production · lift
Hydraulic Lift Piston Pump Flow Rate
click formula to derive ↑
Inputs
in
in
in
spm
Description
Computes the theoretical (idealized, 100%-fillage) daily displacement of a double-acting downhole hydraulic piston pump from its pump piston and connecting-rod diameters, stroke length, and pumping speed. Unlike a single-acting sucker rod pump, a hydraulic piston pump produces fluid on both the upstroke and downstroke, so the connecting rod's cross-section reduces the net displacement on one side of the cycle.
Variables
| Symbol | Unit | Description |
|---|---|---|
| PD | STB/d | Theoretical Pump Displacement (PD) |
| Dp | in | Actual current bore diameter of the downhole pump piston/plunger, from the pump's manufacturer specification. |
| Dr | in | Actual current diameter of the rod connecting the engine piston to the pump piston — occupies part of the pump barrel's cross-section on one stroke of a double-acting pump. |
| s | in | Length of the pump piston's full stroke. |
| N | spm | Pump cycling speed, in strokes per minute. |
Assumptions
- Pump is a standard double-acting design — fluid is displaced on both the upstroke and downstroke, with the connecting rod reducing net area on one side only
- The pump barrel fills completely with liquid on every stroke (100% theoretical fillage) — no allowance for gas interference, valve leakage, or slippage
- Dp and Dr are the pump's actual current bore and rod diameters, not nominal/new-pump specifications
Limitations
- Does not model the power-fluid rate required to drive this displacement, or the pump-to-engine (P/E) area ratio that relates the two — a separate power-fluid-requirement calc, out of scope here
- Does not account for slippage past piston seals or valve leakage, which reduce actual delivered volume below this theoretical figure — no hydraulic-lift-specific efficiency calc exists yet to quantify this shortfall, unlike Rod Pump Efficiency for sucker rod pumps
- Assumes single-phase liquid at the pump — no correction for free gas entering the pump barrel
Use Cases
- → Theoretical capacity check: Establish the maximum theoretical daily fluid volume a given hydraulic piston pump size, stroke, and speed can displace, before any real-world efficiency losses.
- → Pump/power-fluid sizing input: Use PD as the starting design figure when sizing the power-fluid rate and surface pumping unit required to drive the installation.
Related Calculations
Region Notes
Permian Basin
Hydraulic piston pumps see limited but persistent use in Permian wells with deviated or crooked-hole conditions that complicate sucker rod strings, and in wells where a closed power-fluid system is preferred to reduce surface footprint.
References
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