Dynamometer Card Interpretation: An Atlas of Pump Card Shapes

What is a dynamometer card?

A dynamometer card is a plot of rod load against rod position over one pump stroke. It is the main diagnostic record for a rod-pumped well: the shape of the loop shows how the pump fills, how the valves work, and what the rod string and surface unit are carrying. ¹²

A dynamometer, the load-measuring instrument also called a dynagraph, records load at the polished rod as the unit strokes. Plotted against position, one stroke traces a closed loop: the upstroke along the top, the downstroke along the bottom. The SLB Energy Glossary lists what card analysis can reveal: a defective pump, leaky tubing, an unbalanced pumping unit, a partly plugged gas anchor, a gas-locked pump, an undersized unit. ¹

Every rod-lift engineer reads cards, from Permian and Bakken horizontals to heavy-oil wells in Alberta and Colombia and mature fields in Oman. The shapes are the same everywhere because the physics is the same.

Surface card vs. downhole pump card

The surface card is what the load cell at the polished rod measures. The downhole pump card is calculated from it, removing the rod string's stretch, weight and wave effects so you see the loads at the pump itself. Most diagnosis is done on the pump card. ²

The rod string between the surface and the pump is thousands of feet of elastic steel. Loads travel along it as stress waves, the rods stretch and contract, and friction damps the motion. So the surface card is the pump card filtered through the rod string. Early in rod-lift practice this made diagnosis hard: Gibbs' 1967 patent notes that the diversity of surface card shapes often made it impossible to read downhole conditions from the polished-rod card alone. ²

The fix was to calculate the pump card. Gibbs modelled the rod string as a damped wave equation, used the measured surface load and position as boundary conditions, and solved for load and position at the pump. ² That calculated card is the downhole pump card, and the textbook shapes below are drawn on it.

How to read the axes: position runs left to right from the bottom of the stroke to the top. Load runs bottom to top, from zero (or the buoyant rod weight) to the full fluid load. The upstroke runs along the top of the loop, left to right; the downstroke runs back along the bottom.

The full-pump card: the reference shape

A full-pump card is close to a rectangle. The pump picks up the full fluid load right at the start of the upstroke, carries it to the top, and drops it right at the start of the downstroke. Every other shape is read as a departure from it. ³

The valve sequence makes the rectangle:

1. Bottom of stroke → upstroke starts. The traveling valve closes and the plunger picks up the fluid column. Load rises almost vertically on the left side of the card.
2. Upstroke. The standing valve opens and the barrel fills while the plunger lifts the fluid load: a flat top line.
3. Top of stroke → downstroke starts. The standing valve closes, the traveling valve opens, and the fluid load transfers off the rods. Load drops almost vertically on the right side. A diagnostics patent describes this transfer at the top of stroke for a full or nearly full barrel as ideal pump operation. ³
4. Downstroke. The plunger moves down through liquid with the traveling valve open: a flat bottom line at low load.

Sharp corners mean the valves are opening and closing cleanly, and the height of the card is the fluid load. Keep this shape in mind for everything below.

Fluid pound: the bottom-right corner cut off

A fluid-pound card holds full load into the downstroke and then drops it suddenly partway down. The bottom-right corner is missing, and the near-vertical drop marks where the plunger hits liquid. The further left the drop, the emptier the barrel. ³⁴

On a pumped-off well the barrel only partly fills on the upstroke. At the top of the stroke there is no liquid under the plunger to open the traveling valve, so the rods keep carrying the fluid load while the plunger falls through low-pressure gas. When it hits the liquid, the valve opens and the load comes off all at once. The SLB glossary describes rod load falling by thousands of pounds in a fraction of a second. ⁴ The diagnostics patent describes the same thing in timing terms: the load transfer happens after the top of stroke instead of at it. ³

Fillage is read straight off the card: the distance from the left side to the drop, divided by the stroke length.

→ Full field guide: Fluid pound: what causes it and how to stop it

Gas interference: the same corner, rounded

A gas-interference card also loses the bottom-right corner, but the load comes off gradually along a curve instead of in one sharp drop. That curve is gas in the barrel being compressed until it opens the traveling valve. ⁵

Gas enters the pump with the liquid. On the downstroke the plunger first has to compress that gas, and the SLB glossary notes the gas builds enough pressure to open the traveling valve before the valve reaches liquid, so the valve opens slowly instead of with the sharp load change of fluid pound. ⁵ On the card that shows as a rounded, sloping unload instead of a cliff.

Telling the two apart from the card alone isn't always possible. A fluid-level reading settles it: gas interference usually has fluid well above the pump, while fluid pound means the well is pumped off. The glossary adds that gas interference itself doesn't cause premature equipment failure, but it signals poor pump efficiency. ⁵

Gas lock is the extreme case: so much gas that the traveling valve never opens. The card collapses into a thin loop, because the fluid load is never picked up and dropped.

→ Full field guide: Gas-locked rod pump: how to diagnose and fix gas lock

Leaking traveling valve or worn plunger: the top corners round off

When fluid slips back past the traveling valve or a worn plunger, the pump picks up load late at the start of the upstroke and loses it before the top. The top-left and top-right corners round off, and the top line sags below full fluid load.

