Schneider Electric Case Study
ATFAB
Fall Branch, Tennessee
Improve efficiencies and
save energy in natural gas
extraction with an automated
solution and remote access.
Make the most of your energySM
Schneider Electric Case Study > ATFAB
Challenge
Just like people, natural gas wells have their own unique and individual
characteristics. Even within the same gas field, some wells are super-producers,
while others consistently produce a low volume of gas. And similar to people, the
wells change on a daily basis depending on environmental factors. In a way, the
well is a natural, living thing, and utilizing a one-size-fits-all method to natural gas
production won’t yield the best results.
A customized approach was the premise for an automated pump jack solution
created by ATFAB, a system integrator and machine design company in Fall Branch,
Tenn. ATFAB was approached by an eastern United States natural gas production
company looking for an automated solution for its dewatering application that would
help them gain efficiencies in extraction, service, and maintenance, while also giving
them the ability to monitor and control the sites remotely.
In natural gas production, dewatering is the removal of built-up water from solid
material in a gas-producing well. A well is between 1,500 and 2,000 feet deep
and when it intersects with a water table, a pump jack is needed to move water
off the ground so the gas can move out. The more water, the more difficult it is for
the gas to escape. At the same time, pumping the well completely dry damages
the equipment. Therefore, there’s a fine balance between pumping the water out
so it’s at as low a level as possible, without actually pumping the well dry.
Prior to an automated solution, the gas company utilized a timer box and a
contactor. The well was either “on” or “off” for a predetermined amount of time
that an operator manually set.
Algorithms and smart PLC enable
condition-based pump jack
Working together with Schneider Electric™, The Global Specialist in Energy
Management™ that offers integrated solutions across multiple market
segments, ATFAB developed an automated pump jack solution with the Twido™
programmable logic controller (PLC), Altivar™ 312 variable frequency drive (VFD),
and Magelis™ XBT N400 and XBT-GT500 human machine interface (HMI).
ATFAB and Schneider Electric worked with the natural gas producer for several
years to develop a software program that accomplished everything the customer
was hoping for. The result was a pump jack solution that calculates how long it
should run based on site conditions, and shuts itself down when needed, rather
than run for a set amount of time.
ATFAB discovered that the pump on/off cycle was not always optimal and the
time required for pumping the water would vary based on current conditions.
“Some wells showed more than a 50 percent energy savings from not having to
run them in a time mode,” said Jeff Thornburg, operations manager, ATFAB. “We
also engineered the solution to allow the pump jacks to operate using threephase motors instead of a single-phase mode, which garnered additional energy
savings and maintenance costs by eliminating the capacitive start.”
The best part is that an algorithm in the PLC allows the pump jack to learn from
itself, and to make adjustments according to the unique characteristics of the
well that it’s controlling. After every cycle, the PLC examines how the pump jack
ran and recalculates how long it will stay off and the length of running time for the
next cycle based on current conditions.
ATFAB | 2
Schneider Electric Case Study > ATFAB
“We learned that the wells change
how much water is produced,
even on a daily basis depending
on the water table and other
factors. The new program allows
it to adapt for every cycle based
on the current conditions. As the
PLC sees conditions changing, it
automatically corrects itself.”
— Jeff Thornburg,
operations manager, ATFAB
“Through this process, we learned that the wells change how much water is produced,
even on a daily basis depending on the water table and other factors,” said Thornburg.
“The new program allows it to adapt for every cycle based on the current conditions.
As the PLC sees conditions changing, it automatically corrects itself.”
Thornburg’s partner, Jim Ward, engineering manager, confirms that ATFAB’s
success in this application is due in large part because they recognized that each
well had its own characteristics, and that those characteristics change daily.
“We were successful because we didn’t treat all the wells the same. They’re all
individual and different, and they’re always changing,” Ward said. “Essentially,
each well has its own customized solution.”
Even in extreme cases, the automated pump jack solution knows what to do.
