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Field guide

Pump-Off Controller vs. AI Well Control

Short answer: a pump-off controller (POC) protects a rod-pumped well by switching it off when it pumps off, then restarting it after an idle period. A variable-speed drive (VSD) lets the controller slow the pump instead of stopping it. AI well control adds fleet-wide card reading and closed-loop speed control on a measured fluid level, so the pump is kept matched to inflow rather than cycled on and off. Each step adds capability, and also adds data, integration and trust requirements.

By SRABS Engineering ·
Article / What does a pump-off controller do?

What does a pump-off controller do?

A pump-off controller measures rod load and position on every stroke, recognises the dynamometer-card shape of a pumped-off well, and shuts the unit down for an idle period so the fluid level can recover before it restarts. 12

The classic design uses a load cell on the polished rod and a position transducer. From the well's own maximum and minimum loads the controller sets a reference point. As the well pumps off, the downstroke load curve shifts on successive strokes; when it crosses the set point, the controller stops the motor. 1 In card terms, it's watching the bottom-right corner of the card disappear (see the dynamometer card atlas).

Before pump-off controllers, the usual method was a timer: run the pump for a set time, then turn it off so the well can refill. 3 A POC replaces the guess with a measurement.

What POCs do well:

  • They are proven, standalone and well understood by field crews.
  • They need no network to protect the well: the decision is made at the wellhead.
  • They stop the worst of fluid pound, which damages the rod string and the pump. 4
Article / Where on/off control runs out

Where on/off control runs out

On/off control trades pounding for idle time. The well has to pump off before the controller acts, and every hour shut in is an hour not producing. Each well also needs its own setpoints, tuned and re-tuned as it changes. 234

  • It reacts, it doesn't prevent. A Shell patent on controlling rod-pumped wells notes that earlier controllers generally needed the well to actually pump off before stopping it, so the well pounded first. 2
  • Idle time costs production. Lengthening idle time reduces the number of pounding strokes, but the same patent points out that it also reduces production from the well. 2
  • Start-stop has its own wear. A patent on variable-speed control describes the run-then-stop approach as able to cause excessive wear, or even catastrophic failure, of the pumping unit. 3
  • Setpoints drift. A setpoint chosen at commissioning reflects the well as it was. As inflow declines, water cut rises or gas rates change, the setpoint needs tuning. On a fleet of hundreds of wells, that tuning falls behind.
  • One well at a time. A POC knows its own well. It doesn't compare cards across the field or rank which wells need attention first.
Article / Variable-speed drives: slow down instead of shutting in

Variable-speed drives: slow down instead of shutting in

A variable-speed drive lets the controller change strokes per minute continuously, so a well that's starting to pump off can be slowed to match its inflow instead of being stopped. It keeps the well producing and reduces start-stop cycles, but it is only as good as the signal it's controlled from. 345

The idea is straightforward: if the pump is displacing more than the well delivers, move it more slowly. Patents describe controllers that vary pumping speed automatically, including to adapt to changes in oil viscosity, 3 and methods that estimate pump fillage on each stroke, here from motor torque, and step the speed up or down within set limits. 4 A short-course paper on advanced rod pump control describes holding the fluid level at a predefined height above the pump to keep the pump full. 5

The limits are practical. The same paper notes that VSD control of rod pumps "has been tried with varying results," citing surface-equipment reliability, regeneration, harmonics and power factor among the issues. 5 And a VSD needs a good input. If the speed loop runs on an inferred fill estimate alone, it inherits that estimate's errors; with a direct fluid-level reading, it can control on the quantity it actually cares about.

