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SAGD ELift Applications

Canadian Artificial Lift School

November 2006

Ken Kisman Ph.D., P.Eng.

www.rangewest.ca

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Low-pressure SAGD with artificial lift:Reasons

(A) Thief ZonesUpper gas & water sand thief zones and/or

bottom water are common in the Athabasca deposit

(B) SAGD Wind-down Requires low pressure and/or injection of non-

condensable gas

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Low-Pressure SAGD with artificial lift: Reasons

(C) Improved SOR & economics Less natural gas required Less facilities for steam generation & water treatment Lower capital cost for piping & vessels

(D) Environmental benefits Reduced emissions (Kyoto) Less source water needed

(E) Improved operations Reduced H2S, CO2, silica, scaling, & may eliminate

sulphur plant

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Low-Pressure SAGD with artificial lift: Reasons

(F) More oil from same plant

Example Plant Oil

SOR Production

High pressure: 2.5 30,000 b/d Low pressure: 1.9 40,000 b/d

• with relatively modest extra facilities• addition of artificial lift• drilling of more well pairs initially (although total

number needed is approx. the same)

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SAGD artificial lift completionrequires production tubing to toe

Bottomhole pump

Production tubing to toe

Packer

(to maintain full length of well hot & maximize steam chamber development all along the well pair)

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SAGD steam-trap controlDefinition of subcool

SAGD injection well

SAGD production well

“Subcool” is the difference between the measured temperature at a location and the saturated steam temperature at that location

Saturated steam temperature is calculated from the measured pressure at that location using steam tables

“Low” subcool is close to 0 °C typical ranges 0 – 5 °C or 0 – 10 °C

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Reference “mixed subcool” & additional potential subcool locations

Local Subcool Pump Subcool Mixed Subcool

Inter-well Subcool

Steam Cham- ber

Chamber-Well Subcool

Steam Cham- ber

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Cartoon of Local & Mixed Subcool Values Along a SAGD Horizontal Well

Low mixed subcool requires lifting harder &

increases the oil production rate

Local subcoolMixed subcool

Low mixed subcool minimizes the local subcools, maximizes height of steam

chamber & maximizes steam chamber development along the well pair

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Low Subcool

Low subcool (ie vigorous lift) is particularly important at low pressure

Low subcool is more important for lower quality reservoirs

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Cartoon showing how low subcool might increase steam chamber development along a well pair

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High mixed subcool

Low mixed subcool

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Evidence of need for low subcool values

SAGD Field Projects

UTF pilot Phase B used subcool values close to 0 °C in the production liner

Surmont pilot reported much higher oil rates & improved SOR with low subcool (EUB Resource Management Reports)

Simulations with real-life conditions Kisman JCPT Aug 2003

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Low Pressure Challenge:Saturated steam conditions reached prior to pump inlet

for a standard pump configuration

Volume increases 600 fold when water flashes to steam

200 kPa ∆P typical along production tubing

∆P of only 59 kPa will initiate flashing to steam

100 kPa ∆P due to hydraulic head up to pump inlet

A downhole motor adds heat to the fluids

800 kPaa steam chamber 200 kPa drawdown 4 °C subcool

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Examples of low-pressure challenges: (a) 1000 kPaa versus (b) 3500 kPaa

∆P required to reach saturated steam conditions (a) 59 kPa (b) 230 kPa

Steam Chamber

Bitumen Viscosity (a) 61 cp (b) 9 cp

Steam Cham-ber

Volume of steam from flashing is much greater at lower pressure

At low pressure, bitumen rates are lower so it is more important to optimize operations

A given liquid head over a pump means higher mixed subcool

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Steam chamber may reach pump

due to axial growth or from another well pair

Steam chamber has reached location of pump --- adding heat to fluids

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SAGD Artificial Lift Standard Bottomhole Pump Configuration

Average liquid head required must be determined empirically

High liquid head Average liquid head over pump must be higher than NPSH due to unstable fluid production

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SAGD Artificial Lift Standard Bottomhole Pump Configuration

Difficult Conditions1) High temperature fluids 2) Saturated steam conditions with flashing to steam

and gas breakout3) High lift rates required to achieve low subcool

values in the production liner 4) Scaling in pump5) Unstable flow

slugging between bitumen & water inflow rates varying with time

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What if available artificial lift cannot lift hard enough to provide low mixed subcool?

