production · multiphase flow
Turner Liquid Loading
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Inputs
mN/m
lb/ft³
lb/ft³
in
ft³/scf
Description
Computes the critical (minimum) gas velocity and corresponding minimum gas rate required to continuously remove entrained liquid droplets from a gas well, using Turner, Hubbard & Dukler's (1969) droplet model with their field-recommended ~20% upward adjustment — the version of 'the Turner equation' actually used in industry practice, not the bare theoretical constant. Below this rate, liquid falls back down the tubing (liquid loading), progressively restricting and eventually killing gas flow.
Variables
| Symbol | Unit | Description |
|---|---|---|
| vt | ft/s | Critical (Minimum) Gas Velocity |
| qmin | Mscf/d | Minimum Gas Rate to Avoid Loading |
| σ | mN/m | Interfacial tension between the gas and liquid phases at local flowing conditions. Always entered in mN/m (=dyne/cm, numerically identical) regardless of the active unit toggle, same convention as Multiphase Gradient (Beggs-Brill). |
| ρL | lb/ft³ | Density of the entrained liquid (condensate or produced water) at flowing conditions. |
| ρG | lb/ft³ | Density of the gas phase at local flowing conditions. No dedicated gas-density calculator exists yet on this platform (same gap flagged by Multiphase Gradient's own limitations); estimate from the real gas law using a gas gravity/molecular weight and a Z-factor from the Gas Z-Factor calculator. |
| d | in | Internal diameter of the tubing or pipe at the point where liquid-loading onset is being checked. |
| Bg | ft³/scf | Gas formation volume factor at the flowing pressure/temperature of interest, needed to convert the critical (actual, in-situ) velocity into a minimum standard-condition gas rate — the same conversion Gas Velocity uses in reverse. Run the Gas FVF (Bg) calculator first and carry its result in here (see relatedCalcs). |
Assumptions
- The reservoir/well produces a continuous mist of entrained liquid droplets in a predominantly gas stream — the droplet model does not describe liquid-film-dominated or slug-flow loading mechanisms
- Newton's drag regime applies (CD=0.44) at the relevant droplet Reynolds numbers — Turner's own derivation and this platform's independent re-derivation both adopt this standard assumption
- The field-adjusted (not bare theoretical) constant is used, matching standard industry practice for predicting actual liquid-loading onset
- Vertical or near-vertical flow — Turner's model was developed and validated for vertical gas wells
Limitations
- An empirical/semi-theoretical droplet model calibrated against a specific historical dataset — even with the field adjustment, subsequent studies have found Turner's method can still under-predict loading onset in some cases; newer models (e.g. Li, Guo/Ghalambor closed-form refinements) claim improved accuracy but are not implemented on this platform
- Does not account for deviated/horizontal well sections, where liquid-loading mechanisms differ from the vertical droplet model this calculator implements
- No dedicated gas-density calculator exists yet on this platform (same gap as Multiphase Gradient) — ρG is a direct numeric entry with representative-range guidance rather than a linked calculator result
- The primary source (Turner, Hubbard & Dukler, 1969, JPT) remains paywalled/inaccessible — this calculator's constant was independently re-derived from first principles and cross-checked against a secondary-source-reported theoretical constant, not transcribed from the original paper's own worked example, which was not accessible.
Use Cases
- → Liquid-loading diagnosis: Determine whether a gas well's current rate is above or below the critical rate needed to keep produced liquid moving continuously to surface.
- → Tubing/completion sizing for deliquification: Size (or re-size, via velocity string / plunger lift / other deliquification method planning) tubing so a declining gas well stays above its critical unloading rate longer into its producing life.
Related Calculations
Region Notes
Global
Liquid loading is the dominant late-life production problem for most conventional and unconventional gas wells — as reservoir pressure depletes, declining rate eventually falls below the critical rate computed here, and a deliquification method (plunger lift, gas lift, velocity string, artificial lift) becomes necessary to sustain production.
References
Primary source
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