For example, if there’s a power outage, the system will do a rewrite so the pump
knows that it needs to pump all the water out of the column before it can resume
optimal production of gas. With the time-based system, the pump jack would just
pump off the water at the top of the well, not actually getting the water level low
enough to allow gas to escape.
ATFAB wrote another algorithm that tells operators the position of the pump jack
in the well while it’s running. This allows an operator to evaluate every stroke and
know whether the pump jack is pumping water or nothing.
ATFAB accomplished the condition-based run time and positioning components
of the solution without adding sensors or any other hardware to the well head.
While most companies use sensors on the pump jack head itself, this is an
expensive and prohibitive practice since it’s a Class 1, Division 1 hazardous
location, requiring special equipment to avoid hazardous situations.
“In both instances we opted to write algorithms rather than run additional wires or
equipment,” said Thornburg.
Automatic pump-off function
ATFAB recently completed the newest software iteration for this application which
incorporates an automatic pump-off function. The well will automatically cease
pumping when the controller sees that the well is running out of water. When the
well is run dry, it burns the seals on the pump jack. While the seals themselves
are only a few dollars, their replacement requires the entire pump jack to be
pulled out of the well — this is not only expensive, but costs a great deal in lost
production.
“We expect the addition of the pump-off feature in the software to be a significant
cost savings opportunity for our customer,” said Ward.
Remote access simplifies field maintenance,
connectivity enabled by two-byte addressing
One of the natural gas production company’s other requirements for a solution
was remote monitoring and access to each well site via radio network. With one
well tender responsible for 80 wells, all in remote areas, it was especially difficult
to effectively manage them. Before the automated solution, the well tender’s only
option was to jump in a truck and drive out to the site.
ATFAB | 3
Schneider Electric Case Study > ATFAB
What made the remote monitoring aspect of the solution more challenging
though, was the number of devices that needed to be on the network —
including the VFD, modem, flow valve, flow computer, PLC, etc. — combined
with the high number of wells.
To move beyond this limitation, Schneider Electric was able to modify the
firmware in the PLC to accommodate two-byte Modbus addressing, which
extends the number of slaves in the network to 65 535.
“Two-byte addressing has been key to getting the automation on the customer’s
network so they can monitor the wells in real time,” said Ward. “Before, a well
tender needed to go to the well with an HMI to diagnose the status or a problem.
They wouldn’t even know if something was broken unless they happened
to check. Now, this information is available on the network and anyone from
anywhere can see the status and make control changes.”
Added Thornburg, “The two-byte addressing was not Schneider Electric’s
standard, but they were willing to modify it and meet the needs of the customer.”
The remote access also helps the customer monitor the water level in their 210
BBL tank that stores the pumped off water. Prior to the automated solution, the
customer would send someone to check the tank every few days. Now they save
time by checking the status remotely.
Ultimately, the automated pump jack solution has been a huge success for the
customer — achieving significant energy savings, a more efficient extraction
process, and remote access that allows for proficient service and maintenance.
To learn more about pump solutions, visit
www.schneider-electric.com
To learn more about ATFAB, visit their site at
www.atfab.org
Schneider Electric USA
Automation and Control Center of Excellence
8001 Knightdale Blvd.
Knightdale, NC 27545
Tel: 919-266-3671
www.schneider-electric.com/us
Document Number 0100AC1102
Schneider Electric Canada
19 Waterman Avenue
Toronto, ON M4B 1Y2
Tel: 1-800-565-6699
www.schneider-electric.com/ca
This document has been
printed on recycled paper.
October 2011
© 2011 Schneider Electric. All Rights Reserved. Schneider Electric, Make the most of your energy, The global specialist in energy management, Twido, Altivar, and Magelis
are trademarks owned by Schneider Electric Industries SAS or its affiliated companies. All other trademarks are property of their respective owners. 998-8866_US
The automated solution uses the Modbus open communication protocol which
transmits information serially between electronic devices. In a standard Modbus
network there is one master and up to 247 slaves, each one with a unique
address. This limits the number of devices on the network to 247, which severely
limited the number of wells on each radio network.