Article / SCADA analytics and AI well control

SCADA analytics and AI well control

AI well control adds two things on top of a VSD: reading every card across a fleet automatically, and closing the speed loop on measured well conditions within limits the operator sets. It brings fleet-scale diagnosis and fewer manual setpoints, and it needs data, connectivity and a clear say in who controls the well. 6

Fleet-wide card classification. SCADA systems have long collected cards and alarms remotely; the newer step is machine-learning models that classify them. A 2025 Southwestern Petroleum Short Course paper reports models identifying twelve non-normal operating conditions, including fluid pound, gas interference, worn pumps and rod parts, at 85–95% accuracy as reported by its authors. 6 That turns thousands of cards a day into a ranked list of wells to look at.

Closed-loop control. The control step goes further than alerting: the system adjusts pump speed itself, inside guardrails, using the card, motor data and fluid level together. The aim is a pump that stays matched to inflow, without the pound-idle-restart cycle.

What AI control needs from you, stated fairly:

  • Data and connectivity. Cards, motor data and ideally fluid level, reaching the controller reliably.
  • Integration. It has to talk to the drives and SCADA already in the field, not replace them.
  • Guardrails and a way out. Operators need to set the limits (speed range, fillage targets, kill conditions) and keep the authority to override.
schematic · control loops by category
FIG. C Control options for a rod-pumped wellThree ways to control a rod-pumped well, as block diagrams. A timer runs and stops the motor on a schedule with no input from the well. A pump-off controller reads the dynamometer card, compares it with a pump-off setpoint and stops the unit for an idle period; it acts after the well pumps off. Closed-loop speed control reads the card, motor data and fluid level, decides within operator guardrails and sets pump speed through a variable-speed drive, so the loop closes on every stroke.FIG. CCONTROL LOOPS — BY CATEGORY01TIMERSENSEclockDECIDErun / stop on a scheduleACTmotor on · offWELLrod pumpno return path from the wellopen loop · no input from the well02PUMP-OFFCONTROLLERSENSEcard: load + positionDECIDEpump-off setpointACTstop · idle · restartWELLrod pumpnext card, after pump-offacts after the well pumps off03CLOSED-LOOPSPEED CONTROLSENSEcard · motor · fluid levelDECIDEinside operator guardrailsACTVSD sets pump speedWELLrod pumpthe loop closes on every strokespeed matched to inflow, every strokeDWG FIG. CSCALE NTSSRABS
FIG. C Control options for a rod-pumped wellThree ways to control a rod-pumped well, as block diagrams. A timer runs and stops the motor on a schedule with no input from the well. A pump-off controller reads the dynamometer card, compares it with a pump-off setpoint and stops the unit for an idle period; it acts after the well pumps off. Closed-loop speed control reads the card, motor data and fluid level, decides within operator guardrails and sets pump speed through a variable-speed drive, so the loop closes on every stroke.FIG. CCONTROL LOOPS01 TIMERopen loop · no input from the wellSENSEclockDECIDErun / stop on a scheduleACTmotor on · offWELLrod pump02 PUMP-OFF CONTROLLERacts after the well pumps offSENSEcard: load + positionDECIDEpump-off setpointACTstop · idle · restartWELLrod pump03 CLOSED-LOOP SPEED CONTROLspeed matched to inflow, every strokeSENSEcard · motor · fluid levelDECIDEinside operator guardrailsACTVSD sets pump speedWELLrod pump
Article / Comparison: control options by category

Comparison: control options by category

TimerPump-off controllerPOC + VSDAI well control (closed loop)
Main inputClockRod load and position (the card) 1Card, or an inferred fill / torque estimate 4Card, motor data and fluid level, across the fleet
ActionRun, stop on schedule 3Stop on pump-off, restart after idle 1Change speed to match inflow 34Change speed within operator guardrails; rank alerts
Fluid poundFrequent when the timer is wrongLimited, but the well pounds before it stops 2Reduced, if the speed signal is goodAimed at preventing it before it starts
Production during controlLost while offLost during idle time 2Kept producing at lower speedKept producing, matched to inflow
Tuning effortConstant guessworkSetpoints per well, drift over timeSpeed limits and setpoints per wellGuardrails per well; fewer manual setpoints
Works without networkYesYesYesNeeds data connectivity
Fleet viewNoneNoneNoneYes
Article / Where SRABS Brain fits

Where SRABS Brain fits

SRABS Brain is "the artificial lift optimization layer of the SRABS stack." In the platform page's words, it "reads the Pump, Echo, and your existing SCADA via a plug-and-play interoperable API, and runs the well for you. An autonomous rod pump controller, in software."

