Variable frequency drives rod pump control podcast
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Transcript of Variable frequency drives rod pump control podcast
Introduction to Variable Frequency Drives and Rod Pump ControlFreddy Jones, Manager – Offer Development
Variable Frequency Drives Overview
Variable Frequency Drives Overview
By 2050, demand for energy will have doubled, but CO2 emissions must be cut in half!
Variable Frequency Drives Overview
Industrial Chiller UnitCooling Tower Fans
Industrial Pumps
Variable Frequency Drives Overview…with another 15% devoted to material handling applications
Baggage Handlers
Cranes/Hoists
Conveyors
Variable Frequency Drives Overview• The vast majority of these instances offer very little control other than:
– Turn it on
– Run it at full speed
– Turn it off
Square D Motor Starter
Variable Frequency Drives Overview•Running motors this way is very inefficient and contributes to increased wear and tear on both the motors and the components that they power
– Starting and stopping motors by using across-the-line contactors can cause undesirable consequences•Inrush current of 8X normal
•Overheating
•Undue stress on shafts, pulleys, belts
•Harmonics created by numerous simultaneously starting motors
•Interference transmitted back through systemHigh Inrush Current at Motor Startup
– The output required of a system can change over a period of time
•HVAC systems don’t need to run at full speed both day and night
•Pump flow rates need to change at various times throughout the process
Variable Frequency Drives Overview• Starting, stopping and throttling motors requires human intervention
– Timers can be installed, but they don’t solve the starting problem, and they still only provide on/off control
– Soft or reduced-voltage starters can be used, but they can only ramp up to (or slow down from) full speed
– Flow control is traditionally done by restricting the medium in some way using valves or dampers
Variable Frequency Drives Overview• Many material handling applications require controlled starting and
stopping either when automated or under human control
– Overhead crane applications where swinging and swaying effects need to be dampened
– Conveyors and moving equipment where products might be sensitive to breakage due to backlash during acceleration and deceleration
Variable Frequency Drives Overview• The Variable Frequency Drive (or VFD) offers ways to manage these
issues
– Schneider Electric offers a complete range of Altivar® VFDs for any application
Load
Better power factor, reduced harmonic distortion, lower
sensitivity to incoming phase sequencing
Variable Frequency Drives Overview
Incoming three phase power
Using Variable Frequency Drives
• When connected to an AC motor, the drive delivers controlled power to the motor at constant V/Hz ratio…
Pulse Modulated Output
Rectifier converts incoming power to DC, then inverter converts back to
controlled pulse AC
Variable Frequency Drives Overview
Using Variable Frequency Drives
• The primary benefit of using VFDs is energy efficiency
– Power consumption by a VFD as a function of speed is considerably lower than a motor alone, especially when run at less than full speed
% Power Consumed
% Flow
Example: Desired flow rate is 80%
Using VFD to slow motor (rather than running motor at full speed and using valves) saves up to 50% of power consumed
Simple Pump Application
Flow control with VFD vs. valves or dampers
Variable Frequency Drives OverviewClick “Energy Savings Calculator” below for web-based demo…
Variable Frequency Drives Overview
Two primary types of VFDs
• Variable Torque
– Found in applications where torque increases as a function of speed
– Primarily centrifugal pumps and fans
– The faster you run these applications, the torque (and hence the power) required to do so increases exponentially
• Constant Torque
– Torque only changes directly proportional to speed
– Constant torque applications include mixers, compressors, conveyors
Variable Frequency Drives Overview
Using Variable Frequency Drives
• The VFD is programmable for managing the entire process
– Can be programmed to ramp up slowly and smoothly at start up, thus reducing high starting torque and current surges
– VFDs can maintain motor speed at values less than full speed, enabling considerable energy savings over motors alone
– VFDs can speed up, slow down, stop, restart, and vary torque over the course of time, allowing for complete automation of the process over a day, a week, or more
