximum Safe Speed: Shaft Rating vs. PowerMaximum Safe Speed: Shaft Rating vs. PowerMaximum Safe Speed: Shaft Rating vs. Power ReqReqReqReq



11 ),( SBHLSGMAXP XREQ =

3

0

1

01),(),(

=

XREQXREQ

SGMAXPSGMAXP

=

0

101

SBHLSBHL

Substituting

=

0

1

0

3

0

1

0 ),(

SBHLSGMAXP XREQ

Solving for 1

),(0

001

XREQSGMAXP

SBHL =


frequency 0

AE ESP 15 slide 26

Housing Pressure LimitHousing Pressure LimitHousing Pressure LimitHousing Pressure Limit


0000 20202020 40404040 60606060 80808080 100100100100

0000

1000100010001000

2000200020002000

3000300030003000

4000400040004000

5000500050005000

6000600060006000

7000700070007000

Press

ure

Press

ure

Press

ure

Press

ure

PH,MAX

P(Q=0)0

0

1

P(Q=0)1 = PH,MAX


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AE ESP 15 slide 27

Maximum Safe Speed: Housing PressureMaximum Safe Speed: Housing PressureMaximum Safe Speed: Housing PressureMaximum Safe Speed: Housing Pressure



MAXHPQP ,1)0( ==

2

0

1

01)0()0(

===

QPQP

Substituting

MAXHPQP

,

2

0

1

0)0( =

=

Solving for 1

0

,

01)0( =

=QP

PMAXH


frequency 0

AE ESP 15 slide 28

Overall Speed LimitOverall Speed LimitOverall Speed LimitOverall Speed Limit

For a given system (pump, motor), we need to consider allpossible limits:

Motor

Shaft

Housing Pressure

The limit with the lowest safe speed is the maximum safespeed.


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AE ESP 15 slide 29

Comparing Limits, graphicallyComparing Limits, graphicallyComparing Limits, graphicallyComparing Limits, graphically


0000 20202020 40404040 60606060 80808080 100100100100

0000

50505050

100100100100

150150150150

200200200200

250250250250

300300300300

350350350350

Power

Power

Power

Power

SBHL0

PREQ0

0

1

SBHL1 = PREQ1

PAVAIL1 = PREQ1

PAVAIL0

P(Q=0)0

1000100010001000

2000200020002000

3000300030003000

4000400040004000

5000500050005000

6000600060006000

7000700070007000

PH,MAX

P(Q=0)1 = PH,MAX

AE ESP 15 slide 30

Overall Speed Limit: ExampleOverall Speed Limit: ExampleOverall Speed Limit: ExampleOverall Speed Limit: Example

Consider the following example:

Pump: GN2100X135

Ref. Frequency (0) = 60-Hz

Avg. SG = 1.04

PREQ0(Max, 1.04) = 150-HP

P(Q=0)0 = 3370-psi

SBHL0 = 256-HP (standard shaft)

PH,MAX = 5000-psi (V-thread)

PAVAIL0 = 200-HP


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AE ESP 15 slide 31

Overall Speed Limit: ExampleOverall Speed Limit: ExampleOverall Speed Limit: ExampleOverall Speed Limit: Example

Max. Speed according to motor:

HzSGMAXP

PMotorXREQ

AVAIL=== 2.69

150200)60(

),()(

0

001

Max. Speed according to shaft:

Max. Speed according to housing:

Overall Max. Safe Speed: 69.2-Hz

Limit for Safe Speed: Motor

HzSGMAXP

SBHLShaft

XREQ

=== 3.78150

25660

),()(

0

001

HzQP

PHous

MAXH==

== 0.73

3370

500060

)0()(

0

,

01

(these values approximate the graphical example)

AE ESP 15 slide 32

Motor Performance: LoadMotor Performance: LoadMotor Performance: LoadMotor Performance: Load

