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Virtual Session 2
Electrical Submersible Pumps Fundamentals
Manual Design
ESP Design Example
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
©2016 PetroSkills. all rights reserved PetroSkills, LLC_________________________________________________________________________________________________________
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ESP Design and Equipment Selection: Nine Steps**
1. Basic data
2. Production capacity
3. Gas calculations
4. Total dynamic head
5. Pump type
6. Optimum size of components
7. Electric cable
8. Accessories and optional equipment
9. Variable speed drive
** Centrilift
Data Collection
1. Well Data• Casing or liner size and weight API CASING 7 IN.
O.D. 29 #/FT. (ID 6.184 in, Drift ID 6.059 in.) Set at 7100 Ft.
• Tubing size, type and thread:, API TUBING 2-7/8 IN. O.D. EUE 8 RD THREADS (NEW), 6.5 lb/ft. (ID 2.441 in., Coupling OD 3.668 in.)
• Perforated or open hole interval 6950 – 7050 Ft. (2118.4 – 2148.8 m)
• Pump setting depth (measured & vertical) 6500 Ft. (1981.2 m)
• Well Deviation Survey VERTICAL WELL
2. Production Data• Wellhead tubing pressure 100 PSIG (689.475 kPa)
• Wellhead casing pressure NA
• Present production rate
• Producing fluid level and/or pump intake
• pressure
• Static bottom-hole pressure 3000 PSI (20684.27 kPa)
• EST LIQ PI 1.4 BPD/PSI dp (0.0323 m3/d/kPa)
• Datum point 7000 FT (2133.6 m)
• Bottom-hole temperature 200 °F (93 °C)
• Desired production rate 2400 STBPD (381.568 m3/day)
• Gas-oil ratio FGOR = 250 SCF/STB (44.5 m3/m3)
• Water cut 80%
4. Well Fluid Conditions• Specific gravity of water 1.06
• Oil API or specific gravity 35 °API
• Specific gravity of gas 0.75 (Air = 1.0)
• Bubble-point pressure 1250 psig (8618.446 kPa)
• Viscosity of oil
• PVT data
5. Power Sources• Available primary voltage 12,470 VOLTS
THREE PHASE
• Frequency 60 Hz
• Power source capabilities
6. Possible Problems• Sand
• Deposition
• Corrosion
• Paraffin
• Emulsion
• Gas
• Temperature
• Other constraints (if any)
NONE EXPECTED
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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Production Capacity
Using the PI of 1.4 BPD/psi (0.03228 m3/d/kPa) calculate PwfPwf = 3000 – (2400/1.4) = 1286 psi (8866.658 kPa)
The Pwf > Pbp, hence use of PI method is good
Calculate Pump intake pressureFluid SG = (0.8*1.06)+(0.2*0.85) = 1.02Pump intake pressure, PIP = Pwf – {(Head, ft * SG)/2.31 ft/psi }PIP = 1286 – {(500 * 1.02)/2.31} = 1065 psi (7342.916 kPa)
As PIP<Pbp, there will be some free gas at intake
Gas Calculations (1)
** Solution gas oil ratio (Rs) at pump intake:
• Substituting PIP (1065 psi) in place of Pb for pump intake conditions, Rs= 208 scf/STB
Calculate Bo (FVF) using Rs found above using Standing eqn
• F = 452.86 and Bo = 1.17 RB/STB
**Note: The Rs and Bo at pump intake can also be estimated from Standing Correlation Charts or from PVT software packages of Nodal analysis.