– VFDs offer the added feature of acting as phase converters, converting single phase input power into three phase output, a situation often encountered in remote locations such as field irrigation or pumpjack sites
LOAD
Variable Frequency Drives Overview
Three phase power in
Using a PLC to control drive
Feedback from load source
PLC issues commands to the drive
Drive controls the
load
LOAD
Variable Frequency Drives Overview
Three phase power in
The ATV 61 & 71 with Integrated Machine Controller (IMC) Card
Feedback from load source
Drive controls the
load
Integrated controller card mounts right into the drive
External PLC is eliminated
Refresher: “Pumpjack: 101”
Pump Jack Operation:
“Artificial lift” system extracts oil from a reservoir using a reciprocating rod with a valve mechanism at the bottom
Rod Pump (Pump Jack) Refresher
Oil Production Issues:1. Maximizing productivity
2. Maintenance and downtime costs caused by equipment wear
3. Access to remote equipment
4. Reducing energy costs
Beam
Bridle
Stuffing Box
Crank Arm and Counter Weights
Polished Rod
Basic Pump Jack ComponentsBasic Pump Jack Components
Drive Enclosure
Pump (underground)
“Horse” or “Donkey” head
Motor – traditionally
NEMA D, but often NEMA B when used with VSD
Gearbox
Belt Guard
Ground/surfaceGround/surface
Fluid/Oil
Perforations
Standing valve shut
Downstroke
Traveling valve open
Downward motion of plunger causes standing valve to close and traveling valve to open – fluid flows up through plunger.
Tubing
Casing
Stuffing Box
Upstroke
Standing valve open…creating negative pressure in barrel, which opens the standing valve and more fluid flows in.
Traveling valve shut
With traveling valve now shut, plunger lifts column of fluid upward as it rises…
Fluid exits stuffing box by pipe
If pumping at correct speed, fluid level is
maintained.
Anchors
Pump Jack Issues and Problems: Why Avoid Over-pumping?
Fluid Pound• Occurs when plunger hits the
fluid on the down stroke
• Worst case is when pump fill <=50%
• Rod string compresses, twists, and may eventually break
• Plunger “hammers” the fluid
• Production loss
Ground/surface
Desired fluid level
Plunger direction
Full weight of fluid column is still in plunger as it begins downstroke.
Fluid does not fill barrel
completely, leaving a gap.
Pump Jack Issues and Problems: Why Avoid Over-pumping?
Fluid Pound• Occurs when plunger hits the
fluid on the down stroke
• Worst case is when pump fill <=50%
• Rod string compresses, twists, and may eventually break
• Plunger “hammers” the fluid
• Production loss
Ground/surface
Desired fluid level
Plunger direction
Lack of fluid in barrel means traveling valve doesn’t open until it hits the fluid, creating a pounding effect.
Gas Compression (Gas Lock)• Results from very low pump fill
• On the down stroke, the standing valve is closed; the travelling valve also remains closed. The gas is compressed
• On the up stroke, the gas expands but both valves remain closed
• The plunger travels up and down without pumping oil. This results in energy waste, production loss, and mechanical wear as the plunger is no longer lubricated
Pump Jack Issues and Problems: Why Avoid Over-pumping?
Ground/surface
Level is so low that plunger movement does not draw fluid through the standing valve.
Plunger direction
Desired fluid level
Gas Compression (Gas Lock)• Results from very low pump fill
• On the down stroke, the standing valve is closed; the travelling valve also remains closed - the gas is compressed
• On the up stroke, the gas expands but both valves remain closed
• The plunger travels up and down without pumping oil. This results in energy waste, production loss, and mechanical wear as the plunger is no longer lubricated
Pump Jack Issues and Problems: Why Avoid Over-pumping?
Ground/surface
Plunger direction
Neither valve opens as the plunger travels up & down, allowing a gas pocket to form in the barrel.
Desired fluid level
Result of equipment damage…
Pump Jack Issues & Problems: Over-pumping Consequences
Pulling the rod string is very expensive - not only due to
labor and equipment, but lost production costs can run into
tens of thousands of dollars
The damaged rod string must be pulled from the well for repairs
Why is Pump-Off Control important?
●How does the pump operator get the most production from his well without over-pumping and risking equipment damage?
