Update on ELift

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Update on ELiftSAGD artificial lift

• Presentation to
• Artificial Lift Low-Pressure SAGD Subcommittees
• Nov 2004
• Ken Kisman Ph.D., P.Eng.

www.rangewest.ca
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Update on ELift

• Since my last presentation to the Artificial Lift
  Subcommittee on June 17, 2003
• An artificial lift paper was published in JCPT,
  August 2003
• A presentation was made to the 2004 Slugging it
  Out conference which is available at
  www.petsoc.org/SIO_2004/Kisman.pdf

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Low-pressure SAGD summary

• Advantages (even in absence of thief zones)
• Reduced heat requirements
• Reduced emissions (Kyoto)
• Less source water needed
• Less facilities for steam generation water
  treatment
• Lower capital cost for piping vessels
• Improved operations (reduced H2S, CO2, silica,
  scaling, may eliminate sulphur plant)
• Disadvantages
• Drilling of more well pairs initially although
  total number needed is approx. the same (or less)
• Artificial lift may add extra cost (or reduce
  costs when surface fluid separators not needed)

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Subcool Issues

• Examples of Low-Pressure Challenges
• Flashing to steam is triggered by a much smaller
  ?P in the liner up to the pump (eg 59 kPa
  versus 230 kPa)
• Flowing bitumen viscosity is much higher (eg 61
  cp versus 9 cp)
• Higher mixed subcool for a given liquid head over
  a pump
• Bitumen rates per well are lower so it is more
  important to optimize operations
• Low subcool (ie vigorous lift) is particularly
  important at low pressure
• (for more details, see 2004 Slugging it Out
  presentation)

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

• .

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The next major SAGD advance

• The only way to be sure that bitumen rate, SOR,
  recovery factor, emissions water use are
  optimized is
• Use low-pressure SAGD
• Use vigorous lift, with low subcool values, for
  extended periods

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Concentric ELift configuration
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Concentric ELiftchanges from parallel operation

• Concentric inner outer tubing are installed
  instead of parallel tubing strings
• The outer tubing is insulated (substantially from
  the base to the port)
• 1st stage flow up to the port is between the
  outer tubing and the casing
• The liquid pool flowing down to the pump is
  between the inner and outer tubing.
• 2nd stage flow to the surface is up the inner
  tubing.
• (parallel ELift operation is described in JCPT
  paper August 2003)

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Advantages of Concentric ELift over Parallel
ELift

1. Can be installed in 9 5/8 intermediate casing
2. Both configurations provide good performance at
   moderate flow rates but concentric ELift allows
   higher flow rates because flow area in 1st stage
   can readily be larger
3. Concentric option allows simpler wellhead, easier
   installation of tubulars, more room for a pump
   motor
4. There is very little pressure drop across the
   packer

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Concentric ELift simulation

• The QFlow thermal wellbore simulator has been
  modified to allow SAGD simulation with concentric
  ELift as well as parallel ELift
• Mike McCormack
• Fractical Solutions Inc

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Concentric ELift simulation example 1 with QFlow
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Concentric ELift simulation example 2 with QFlow
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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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A downhole motor adds heat to fluids prior to
pump intake

• Standard single-stage pump configuration
• A downhole motor adds heat to the fluids prior to
  the pump intake and increases flashing
• ELift shroud option for motor
• A shroud around the motor may be used so flow of
  the liquid pool cools the motor. This will cause
  the same heating of the pumped fluids but the
  high pump subcool provided by ELift will prevent
  flashing
• Optionally insulate the section of 2nd stage
  tubing from the pump to the elevation of the
  port.
• Note the shroud benefits from liquid-only flow

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ELift option can prevent heating of pumped
fluids by a downhole motor

• 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.
• Optionally, a heat transfer fluid can be used
  around the motor at base of tubing for increased
  thermal conduction to the outer tubing
• eg commercial heat transfer fluids or liquid
  fusible alloys
• Simulations show that the subcool at the pump
  inlet is almost unchanged by the use of the
  downhole motor. Hence, the full subcool benefit
  provided by ELift is maintained even with a
  downhole motor

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Concentric ELift Simplest instrumentation
configuration

• Pressure in liquid pool
• An electronic pressure sensor string (attached to
  the pump cable) is landed above the pump. This
  enables control of the liquid level (by
  controlling the gas production rate at the
  surface)
• Liner temperature
• A thermocouple string (attached to the pump
  cable) extends below the downhole motor to
  measure bottomhole heel temperature for
  (indirect) subcool measurement control

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Current ELift royalty rate

• 800 per well-pair per month

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Artificial lift field pilot

• Need to demonstrate the following
• COMBINATION of
• Low steam chamber pressures
• Low mixed subcool
• Long pump service life

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Main overall ELift advantages

• Improved recovery performance due to vigorous
  lift with low subcool in liner
• Choice of pumps the pumps have longer service
  life
• Good downhole gas-liquid separation in each well