Adjustable Speed Drives ASD: Failure Reduction and Production Optimization

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Adjustable Speed Drives (ASD) Failure
Reduction and Production Optimization

• Frank Ochoa
• 07/25/2007

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Introduction

• The Adjustable Speed Drive utilizes sensorless
  vector software to determine load and position.
  In a dynamic well environment, the ASD can seek
  the optimum Strokes Per Minute (SPM) to maintain
  a fluid level just above pump off, without
  shutting the well down. This results in a
  reduction of equipment loading, reduces failures,
  and maximizes fluid inflow to the wellbore.

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Agenda

• Capabilities of the ASD
• Case Studies
• Applications of the ASD
• Selection Process
• Results and Projections

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Capabilities of the ASD

• Continuously Adjusts Motor Speed to Match
  Productivity of the Well
• Intra-Stroke Speed Variation
• Slower Down-stroke
• Faster Upstroke
• Internal Pump Off Control or paired with Lufkin
  SAMS Controller
• Converts Single-phase Power to Three-phase
• Soft Start

• Drive Software
• Motor Torque is sensed and used to control the
  drive

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ASD Provider

• Lufkin ASD
• Crane, TX
• Original Drive Tested
• Cutler Hammer SVX-9000
• Current Drive
• Toshiba
• Software
• SALT Sensorless Artificial Lift Technology

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Vendor Stated ASD Lift Applications

• Conventional Pumping Units
• Most common artificial lift unit.
• Rotaflex Units
• A Rotaflex is an ultra long stroke pumping unit
  that is used primarily for deep high-volume
  wells. Fills a niche between conventional and ESP
  units.

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Case Studies

• Objectives
• Validate ASD Applications
• Develop Selection Criteria
• Develop Standard Setup

• Wells
• 43 Sec. 198
• 402 Sec.198

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408 Section 198

• Job Reason Date Rod String
  Failure 9/15/2006 Rod String Failure 9/29/2003
  Tubing Failure 8/29/2003
  Rod String Failure 10/5/2002 Pump Failure
  4/19/2000

• Rotaflex Unit
• 20 BOPD, 700 BWPD
• 2 ¾ Big Bore Pump
• SPM Constant 4.3
• 288 Stroke Length
• Hard Pump Off

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43 Section 198

• Conventional 640 Pump Unit
• 120 BOPD, 200 BWPD
• 2 ¾ LB Pump
• SPM Constant 8.6
• 168 Stroke Length
• High Cycle Rate

• 3 Failures in 12 Months

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ASD Applications

• Failure Rate Reduction
• Eliminate Fluid Pound
• Reduce Rod Buckling
• Reduce or Eliminate Cycling
• Conventional, ESP, and Rota-flex
• Smooth Upstroke/Downstroke Transition
• Reduce Motor Temperature
• New Well Stabilization
• Rota-flex Optimization

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Eliminate Fluid Pound

• Fluid pound is caused by Incomplete Pump Fillage.
  
• It can lead to
• Shock Wave
• Gearbox Wear
• Loss of Coupling Displacement
• Equipment Failure
• Rod Fatigue
• Rod Wear
• Tubing Wear
• Pump Component Failure

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Reduce Rod Buckling

• Rod Buckling is the primary cause of tubing and
  rod wear failures. Rod buckling can be caused by
• Fluid Pound
• Downstroke Compressive Forces
• Sucker Rod Velocity
• Crooked Hole
• Pump Sticking
• The ASD can reduce rod buckling by
• Maintaining a fluid level above pump-off so that
  fluid pound does not occur.
• Slowing the downstroke while speeding up the
  upstroke to minimize compression.

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Eliminate Cycling

• When the ASD detects pump-off, it slows the pump
  down instead of shutting it off. This allows the
  well to recover while maintaining fluid flow into
  the pump. This is advantageous for many reasons
• Less starting/stopping of the Equipment
• Solids Control
• Continuous fluid flow eliminates sand, iron
  sulfide, etc. from falling back onto the pump.
• Continuous fluid flow reduces scale, paraffin and
  asphaltine buildup.

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Upstroke/Down-stroke Transition

• Slower transitions reduce loads and stresses on
  both surface and down-hole equipment
• Applicable to Conventional Units
• Will be tested on Lufkin Mark Unit

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New Well Stabilization

• Match changing well production
• Keeps solids moving during cleanup
• Compensate for minor design inefficiencies
• Maximize inflow by maintaining minimum fluid
  level in the wellbore

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Rota-Flex Optimization

• The ASD can optimize these units by
• Upstroke/Down-stroke Speed Variation
• Transition Load Reduction
• This translates into
• Less Failures
• Less Wear on Equipment
• Longer Runtime
• Rota-Flex Unit
• Down-hole Equipment

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ASD Candidate Selection Process

• New Wells
• Rota-Flex Units above 3.5 SPM
• ESPs that cycle due to fluctuating production
• High Failure Rate Wells meeting certain Criteria
• We identify wells listed with 2 or more failures
  in the last 12 months.
• WellServ
• Lowis
• Catalyst
• We then sort the wells based on failure mode and
  operating conditions that the ASD could effect.
• Rod and Tubing Wear, Pump Failures
• SPM, Runtime, Stroke Length
• Meet with Artificial Lift/Corrosion Rep for final
  review and candidate selection

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ASD Selection Process

• Reviewed Rota-flex SPM
• Repeat Failure Candidates
• 9 of wells account for 51 of failures
• Wells sorted by failure type
• Reviewed with Artificial Lift Rep
• Submit Recommended Wells

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Results and Projections

• Adjustable Speed Drives have a definite benefit
  in the oilfield. When placed in the correct
  application, the ASD can
• Reduce Failures
• Optimize Production
• Reduce Equipment Changes
• Reduce Operating Expenses
• Reduce Downtime
• Fast Payout

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Potential Benefits

• Power Savings
• Optimize Paraffin Treatment Schedule
• Efficiency Increases
• Nema B Motor v. high-slip Nema D Motor
• Power Factor of .97

Potential Concerns

• Potential Harmonic Effect