● Pump too little and you don’t get maximum production
● Pump too much and you create a “pump-off” condition (no fluid in the well barrel), harming the equipment
●Rod Pumps have historically been run with across the line contactors, the pump regulated by periodically turning off the motor
● Starting and stopping was initially done by hand
● The use of timers meant this could be done “automatically” without having to be present at the well site
● How long to allow pump to sit idle before restarting? Best guess? Trial and error?
Why is Pump-Off Control important?
●Using a VFD, with its ability to act as a timer and a soft starter allows the pump operator to accomplish the same thing, plus some benefits:
● Less wear and tear on the motor than across the line starters
● Ability to run at speeds less than maximum, allowing for reduced energy consumption
● Smoother input current and ability to operate using single-phase power.
● Significant problem still remains:● Pumper still doesn’t know how long to
let pump sit idle between runs● Limited ability to react to unexpected
changes in the well● No further insight as to what is actually
happening deep down in the well
How to Address the Problem? The Schneider Electric ATV71 drive with Integrated Machine Controller (IMC) card acts as a drive and a PLC-in-one to control the well in real time based on well conditions…
Fully Automated Pump-Off Control Options
● Basic: Torque-Only Control: ● Uses motor torque measured by the drive to
monitor the load on the rod string to control pump operation
● Cost effective solution for wells of 1500m or less● Think: “entry level” solution (there are a lot of
these in the market) ● Still not the most accurate picture of what’s
happening (uses no load cell)
● Advanced: Dynamometer Card Control: ● Load cell measures forces acting on the rod
string; controller uses this data to manage pump operation
● Creates an x-y plot, providing ultimate optimization using well data and visual system tuning
● Downhole control uses an advanced algorithm to determine rod load at the bottom of the well
So, just what is a dynamometer card?
Bottom of Stroke
Load Cell collects data as rod string moves up and down…
Understanding the Dynamometer Card
Displacement (up and down)
Lo
ad …and the data is
plotted onto the graph
Ground/Surface
Stuffing Box
Dynamometer Displays: Using Load Cell and Pump Position Data
Plot of load vs. position at the load cell for one complete cycle (up-and-down stroke) actually looks like this - called a “surface” card
Displacement
Lo
ad
The same data, after correcting for rod stretching, flexing, and
stress wave propagation, looks like this, giving a clear view of
what’s happening at the bottom of the well (“downhole” card)
Displacement
Lo
ad
Displacement
Lo
ad
A
Diagnostics with Downhole Dynamometer Card
Bottom of Stroke: Beam is at lowest point; load and displacement are at point “A”
A Bottom of Stroke
Load Cell
Minimum Load
Minimum Displacement
Displacement
Lo
ad
A
Bottom of Stroke: The instant torque is applied to the beam, the traveling valve shuts and load increases to point “B”
B
A, B Bottom of Stroke
Diagnostics with Downhole Dynamometer Card
“Load” consists of the weight of the fluid + the weight of the rod string as measured by the load cell
Maximum Load
Minimum Displacement
Displacement
Lo
ad
A
Top of Stroke: As the beam moves upward, load remains constant as displacement increases to point “C”
B
Bottom of Stroke
C
A, B
CTop of Stroke
Diagnostics with Downhole Dynamometer Card
UpstrokeMaximum Load
Maximum Displacement
Displacement
Lo
ad
A
Top of Stroke: Torque is reversed and load drops back to point “D”
B C
A, B
C, D
D
Top of Stroke
Bottom of Stroke
Diagnostics with Downhole Dynamometer Card
Fluid is released (traveling valve is open), so plunger can move freely back down the barrel
Maximum Displacement
Minimum Load
Bottom of Stroke: Load and displacement return to point “A”
Bottom of Stroke
Displacement
Lo
ad
A
B C
D
Top of Stroke
Diagnostics with Downhole Dynamometer Card
A, B
C, D
DownstrokeMinimum Load
Minimum Displacement
Optimizing Well Performance“Ideal” Downhole Dynamometer Card
• Indicates rod load at the BOTTOM of the well versus rotation at top
•The “ideal card” is a fully optimized system in terms of production and equipment operation
A – C = Upstroke
C – A = Downstroke
Ground/surface
Plunger direction
Diagnostics with Downhole Dynamometer Card – Fluid Pound
Lo
ad
Displacement
Traveling valve still closed as downstroke begins
A
B C
D
Ground/surface
Plunger direction
Diagnostics with Downhole Dynamometer Card – Fluid Pound
Lo
ad
Displacement
Sudden impact with fluid rapidly opens valve
A
B C
D’
Wasted Motion/ No Production
Plunger only fills from D’ to A
D
Diagnostics with Downhole Dynamometer Card●Provides significant information about the well and its performance
●Identifies issues limiting production and damaging equipment
●Our solution uses the dynamometer card from each pump stroke to constantly optimize performance, even under changing conditions
Diagnostics with Downhole Dynamometer Card
A couple of examples…
Unanchored Tubing
Position
Force Pump and tubing moving together; force can not reach maximum until tubing movement/stretching stops.
