Variable frequency drives rod pump control podcast

Introduction to Variable Frequency Drives and Rod Pump ControlFreddy Jones, Manager – Offer Development

Variable Frequency Drives Overview


By 2050, demand for energy will have doubled, but CO2 emissions must be cut in half!


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


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



• 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…

http://www.serelays.com/flash/vsd/

http://www.serelays.com/flash/vsd/


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



• 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


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


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.


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


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


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


“Load” consists of the weight of the fluid + the weight of the rod string as measured by the load cell

Maximum Load


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


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


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


A, B

C, D

DownstrokeMinimum Load


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


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


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

Variable frequency drives rod pump control podcast

Technology

Transcript of Variable frequency drives rod pump control podcast