SAGD ELift Applications

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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 liftReasons

• (A) Thief Zones
• Upper 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
(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
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Reference mixed subcool additional potential
subcool locations
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Cartoon of Local Mixed Subcool Values Along a
SAGD Horizontal Well

Local subcool
Mixed subcool
Low mixed subcool minimizes the local subcools,
maximizes height of steam chamber maximizes
steam chamber development along the well pair
Low mixed subcool requires lifting harder
increases the oil production rate
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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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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 ChallengeSaturated steam
conditions reached prior to pump inlet for a
standard pump configuration
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Examples of low-pressure challenges (a) 1000
kPaa versus (b) 3500 kPaa
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Steam chamber may reach pump due to axial growth
or from another well pair
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SAGD Artificial Lift Standard Bottomhole Pump
Configuration
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SAGD Artificial Lift Standard Bottomhole Pump
Configuration

• Difficult Conditions
• High temperature fluids
• Saturated steam conditions with flashing to steam
  and gas breakout
• High lift rates required to achieve low subcool
  values in the production liner
• Scaling in pump
• 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
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Summary of ELift features
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Concentric ELift Simplest instrumentation
configuration
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ELift control functions
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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
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ELift concentric QFlow simulation example CALS 2
? low subcool in liner ?
conditioning of fluids at the pump inlet
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ELift parallel configuration
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ELift parallel QFlow simulation example CALS 3
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Choice of Concentric ELift or Parallel ELift

• Concentric can be installed in small 9 5/8 od
  intermediate casing
• for low or moderate flow rates
• careful design required
• 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 or
• better
• 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
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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, was
• used for 3 years in ConocoPhillips 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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RecommendationUse Large Intermediate Casingin
future SAGD production wells

• Facilitates the option of 2-stage ELift
  artificial lift
• Otherwise, 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

• Any current or future SAGD pump should work
  better with ELift
• 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
• 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

• Improved recovery performance
• due to vigorous lift with low subcool in liner
• Pump savings
• less expensive pumps longer pump life
• Isolates steam chamber during workovers
• Good downhole gas-liquid separation
• Makes low-pressure SAGD more feasible
• Economic, environmental, operations benefits