Pump and tubing move together on downstroke. A portion of potential pump fill is lost.
Pump Tapping (top or bottom)
Force
Position
Plunger hits top of pump while on upstroke; results in a spike in the force reading
Plunger hitting bottom momentarily causes a drop in force on the rod string
Diagnostics with Downhole Dynamometer Card
0Actual Oilfield Data, Perryton, TX
Diagnostics with Downhole Dynamometer Card – Effective Stroke and the RPC
Lo
ad
Displacement
Total Stroke
Max Load
Min Load
Fill Status = Effective Stroke/Total Stroke
A
B C
Downstroke
D
Effective Stroke
D’
In this situation, Fill is only about 55%
From B to C, pump is lifting
From D to A, pump is refilling
Upstroke
Basic system response is largely governed by a calculated value for Fill Status• Fill Status = an estimate of % pump fillage for each stroke of the pumpjack as
calculated by the RPC algorithm
Fill Target vs. Fill Minimum
• Fill Status, relative to Fill Target - determines whether the system increases or decreases speed (RPC system changes speed as often as the user-determined “Speed Change Strokes” setting allows)
• Fill Status, relative to Fill Minimum - determines when the system enters Pump Off status (RPC system enters Pump Off when “Pump Off Count Limit” is reached, and remains off for user-determined period of time)
Diagnostics with Downhole Dynamometer Card – Fill Status
Ground/surface
Tying it all together…
Keeping it in the “sweet spot”• By monitoring the load on the rod
string, the Rod Pump Controller continually adjusts the speed of the pumpjack so the pump operates in its “sweet spot” – the point where the pump is lifting a full load of fluid with each stroke, while not allowing the fluid inside the casing to drop below the desired level
• This is Rod Pump Optimization!
• The Downhole Solution provides both Control and Diagnostics
The Schneider Electric RPCComponents and Installation
3. Complete RPC Drive Cabinet
Schneider Electric Rod Pump Controller
1. Rod Pump Controller Kit - upgrade an existing ATV71 drive
Three Options for the Customer:
2. RPC Panel Builder Bundle – Includes kit and drive only
Schneider Electric Rod Pump Controller Kit● Integrated Machine Controller
Card (IMC) for Altivar 71 Drive● Rod Pump Control algorithm
loaded on IMC
● Proximity Sensor with required cables and mounting hardware, brackets & magnets
● Relays – (2) Run Interrupt and optional Start Warning Indicator
● Load Cell with required cables and hardware (Downhole only)
● Instructions for installation and commissioning
Hardware supplied in the Schneider Electric RPC Kit…
Proximity Sensor mounted behind crank arm
Load Cell Sensor installed on bridle
Run Interrupt Relay (RIR) mounted on DIN rail in cabinet
Integrated Machine Controller Card
Installed into drive
Schneider-built Enclosed Pumpjack Drive Cabinet
Enclosed drive comes with IMC card, relays, and other internal components
already installed (load cell and prox sensor must still be installed on site)
Door-on-door feature allows access to drive controls without opening cabinet
*The cabinet should already be mounted in its permanent position on site prior to arrival of the start up technician. Schneider Electric can also perform installation as a separately quoted job.