Consider that

AVAIL

REQ

P

PLoad=

0

0

0

AVAIL

REQ

P

PLoad =

1

1

1

AVAIL

REQ

P

PLoad =

At 0 we can specify:

And at 1 we can specify:


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AE ESP 15 slide 33

Motor Performance: LoadMotor Performance: LoadMotor Performance: LoadMotor Performance: Load

But we can substitute in for PREQ1 and PAVAIL1 using the

pump and motor affinity laws

=

0

10

3

0

10

1

AVAIL

REQ

P

P

Load

2

0

101

=

LoadLoad


0000 20202020 40404040 60606060 80808080 1001001001000000

20202020

40404040

60606060

80808080

100100100100

120120120120

140140140140

Load

Load

Load

Load

Load0

This is not accurate enough

for real calculations, but is an

acceptable approximation

AE ESP 15 slide 34

Motor AmperageMotor AmperageMotor AmperageMotor Amperage

If we assume that actual running amperage is proportional

to load, then we can write:

LoadI

And then we can conclude that:

2

0

101

=

II

0000 20202020 40404040 60606060 80808080 1001001001000000

0.20.20.20.2

0.40.40.40.4

0.60.60.60.6

0.80.80.80.8

1.01.01.01.0

1.21.21.21.2

1.41.41.41.4

I/AI/AI/AI/A

I0/A

This is a very bad

assumption for detailed

calculations and should

only be used as an

approximation


Approx.

True


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AE ESP 15 slide 35

Flow rate and FrequencyFlow rate and FrequencyFlow rate and FrequencyFlow rate and Frequency

We understand the relationship between pumpcharacteristics and frequency:

What about expected flow rate?


90-Minutes





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AE ESP 15 slide 37

Upon completion of this section, you should be able to:

Solve for frequency with a known pump and a target wellcondition

Size a motor to work at an abnormal frequency

Design a Pump to work appropriately for a range of flow rateswith given well performance

Design a Pump to cover potentially changing conditions from awell over time.

Design a Pump to cover a large range of potential operatingconditions with uncertain well performance

VSD Applications

AE ESP 15 slide 38

Solving for design frequencySolving for design frequencySolving for design frequencySolving for design frequency

For our pump designs so far, we followed a rigidprocedure:

Establish target conditions

Select Appropriate Pump

Select the required number of stages to achieve the target

conditions


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AE ESP 15 slide 39

Solving for design frequencySolving for design frequencySolving for design frequencySolving for design frequency

But what if we cant design a custom pump?

Need to work with whats in inventory

The number of desired stages isnt available

Right pump, too many stagesRight pump, too many stagesRight pump, too many stagesRight pump, too many stages

Wrong Pump,Wrong Pump,Wrong Pump,Wrong Pump,

But closeBut closeBut closeBut close

This is when a VSD is very useful:This is when a VSD is very useful:This is when a VSD is very useful:This is when a VSD is very useful:

We can change the pump curve toWe can change the pump curve toWe can change the pump curve toWe can change the pump curve tomatch our requirements bymatch our requirements bymatch our requirements bymatch our requirements bychanging the operating frequencychanging the operating frequencychanging the operating frequencychanging the operating frequency

AE ESP 15 slide 40

Solving For FrequencySolving For FrequencySolving For FrequencySolving For Frequency

So how are we going to find our frequency to make ourpump work in our target conditions?

You cant solve for it using formulas.

Using PAD

Change the frequency or RPM until

the head curve matches yourrequirement.

Using frequency you can

only go to nearest 1-Hz.

56565656----HzHzHzHz 60606060----HzHzHzHz


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AE ESP 15 slide 41

Solving For FrequencySolving For FrequencySolving For FrequencySolving For Frequency Using PAD

If you have NO IDEA, you can use the multi-Hz plot:

0 1,000 2,000 3,000 4,000 5,000 6,000

Feet


2,500

5,000

7,500

10,000

12,500


A

SN3600

1.007.000Rev. Fluid Specific Gravity


538 Series - 172 Stage(s)

Minimum Casing Size OD Check Clearances

65 Hz

60 Hz

55 Hz

50 Hz

45 Hz

But Make sure you go back and double-check after!