Some bitumen recovery will still be obtained but only part of the well may have a steam chamber

There is no way of knowing how much better the bitumen rate, SOR, & recovery factor would be with low mixed subcool

The only way to be sure that field performance is optimized is to use vigorous lift, with low subcool values, for extended periods

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Current SAGD lift status

Some SAGD operators are:

satisfied that electrical submersible pumps (ESPs) are providing adequate lift

expecting improving run life for ESPs

not unduly concerned about subcool and reservoir performance issues.

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A fully successful SAGD lift system

To be fully successful, a SAGD lift system must demonstrate the following

Combination: Low steam chamber pressures Low mixed subcool Long service life

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ELift™: a patented 2-stage lift system Concentric configuration

Liquid pool in inner (tubing) annulus

2nd stage upper production tubing

Port

Gas prod-uction

Insulated tubing

Optional downhole motor

Inlet to 2nd stage bottomhole pump

Top of 1st stage in outer (casing) annulus

Liquid production

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Summary of ELift features

Port

Gas prod-uction

Liquid production

Low subcool & improved recovery

Pump has longer service life

Conditioning of fluids prior to pump intake:

(a) High pump subcool Elimination of flashing to steam Reduced scaling in pump

(b) Lower temperature (c) Higher intake pressure (d) Elimination of non-condensable gas (e) Buffered, more stable flow at pump

Good liquid-gas downhole separation in each well

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Concentric ELift Simplest instrumentation configuration

Port

Gas prod-uction

Liquid production

Liner temperature

A thermocouple string (attached to the pump cable) extends below the downhole motor to measure bottomhole heel temperature

Pressure in liquid pool

An electronic pressure sensor string (attached to the pump cable) is landed above the pump

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ELift control functions

Port

Gas prod-uction

Liquid production

(B) Steam trap control

Vary liquid production rate at surface to control the subcool value measured in the liner (at toe or at heel)

(A) Liquid level control at elevation of port

Vary gas production rate at surface to control the ∆P between sensor in liquid pool and surface pressure

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Cooling of motor when downhole motor is used

(A) ELift shroud option for motor

A shroud around the motor may be used so flow of the liquid pool cools the motor. There is only liquid flow in the shroud. The high pump subcool provided by ELift will prevent flashing

(B) ELift 1st Stage Cooling Option for Motor

Motor does not have a shroud. A section of outer tubing at the elevation of the motor is left uninsulated so the motor is cooled by concentric flow up the 1st stage.

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Concentric ELift tubing sizes

Example configurations

Casing

od

Insulated outer tubing

od (id)

Inner tubing

od

9 5/8” 7 5/8” (~6.0”) 2 7/8”

9 5/8” 7 ¾” (~6.5”) 2 7/8”

11 ¾” 9 5/8” (~8.0”) 3 ½”

13 3/8” 10 ¾” (~9.0”) 4 ½”

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ELift simulation

ELift performance can be predicted with the QFlow** thermal wellbore simulator

** Mike McCormack

Fractical Solutions Inc

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ELift concentric QFlow simulation example CALS 1

► low subcool in liner ► conditioning of fluids at the pump inlet

Port

Gas prod-uction

Elevation of pump above liner 1 mTVD Elevation of port above liner 100 mTVD Depth of liner at least 100+30=130 mTVD

Intermediate casing 13 3/8” OD

Insulated “tubing” 10 ¾” OD, 8.94” ID

Water rate = 800 m3/d Oil rate = 400 m3/d

Pump

P = 1185 kPaa T = 133 °C Subcool at pump inlet = 55 °C

P = 297 kPaa T = 133 °C Steam quality = 10.4 %

P = 900 kPaa T = 175 °C Subcool at heel = 1 °C

Liquid production

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ELift concentric QFlow simulation example CALS 2 ► low subcool in liner ► conditioning of fluids at the pump inlet