Schneider-approved technicians will mount the necessary RPC components into the drive*
Hardware Start Up Steps
Simple Commissioning Steps• Shut down all power to field drive• Install IMC into drive and connect
to power supply (kits only)• Install relays and connect to the
IMC (kits only)• Mount load cell onto bridle
(performed by customer) and connect cable to IMC
• Mount proximity sensor on pumpjack and connect cable back to IMC
• Power can now be restored to the drive cabinet
• Ready to set up operating parameters
Install the Load CellImportant: Load cells must be installed with local assistance. This will be coordinated with the customer prior to set up day.
Connect the Load Cell Cable to the Load Cell
Load cell cable, once connected, must be routed back to the drive cabinet and secured in such a manner so as to avoid entanglement or trip hazards (configuration shown may vary; for example only)
Proximity Sensor Bracket & Hardware
Be careful attaching magnets to the bracket - the
high-strength magnets create a
serious pinch hazard!
• Note very tight clearance between Proximity Sensor and crank arm, ensuring the best possible signal each time the arm passes the sensor
• Secure the cable using UV-resistant, outdoor-rated cable ties (or similar), and carefully route the cable back to the drive cabinet so as to avoid tripping hazards
Install the Proximity Sensor
RPC HMI Software Interface
RPC Configuration: Interface with the RPC Drive
HMI Configuration Software for PC• Minimum: 1 license required (typically 1 per PC used)
• 1 license will support multiple wells
RPC Configuration: Install RPC HMI Software
Installation CD and USB license key are included for software
Multiple Ways to Access the RPC
RPC Configuration: HMI Software, Hardware & OS Minimum Requirements: direct connection*
Component Minimum (1-2 wells only)
Processor Dual Core (2x) 2GHz CPU
RAM 2 GB
Operating System Windows XP Professional (SP3) or greater; or Windows Server 2003 (SP2) or greater.
Available Disk Space 500MB up to 100 GB (may require separate disk for historic data)
Graphics Adapter High performance graphics card
Browser Internet Explorer 6 or above (cannot use Firefox)
* Requirements will increase with number of wells to be accessed via the same system – confirm configuration ahead of time
RPC Configuration: Install RPC HMI SoftwareFollow the instructions that appear upon loading the Installation CD
Screen Shots/Features
Login/Landing Page• Choose between multiple wells to view
• Create/delete additional wells
• Manage user access
Status Page• Monitor well “vital signs”
• View Dynamometer Cards in real time
ATV Drive Configuration• Set up ATV71 drive parameters without using the drive keypad
• Transfer all the settings to the drive with the click of a button
Well Fault Detection• Pre-program how the RPC unit responds to problems/faults caused by
external factors…
• belt slippage, errant sensor readings, loss of signal, etc.
History Trends & Events• Choose from a variety of parameters to track
• View real-time data or look back at stored trends
History Cards• Look back at historic cards to diagnose well problems
• Cards are accessible in real time, or download the previous 18 stored cards
Pump Control Configuration• Set up all pumping parameters such as max/min speed, pump-off settings,
start-up alarms
• Customize pump-off wait times or let the RPC determine them for you
Well Data Configuration• Manage pump API data and calibrate strokes/minute vs. motor speed
• Add rod taper information and manage well parameters
Time & Network Configuration• Manage network set up, counters and timers
• Save well parameter settings and upload them to other wells
Get More Information…
Approved RPC Channel Reps and TerritoriesCompany Territory
Latech
Daco
Pantech
RDS
DMC-Carter Chambers
Westerman
Beabout Company
Industrial Automation Group
Utah, Western Wyoming, Idaho, Montana
Oklahoma, No. Arkansas, Kansas
West & Central Texas, Southern New Mexico
South Texas
Louisiana, East Texas
Western Pennsylvania, Ohio
Northern California (Bakersfield)
Northern New Mexico, Colorado, Eastern Wyoming, North & South Dakota, Montana
Berg Johnson Minnesota
Contact Schneider Electric to Inquire…
• See your local Schneider Electric Sales Person
• Call us directly at: 919-217-6491
• See the web site and download a brochure at: • http://www.schneider-electric.us/sites/us/en/solutions/industrial-
solutions/oil-gas/oil-and-gas-rod-pump.page