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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Example:GOR = 250 scf/stbSGgas = 0.75Oil Gravity = 35o APIBHT = 200o F
Standing’s Correlation – Bubble Point Pressure
Pbp = 1300 psia**
Example:GOR = 250 scf/stbSGgas = 0.75Oil Gravity = 35o APIBHT = 200o F
**Pbp value already supplied as 1265 psia
Finding the Bubble Point pressure starting with Solution GOR
Example:GOR = 250 scf/stbSGgas = 0.75Oil Gravity = 35o APIBHT = 200o F
Standing’s Correlation – Bubble Point Pressure
Example:GOR = 250 scf/stbSGgas = 0.75Oil Gravity = 35o APIBHT = 200o F
PIP = 1080 psia**
Using the Bubble Point correlation to estimate the GOR at pump intakeExample:GOR = 250 scf/stbSGgas = 0.75Oil Gravity = 35o APIBHT = 200o F
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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Example:GOR = 250 scf/stbSGgas = 0.75Oil Gravity = 35o APIBHT = 200o F
Standing’s Correlation – Oil Formation Volume Factor
Bo = 1.17 reservoir bbl/STB
Example:GOR = 250 scf/stbSGgas = 0.75Oil Gravity = 35o APIBHT = 200o F
Finding Bo for pump inlet conditions
Gas Calculations (2)
Determine gas volume factor (Bg) as follows:
Assuming 0.85 Z Factor and using the reservoir temperature (200°F or 660°R at pump intake), Bg = (5.04*0.85*660)/1080= 2.62 bbl/Mscf
Volume of free gas at pump intake:
TG = (STBOPD * FGOR)/1000 Mscf• Tg = (2400*0.2) * 250 / 1000 = 120 Mscf/d
Solution gas using Rs at pump intake, • Sg = (STBOPD * Rs)/1000 = (480*208)/1000 = 100 Mscf/d
Volume of free gas at pump intake• Fg = Tg – Sg = 120 – 100 = 20 Mscf/d
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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Gas Calculations (3)
Volume of oil (Vo) at pump intake• Vo = STBOPD * Bo (RB/STB) = 480 * 1.17 = 561.6 BOPD
Volume of free gas at pump intake• Vg = Fg Mscf * Bg bbl/Mscf = 20 * 2.62 = 52.4 BGPD
Volume of water at pump intake• Vw = STBLPD * BSW = 2400*0.8 = 1920 BWPD
Total volume of oil gas water at intake • Vt = Vo + Vg + Vw = 2534 BFPD• This is the volume the ESP should be designed for.
Percentage of free gas present at pump intake, GVF= (52.4/2534)*100 = 2%. Gas separator is not required (<10%)
Note: The reduction of composite fluid gravity due to presence of gas should be accounted for horsepower calculations if the gas fraction is high
Frictional Head Loss Using Chart
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Total Dynamic Head
Calculate TDH (feet) as
TDH = Hd + Ft + PdFor the Design Example:• Assume Surface casing pressure : 0 psig • Mid perf depth : 7000 ft. (2133.6 m)
• Pump set depth: 6500 ft. (1981.2 m)
• FLOP = 2410 ft. (734.568 m)
• Dynamic fluid level, Hd : 4090 ft (1246.632 m)
• For 2534 BFPD and 2-7/8” new tubing, Pipeline frictional loss = 48*6.5 = 312 ft (95.097 m)
• Ft = 312 ft (95.097 m)
• Assume Flowing wellhead pressure = 100 psig (689.475 kPa)
• Pd = 100 * (2.31/1.02) = 226 ft (68.884 m)
• TDH = 4090 + 312 + 226 = 4628 ft. (1410.614 m)
Pump Discharge Pressure
Example:
TDH = 4628 ft = 2048 psi (14120.46 kPa)
PDP = PIP + Pump ∆P
PDP = 1065 + 2048 = 3113 psi (21463.38 kPa)
(PDP)3113 psig
(PIP)1065 psig
(Pwf)1286 psig
FWHP100 psig Pressure
Dep
th,
Ft
TV
D
Pump Depth
Mid-perf Depth
6500
7000
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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Equipment Combination Sizing Options
Pump Type Selection
Preliminary Equipment Combination Selection• Pump Size 538 Series (Pump OD: 5.38 in.)• Protector Size 513• Motor Size 562
538P23 pump has good efficiency at 2550 BFPD
Also take into account of• Fluid characteristics, gas, viscosity; • Well Conditions, Abrasives, Scale etc.• Radial flow Type / Floater construction may be sufficient for this
application
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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Pump Performance Curve
Determination of Pump Stages
From the Pump Curve • Head = 51.5 ft (15.697 m) per stage• Number stages = TDH / (Head per stage)• Number stages = 4628 / 51.5 = 90 stages• Using pump technical data, a pump housing with 90+ stages should
be selected
From the Pump Curve • Horse power = 1.5 HP per stage
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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Pump Housing Options
Pump Housing Selection
From the Pump Curve • Head = 51.5 ft (15.697 m) per stage• HP = 1.5 HP per stage• Number stages = TDH / (Head per stage)• Number stages = 4628 / 51.5 = 90 stages• Using pump technical data, Housing no.7 with 95 stages capacity
will be selected
Horse power requirement• Brake Horse Power = BHP per stage * No. of Stages * Sp. gravity• BHP = 1.5* 95 * 1.02 = 145 HP
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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Selection of Pump intake, Seal Sections
Pump Intake:
Separator not required for initial conditions• Consider life of the well operations; include separator if needed and
estimate HP requirements
Select suitable pump intake if separator not needed
Seal Section:
Select 513 Series suitable seal section (housing OD: 5.13 in.)