"Brain reads every dynamometer card, motor current and Echo fluid level, and checks them against the physics of your rod string. When a card starts drifting toward buckling or pump-off you get a ranked alert with days-to-failure, and on autopilot wells it retunes the VSD before the failure happens." It "runs within the guardrails you set" (SPM range, fillage targets, kill conditions), and "Brain talks to your existing VSDs, Lufkin, Eaton, ABB, whatever." No SCADA replatform.

See the platform, solutions and how it works. To estimate what fewer failures would mean on your own fleet, run the ROI calculator. Its default 100-well scenario is modelled, not a field result.

Article / The bottom line

The bottom line

Timers guess, pump-off controllers react, VSDs adjust, and closed-loop control keeps the pump matched to the well. A POC is still the right baseline protection for a well. The question is whether reacting to pump-off well by well is enough for the fleet you run, or whether it's worth controlling on fluid level and reading every card automatically.

Test it where it's easiest to judge: one well, with your own guardrails.

Loan us a well →
Article / FAQ

FAQ

What does a pump-off controller do?

It measures rod load and position on every stroke, detects the card shape of a pumped-off well, and shuts the unit down for an idle period so the fluid level can recover before restarting.

What is the difference between a pump-off controller and a VSD?

A pump-off controller switches the well off and on. A variable-speed drive lets the controller change the pumping speed instead, so the well can be slowed to match inflow and keep producing.

Do pump-off controllers stop fluid pound?

They limit it. A classic controller acts once the well has pumped off, so some pounding happens before it stops, and the idle time that follows also costs production.

What is AI well control for rod pumps?

Software that reads dynamometer cards and other well data across a fleet, flags problems automatically, and adjusts pump speed in a closed loop within limits set by the operator.

Does AI well control replace my SCADA or controllers?

It shouldn't have to. Look for a system that reads from the SCADA you already run and sends commands to the drives and controllers already installed. SRABS Brain works that way.

Can I keep control of the well with AI control?

You should. Look for operator-set guardrails such as speed range, fillage targets and kill conditions, with alerts for exceptions and the ability to override.

Article / Sources

Sources

  1. US Patent 4,487,061, "Method and apparatus for detecting well pump-off" (FMC Corporation, 1984). https://patents.google.com/patent/US4487061
  2. US Patent 5,314,016, "Method for controlling rod-pumped wells" (Shell Oil Company, 1994). https://patents.google.com/patent/US5314016
  3. US Patent 5,251,696, "Method and apparatus for variable speed control of oil well pumping units" (1993). https://patents.google.com/patent/US5251696
  4. US Patent 10,408,205, "Method of determining pump fill and adjusting speed of a rod pumping system" (Schneider Electric Systems Canada, 2019). https://patents.google.com/patent/US10408205
  5. Torseke, E., Polk, T., Boren, S., "Advanced Rod Pump Control: New Patent Pending Technologies That Optimize Production, Reduce Maintenance, and Save Energy When Applied to Rod-Pumped Wells," Southwestern Petroleum Short Course. https://www.swpshortcourse.org/paper/advanced-rod-pump-control-new-patent-pending-technologies-optimize-production-reduce
  6. Bambekov, I., Hecht, J., Sim, W., "Accelerating Rod Lift Optimization Through AI-Powered Dynacard Analysis: Field-Validated Results," Southwestern Petroleum Short Course, paper 2025031. https://www.swpshortcourse.org/paper/2025031-accelerating-rod-lift-optimization-through-ai-powered-dynacard-analysis-field