production · lift
Rod Pump Efficiency
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Inputs
STB/d
STB/d
Description
Computes sucker rod pump volumetric efficiency — the ratio of a well's actual measured production rate to its pump's theoretical (100%-fillage) displacement — from Rod Pump Displacement's own output and a measured actual rate. A single lumped figure summarizing how much of theoretical pump capacity is actually being realized.
Variables
| Symbol | Unit | Description |
|---|---|---|
| Ev | % | Volumetric Pump Efficiency |
| Qactual | STB/d | Actual measured surface production rate, from a well test or metered/tank-gauged figure — a representative rate, not an instantaneous or transient reading. |
| PD | STB/d | Theoretical pump displacement at the well's actual current operating stroke length and speed — run the Rod Pump Displacement (PD) calculator first and carry its result in here. |
Assumptions
- Qactual is a representative rate from a well test or tank-gauged figure, not an instantaneous or transient reading
- PD is computed at the well's actual current operating stroke length and speed, not a nameplate or design-point figure from a different operating condition
Limitations
- This is a lumped efficiency figure — it does not decompose the shortfall into its individual causes (gas interference, fluid pound, worn barrel/plunger slippage, valve leakage)
- A low Ev alone cannot distinguish a pumped-off well (inflow-limited) from a mechanical problem (slippage, leaking valves) — that distinction requires a dynamometer card, which this calculator does not analyze
- Does not correct for free gas in the pump barrel, which lowers Ev independent of any mechanical fault
Use Cases
- → Pump performance screening: Quickly check how much of a pump's theoretical capacity is actually being realized, as a first screen before deeper dynamometer-card diagnostics.
- → Workover/optimization candidate ranking: Rank wells by volumetric efficiency to prioritize which sucker rod installations most need a dynamometer survey or workover.
Related Calculations
Region Notes
Permian Basin
Wolfcamp/Bone Spring sucker rod wells commonly run 60-85% volumetric efficiency when healthy; efficiencies well below 50% are a common early trigger for a dynamometer survey to distinguish a pumped-off well from gas interference or fluid pound.
References
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