AE ESP 15 slide 43

VSD ApplicationsVSD ApplicationsVSD ApplicationsVSD Applications Motor SizingMotor SizingMotor SizingMotor Sizing Now that your pump is sized, you need to select your motor.

Determine your power requirementpower requirementpower requirementpower requirement at your design frequency.

Power

Power

Power

Power

HzHzHzHz

Use the MOTOR POWER RATING affinity law to correct this powerpowerpowerpowerto a

reference frequency (60-Hz, 50-Hz)

Select the smallest motor with a power ratingpower ratingpower ratingpower rating larger than your power

requirement at reference frequency

Use the MOTOR POWER RATING affinity law to correct your motormotormotormotorpowerpowerpowerpower back to design frequency.

Calculate motor load.


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AE ESP 15 slide 44

ExampleExampleExampleExample Finding FrequencyFinding FrequencyFinding FrequencyFinding Frequency


90-Minutes





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AE ESP 15 slide 46

Flow Rate RangeFlow Rate RangeFlow Rate RangeFlow Rate Range

The second typical application for a pump with a VSD is to

consider a flow rate range for a well with establishedproductivity.

For example

My client gives me her well data that determines inflow and

says that it is very accurate.

But shes not sure what flow rate she wants from the well.

But she does know that she wants to produce anywhere

from some minimum flow rate to some maximum flow rate

without changing the pump.

So what do we do?

AE ESP 15 slide 47


Lets start by considering the system curve.

QQQQMAJMAJMAJMAJQQQQMINMINMINMIN

TDHTDHTDHTDH MAJMAJMAJMAJTDHTDHTDHTDH MINMINMINMIN

And then lets establish some goals:

Reasonable efficiency for the whole flow range.

Reasonable flow rates (relative to ROR) for whole flow range.

Reasonable frequencies for whole flow range.


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AE ESP 15 slide 48


And lets consider the implications of the relative position of

our two points: The higher flow-rate point will have a higher design frequency

The higher flow-rate point will have a higher power

requirement

QQQQMAJMAJMAJMAJQQQQMINMINMINMIN

TDHTDHTDHTDH MAJMAJMAJMAJTDHTDHTDHTDH MINMINMINMIN

Our QMAJ,

therefore, ismuch more

important from

a designstandpoint.

AE ESP 15 slide 49


So that gives us some guidance:

Choose an operating frequency for the major flow point.

Design a pump like normal emphasizing high efficiency and

near BEP (remember, we can customize frequency!)

Then were going to solve for minimum frequency just like in

our first VSD application

And we will review our operating point at QMINto see if werehappy. If not, we tweak the design (stages and frequency)

0 1,000 2,000 3,000 4,000 5,000 6,000

Feet


2,500

5,000

7,500

10,000

12,500


A

SN3600




Minimum Casing Size ODCheck Clearances

65 Hz

60 Hz

55 Hz

50 Hz

45 Hz


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AE ESP 15 slide 50


Some notes on variable rate applications

A dead well system curve cuts across the multi-frequencyhead plot from left to right at increasing Q/BEP ratios.

The lower flow rate, therefore, will nearly always be further

left from BEP than the higher flow rate.

0 1,000 2,000 3,000 4,000 5,000 6,000

Feet


2,500

5,000

7,500

10,000

12,500


A

SN3600





65 Hz

60 Hz

55 Hz

50 Hz

45 Hz

Make sure youcalculate allrelevant informationat each operatingpoint.

For very large flow

rate ranges, it may

not be possible to

keep your lower rate

within the ROR.