Add the HP required for the seal section and estimate total HP requirement
Check Max Pressure / HP Limits
Housing Burst Pressure Limit• With closed discharge, head developed = 71 ft/stage• Max head developed by pump = 71*95 = 6745 ft. (2055.876 m)
• Max pressure developed by pump = 2981 psi (20553.27 kPa)
• The pump housing pressure rating = 5600 psi (38610.64 kPa)
Housing burst pressure limit not exceeded
Shaft HP • Pump and Gas separator HP limit = 360 HP (max for Standard shaft,
60 Hz supply)• Actual = 145 HP Shaft HP limit not exceeded
Check Seal / Protector Design• Total thrust generated by pump = S/I Pump PSI x Shaft area
= 2981 * 0.6016 sq in. (Shaft dia is 7/8”) = 1793 pounds (813.3 kg)
• Make sure the selected seal can withstand beyond this limit
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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Selection of Motor
Selection of Motor
Select the high voltage (thus low current) motor that will have lower cable losses, thus requiring smaller conductor size cables
For the well temperature (200°F), for the 60 Hz service, a 562 KMHJ Series should be sufficient
Referring to the Technical Data on Motors, the next higher power motor is 161 HP
Of the three options available for the 161 HP, the motor with 1406 Volts, 72 amps will be used
• All operating parameters are well within their recommended ranges (e.g. thrust bearing, shaft HP, housing burst pressure and fluid velocity).
• Single motor is sufficient
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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Selection of Cable Size
Applying Temperature Correction
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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Electric Cable Size
The proper cable size is governed by the motor amperage, voltage drop, and space available between the tubing collar and casing drift
Guideline is to select a cable size with a voltage drop of less than 30 volts per 1,000 ft. (304.8 m)
For the motor amps (72 A) Cable #2 has a voltage drop of 21 x 1.26 = 26.5 volts/1,000 ft. (304.8 m) and will be selected
Selection of Cable Insulation Type
Ranking of insulation materials
Model Max Tdeg. F
Min Tdeg. F
Flat Round
Insulation Jacket Application
CTT 190 -40 F Thermo-plastic
Thermo-plastic
Shallow wells, Water wells, Low CO2 Light ends
CPN 205 -30 F/R Poly-propylene
Nitrile General
CPL 225 -40 F Poly-propylene
Lead Gassy Wells, High CO2 H2S
CEN 280 -30 F/R EPDMw/Tape
Nitrile Low to Moderate Gassy Conditions
CEE 400 -60 F/R EPDM EPDM w/Tape, Braid
Moderate Gassy
CEB 300 or 400 R EPDMw/Extruded Fluro-polymer
EPDM Gassy Wells
CEL 450 -40 F/R EPDM Lead w/Bedding Tape
Hot Gassy Wells
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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Electric Cable
Cable # 2 has been selected• Estimated voltage drop of 26.5 volts/1,000 ft. (304.8 m)
• Insulation Spec: CENR (Centrilift EPDM, Nitrile, Galvanized Armor, Round):
Surface voltage required = Nameplate voltage + Cable loss
= 1406 + (26.5*6.6) = 1581 V (using 100 ft cable more than the ESP set depth)
Also calculate length of flat cable (MLE) required
Size AWG KV Rating Nominal Dimension Weight
2 5 1.31 in. (33.3 mm) 1.51 lb/ft (2.25 Kg/m)
Accessories
Accessories:
The flat guards cable bands and other downhole accessories will be ordered
Downhole gauge equipment
Wellhead feedthrough
A cable vent box must be installed between the wellhead and the motor controller to prevent gas migration to the controller
Motor controller:
KVA = (Surf voltage * Amps *1.732)/1000
= (1581*72*1.732)/1000 = 197.2
The need for VSD should be investigated for current conditions as well as near future conditions and ordered as required
Transformer and surface cable should be ordered
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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Recall - the surface set up options
Switchboard
Variable Speed Drive (VSD)
Generation System
Step-downTransformer
Switchboard Junction Box ESP
high voltageInput power(11-15kV)
250 – 4000V input atfixedfrequency(50/60 Hz)
high voltage input power (11-15kV)
380V or 480 V input at fixed frequency (50/60 Hz)
380V / 480 V output at desiredfrequency
output voltage for ESP at desired frequency
Generation System
Step-downTransformer
Variable Speed Drive
Step-up Transformer
Junction Box
ESP
ESP Sizing Summary
The basic ESP sizing process is as follows:1. Assume a design flowrate (STB/day), water-cut, WHP, ESP setting
depth and IPR 2. From the IPR, determine Pwf3. Calculate upwards to find PIP 4. Calculate downwards from WHP to find PDP 5. Calculate pump P = PDP – PIP 6. Pump TDH (ft) = Pump P / Fluid gradient (psi/ft)7. Find average flowrate (Qpump) in pump (RB/day), this includes oil
gas and water volumes, all in BBL/day8. Select pump size from casing I.D. and pump operating range9. From pump operating curves, read head per stage delivered at
Qpump10.Calculate no. of stages required = TDH / (head per stage)11.From pump operating curves, read power required per stage at
Qpump
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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ESP Sizing Summary (2)
12.Calculate total motor horsepower required = power per stage x no. of stages x fluid S.G.
