1. Adjustable Speed Drives (ASD): Failure Reduction and Production Optimization
Notes go here.
Frank Ochoa
07/25/2007

2. 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.
I will discuss the ASD: it’s features and how it operates. We will then look at some of the wells that received the initial ASD’s, and see the results of having a drive on those wells. From those wells, we’ve determined the applications that we feel the drive is best suited for. We’ll also discuss the selection process for finding wells that fit into those applications. Finally, I will discuss the current results of ASD deployment and where we go from here.

3. Agenda Capabilities of the ASD Case Studies Applications of the ASD
Selection Process
Results and Projections

4. 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
Let’s talk about the difference between an ASD and a standard POC. When a POC detects pump-off, it shuts down for a set amount of time to let the well recover, then comes on and full speed until the next pump-off is detected. This process keeps repeating itself. When an ASD detects pump-off, it slows the well down, rather than shutting it off. It then monitors the well, and if it is recovering, it slowly increases the SPM until it either reaches a steady state, or it goes to pump-off again. This prevents the well from shutting down, which can have tremendous benefits.

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

6. 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.

7. Case Studies Wells Objectives Validate ASD Applications #43 Sec. 198
Develop Selection Criteria
Develop Standard Setup
Wells
#43 Sec. 198
#402 Sec.198

8. #408 Section 198
Job Reason Date Rod String Failure 9/15/2006 Rod String Failure 9/29/ Tubing Failure /29/ Rod String Failure 10/5/2002 Pump Failure /19/2000
Rotaflex Unit
20 BOPD, 700 BWPD
2 ¾” Big Bore Pump
SPM: Constant 4.3
288” Stroke Length
Hard Pump Off

9. Stroke per Minute Decrease
#43 Section 198
Job Failure
End Date
Rod String Failure
6/23/2006
Stroke per Minute Decrease
2/16/2006
2/9/2006
Tubing Failure
6/21/2005
1/22/2005
10/5/2004
Rod Pump Failure
3/14/2004
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
120 BOPD translates to $7200/Day using $60 Oil

10. ASD Applications Failure Rate Reduction New Well Stabilization
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
Three Phase power is required for higher-power applications. Transistorized inverter drives also allow the more-efficient three-phase motors to be used when only single-phase mains current is available.

11. 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
Loss of Coupling Displacement is when the rod string is pounding, the couplings loosen slightly on each pound. Over time this can cause the pins to break, or allow fluid to get into the couplings and cause damage through corrosion.

12. 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.

13. Eliminate Cycling Less starting/stopping of the Equipment
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.

14. 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

15. 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

16. 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

17. ASD Candidate Selection Process
New Wells
Rota-Flex Units above 3.5 SPM
ESP’s 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

18. 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

19. 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

20. Potential Benefits Potential Concerns Power Savings
Optimize Paraffin Treatment Schedule
Efficiency Increases
Nema B Motor v. “high-slip” Nema D Motor
Power Factor of .97
Slip is the difference in speed between the rotor and and the rotating stator magnetic field. The greater the slip, the slower the rotor speed, and the more torque developed by the motor.
Potential Harmonic Effect
Potential Concerns