AE ESP 15 slide 51

ExampleExampleExampleExample Flow Rate RangeFlow Rate RangeFlow Rate RangeFlow Rate Range


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90-Minutes




AE ESP 15 slide 53

Changing ConditionsChanging ConditionsChanging ConditionsChanging Conditions

Another application for a VSD is for a well where the ESPis will last a long time.

In such a well, we will need to take into consideration theexpected change in well conditions over the life of the ESP.

Things that will definitely change over time:

Reservoir Pressure

Well Productivity

Average Fluid Density

To figure out what to do, as always, we start with


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AE ESP 15 slide 54

Changing Conditions on System CurveChanging Conditions on System CurveChanging Conditions on System CurveChanging Conditions on System Curve

Consider the following example for a well with a target PWF.

We expect the following significant changes in our wellfrom now until the expected run life

QQQQMAX0MAX0MAX0MAX0QQQQMAX1MAX1MAX1MAX1

PPPPR0R0R0R0

PPPPR1R1R1R1

Decreased Static

Pressure

Decreased

Productivity

Increased Water cut

(and therefore avg.

Density)

Target PWF

AE ESP 15 slide 55

0 1,000 2,000 3,000 4,000 5,000 6,000

Feet


2,500

5,000

7,500

10,000

12,500


A

SN3600





65 Hz

60 Hz

55 Hz

50 Hz

45 Hz

Changing ConditionsChanging ConditionsChanging ConditionsChanging Conditions After that, the process is basically the same as the flow

rate range application

Pick one of the two points and design a pump

Solve for the operating frequency for the second point

Adjust your design if youre not happy

Things to Remember

Harder to pick starting

point

Higher Flow rate may

not mean higher

frequency

Optimizing present

production is usually

more important than

future production


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AE ESP 15 slide 56

ExampleExampleExampleExample Changing ConditionsChanging ConditionsChanging ConditionsChanging Conditions


90-Minutes





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AE ESP 15 slide 58

Unknown ProductivityUnknown ProductivityUnknown ProductivityUnknown Productivity

Our last VSD application is to use a VSD to cover a range

of potential conditions when the exact well performance isunknown.

This application is surprisingly common:

New well drilled in a mature formation

Re-perforated well

After workover or stimulation

First time installing an ESP in the well

Big increase in drawdown and uncertain expectations on

results

So where do we start?

AE ESP 15 slide 59


Though the wells productivity may be unknown, we canusually get an estimate or range of potential productivity:

Net-pay comparison

from wells in the

same reservoir

Skin range

combined with

theoretical well

performance

High tolerance

based on limited

well drawdown to

this point.

QQQQMAX/MAXMAX/MAXMAX/MAXMAX/MAXQQQQMAX/MINMAX/MINMAX/MINMAX/MIN

PPPPRRRR


30/32

30

AE ESP 15 slide 60


Once we have established a range on potential inflow

conditions, we can establish some PWF targets:

Optimize production

Formation Limits


PPPPRRRR

And though our

Inflow is

uncertain, our

outflow is well

defined by well

conditions

AE ESP 15 slide 61


So now we combine our variable inflow with our outflow toestablish a system range for our pump:


PPPPRRRR


31/32

31

AE ESP 15 slide 62


From there, our procedure is the same as before:

Our maximum point is the most important for efficiency and

power requirement, so we use that as a starting point.

Then we solve for the operating frequency of the other

points.

And we review the intersection of our potential operating

range with our pump multi-frequency curve.

If were not happy

We need to tweak our design until we are satisfied.

Adjust pump style, # stages, frequency

Once we have decided on our pump, then we size our motor

on our max flow point.

AE ESP 15 slide 63


Reviewing on the Multi-Hz plot:

0 1,000 2,000 3,000 4,000 5,000 6,000

Feet


2,500

5,000

7,500

10,000

12,500


A

SN3600





65 Hz

60 Hz

55 Hz

50 Hz

45 Hz


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AE ESP 15 slide 64

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90-Minutes




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VSD Affinity Laws and Applications