13.Select appropriate protector (seal) configuration 14.Evaluate requirement for gas separator15.Select voltage/amps combination for selected motor size16.Select cable size from amps required 17.Specify cable protectors or banding for cable18.Determine KVA rating of switchboard or VSD19.Review the calculations if VSD is opted for, and make necessary
changes20.Order additional equipment (e.g., Wellhead feedthrough, Vent box,
Downhole data package, etc.) as required
Note: The completion will become more complex if a production packer / Y-tool or smart elements are included
Precautions and Procedures
ESP Start up
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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ESP Commissioning Precautions
Unit to be started in a controlled manner and closely observed till it stabilizes
Useful tools for monitoring: • Downhole pressure sensor• Surface pressure gauge and choke
Historical settings: • Overloads set at about 115% • Under-loads at 80%
– It may be necessary to adjust this during start up
Of the normal running current
ESP Commissioning Guidelines
1. Set the in-line valves in the correct position
2. If the well is flowing before starting the unit, the flow must be stopped by closing the choke
3. If the well was killed using heavy kill fluid then the amperage will be high while pumping the high density fluid. The current has to be carefully monitored until the kill fluid has been removed from tubing
4. ESP turning in correct direction will be confirmed by surface pressure (pump should not be back-spinning)
5. If current is getting too high or fluctuating in a manner which is causing concern, then the motor should be shut down and the problem investigated
6. Test the well to know the producing rate – Ensure pump is operating within the recommended operating range• Control production rate using choke if required
7. Observe the parameters vs. time in a chart
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0
10
40
50
60
70
90
100
500
2000
2500
300080
3500
Current Wellhead Temperature Wellhead Pressure Intake Pressure Discharge Pressure
ESP Start
First Indicationof Flow
Controlling Pressure with Choke
Take Note of Shut-In SuctionPressure
Both Pressures decrease
DischargePressure
IntakePressure
Wellhead Pressure
Current
150030
20
1000Wellhead Temperature
Example: ESP Commissioning Chart
ESP Routine Start
If the unit was stopped, wait for 30 minutes before restarting
Observe the ESP performance in the chart
All data are important when starting units
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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0
30
50
60
90
100
500
201000
10
40
1500
2000
2500
3500
Current Wellhead Temperature Wellhead Pressure Intake Pressure Discharge Pressure
Normal RunningConditions
Min 30 Minutewait
ESP Start
300080
First Indication of Flow
70
Controlling Pressure with Choke
Check Pressure has Equalised
Example: ESP Routine Start-up
The detailed design for ESP system was demonstrated with a well example
• Should accommodate the production requirements for a reasonable period (3-4 years). Possible changes production rate, GOR, water cut etc. during this period should be factored in
• Lot of communication and information-sharing between various teams of the operator and with the ESP supplier will be required
The ESP commissioning / start up procedure was reviewed
There is significant value in reviewing the ESP and well parameters together to achieve long run life and profitable operations
Session Summary
ESP design to accommodate
required flexibility
Good surveillance required during
start up and running of ESP
Production and Completions_________________________________________________________________________________________________________Electrical Submersible Pumps Fundamentals
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