Port

Gas prod-uction

Liquid production

P = 414 kPaa T = 146 °C Steam quality = 7.8 %

Elevation of pump above liner 1 mTVD Elevation of port above liner 60 mTVD Depth of liner at least 60+30=90 mTVD

Intermediate casing 9 5/8” OD

Insulated “tubing” 7 ¾” OD, 6.28” ID

Water rate = 400 m3/d Oil rate = 200 m3/d

Pump

P = 926 kPaa T = 146 °C Subcool at pump inlet = 31 °C

P = 900 kPaa T = 175 °C Subcool at heel = 1 °C

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ELift parallel configuration

Top of 1st stage

Casing annulus

Second stage production tubing

Packer

Port

Completion interval

First stage production tubing

Liquid production

Gas prod-uction

Liner annulus

Insulated tubing

Inlet to 2nd stage with gas lift or bottomhole pump

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ELift parallel QFlow simulation example CALS 3

P = 800 kPaa T = 168 °C Subcool = 2 °C Water Rate = 300 m3/d Oil Rate = 150 m3/d

P = 706 kPaa T = 165 °C Steam present: quality = 1.8 %

P = 1607 kPaa T = 116 °C Subcool = 85 °C

P = 226 kPaa T = 124 °C Steam quality = 11.7%

Steam Chamber Pressure = 1000 kPaa

Liquid production

Depth of liner = 360 m Total measured well length = 1400 m Length of completed interval = 700 m Elevation of pump above liner = 10 m TVD Elevation of port above liner = 160 m TVD

Gas prod-uction

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Choice of Concentric ELift or Parallel ELift

(a) Concentric can be installed in small 9 5/8” od intermediate casing

» for low or moderate flow rates» careful design required

(b) For large intermediate casing, both concentric and parallel configurations should be considered

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ELift benefits: (a) Subcool & Recovery

ELift uses natural lift in 1st stage to an intermediate elevation

Provides vigorous lift with low mixed subcool at low bottomhole pressures

Provides substantial recovery, facility & environmental benefits due to low pressure SAGD with low subcool

Increased feasibility for development of lower quality reservoirs (which require optimization)

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ELift benefits: (b) Pump

Potential to reduce pump costs by half orbetter

Can use standard, less expensive pumps

Increased pump life Supported by indirect field evidence

Whatever improvements are made over time to pumps, pump life should always be longer when the pump is used with ELift because of fluid conditioning by ELift

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ELift benefits: (c) ELift isolates the steam chamber during pump changes

Bridge Plug

Port

Pump

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ELift benefits: (d) downhole gas/liquid separation

Complete downhole gas/liquid separation provided by ELift

Eliminates the need for surface multiphase group separators

Allows good measurement of liquid production rates for each well & hence allows optimization of each well pair

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ELift field demonstration

Parallel ELift, with gas lift in 2nd stage, wasused for 3 years in ConocoPhillip’s Surmont

SAGD pilot Main principles of ELift were demonstrated

Very low mixed subcool values were obtained

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Artificial lift field pilot

New piloting is needed to demonstrate the following: COMBINATION:

Low steam chamber pressures Low mixed subcool Long pump service life

Note that pump performance when used at high pressures does not translate down to low pressures since all aspects are more challenging at low pressures

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Recommendation:Use Large Intermediate Casing

in future SAGD production wells

Facilitates the option of 2-stage ELift artificial liftOtherwise, future operations could be jeopardized

if low pressure becomes necessary

Typical extra well drilling cost is modest for 13 3/8” casing

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Main Conclusionsre: SAGD artificial lift with ELift

1) Any current or future SAGD pump should work better with ELift

2) The benefit could be substantial even if the only benefit considered is either

Increased pump life, or

Isolation of the steam chamber during pump changes etc

3) Optimization with ELift is particularly important for lower quality reservoirs

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Main Conclusions SAGD artificial lift with ELift

has benefits under five main headings

(a) Improved recovery performance

due to vigorous lift with low subcool in liner

(b) Pump savings less expensive pumps & longer pump life

(c) Isolates steam chamber during workovers

(d) Good downhole gas-liquid separation

(e) Makes low-pressure SAGD more feasible Economic, environmental, operations benefits