On the upstroke the traveling valve and plunger hold the fluid column. If either leaks, part of the column slips back into the barrel, so the load builds slowly instead of instantly and starts bleeding off before the stroke ends. The faster the leak, the rounder the card.

Leaking standing valve: the bottom corners round off

A leaking standing valve lets fluid in the barrel escape back down while the plunger falls. The fluid load comes off late and slowly at the top of the stroke, and load starts coming back before the bottom, so the bottom corners round off and the downstroke runs above its normal level.

On the downstroke the standing valve should hold the fluid in the barrel so the plunger can pass through it with the traveling valve open. If the standing valve leaks, pressure under the plunger bleeds off, the traveling valve doesn't open cleanly, and part of the fluid load stays on the rods. The cure is mechanical: pull and repair the pump. Diagnosis is usually confirmed with a valve check: stop the unit and watch whether load holds.

Pump tagging: a spike at the end of the stroke

When the pump is spaced too close, the plunger hits the bottom (tagging down) or top (tagging up) of the pump at the end of a stroke. The card shows a sharp load spike at the left end (tagging down) or the right end (tagging up).

Operators sometimes space a pump to tap bottom on purpose, to jar a gas-locked traveling valve open. Repeated tagging sends impact loads through the pump, the rods and the surface unit, so treat a tagging card as something to fix with re-spacing, not something to live with.

Unanchored tubing: the sides lean over

If the tubing isn't anchored, it stretches when the fluid load moves onto the rods and springs back when the load moves off. The load pickup and release happen over a distance instead of instantly, so the left and right sides of the card lean into a parallelogram.

The leaning sides represent plunger travel lost to tubing movement: stroke that moves the tubing instead of displacing fluid. A tubing anchor holds the tubing in tension and squares the card back up. A leaking pump can make the left side lean in a similar way, so check the valves before blaming the anchor.

Parted rods: a thin, flat card

When the rod string parts, the unit lifts only the rods above the break and no fluid load. The surface card collapses into a thin, flat band at low load, and production stops.

The flat card sits at the weight of whatever rod string is still hanging, so its height above zero gives a rough idea of how deep the part is. A stuck-open valve can also produce a flat card with no fluid load, so pulling reports confirm which it is.

The buckling signature: the downstroke sags below zero

On a well where the bottom of the rod string buckles, the downstroke load line sags where the string goes slack into compression. On the calculated pump card, the downstroke load drops below zero: the bottom rods are being pushed, not pulled.

Rods are built to carry tension. On the downstroke, pump friction, fluid friction through the traveling valve and viscous drag resist the plunger's fall, and below the neutral point that resistance puts the rods into compression. A pump card running below the zero-load line on the downstroke is the most direct sign of it. Fluid pound and gas both add to that downstroke compression, so buckling often appears next to the shapes above.

This is the shape SRABS Brain looks for. In the words of the mechanism page: "Brain’s classifier is trained on that shape, so it flags buckling from the surface card alone. No downhole sensor required."

→ Full field guide: Sucker rod buckling: causes, damage and prevention

Reading cards across a whole fleet

One engineer can read a few dozen cards a day. A fleet produces thousands. That gap is why card classification has moved to automated pattern recognition: first load-and-position pump-off controllers, now machine-learning classifiers trained on labelled cards. ⁶⁷

The first automation was pump-off control. A classic controller measures rod load and position on every stroke, sets a reference point from the well's own maximum and minimum loads, and shuts the unit down when the downstroke load curve crosses it: fluid pound detection by card shape. ⁶

Current work goes further. A 2025 Southwestern Petroleum Short Course paper reports machine-learning models identifying twelve non-normal operating conditions, including fluid pound, gas interference, worn pumps and rod parts, with 85–95% accuracy as reported by its authors. ⁷

SRABS Brain "reads every dynamometer card, motor current and Echo fluid level, and checks them against the physics of your rod string," and on autopilot wells it "retunes the VSD before the failure happens." See the platform, how it works, and the modelled scenarios on cases. To estimate what fewer failures would mean on your fleet, run the ROI calculator. Its default 100-well scenario is modelled, not a field result.

The bottom line

Every card is a full-pump rectangle with something taken away, and what's missing tells you what's wrong. A cut corner is fillage, a rounded corner is gas or a leak, a leaning side is tubing, a spike is spacing, a flat line is a part, and a downstroke below zero is buckling.

If you're reading cards one well at a time and finding problems after they've cost a pull, test fleet-wide card reading and closed-loop control on one well.

FAQ

Sources

1. SLB Energy Glossary, "dynamometer card." https://glossary.slb.com/en/terms/d/dynamometer_card
2. Gibbs, S. G., US Patent 3,343,409, "Method of determining sucker rod pump performance" (Shell Oil Co., 1967). https://patents.google.com/patent/US3343409
3. US Patent 10,472,948, "Diagnostics of downhole dynamometer data for control and troubleshooting of reciprocating rod lift systems" (Weatherford, 2019). https://patents.google.com/patent/US10472948
4. SLB Energy Glossary, "fluid pound." https://glossary.slb.com/en/terms/f/fluid_pound
5. SLB Energy Glossary, "gas interference." https://glossary.slb.com/en/terms/g/gas_interference
6. US Patent 4,487,061, "Method and apparatus for detecting well pump-off" (FMC Corporation, 1984). https://patents.google.com/patent/US4487061
7. 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