Gas well critical-velocity (Turner / Coleman / Lea) calculator for Python.
A small, dependency-free library for computing the minimum gas velocity (and corresponding standard-condition rate) required to lift water or condensate droplets out of a vertical gas well's tubing. Below the critical rate, the well is at risk of liquid loading: droplets accumulate, hydrostatic head builds, and gas inflow from the formation chokes off.
This is the Python companion to the free interactive calculator at wellrx.app/tools/critical-velocity/.
For background and a 24-hour decision tree on what to do when these signals fire, see 7 Early-Warning Signs of Gas Well Liquid Loading.
pip install wellrx-tclfrom wellrx_tcl import compute, compute_all, recommended_correlation
# One correlation at a time
result = compute(
tubing_id_in=2.441, # 2-7/8" OD tubing
flowing_pressure_psia=500,
flowing_temperature_f=110,
gas_specific_gravity=0.65,
z_factor=0.90,
fluid="water", # or "condensate" or "mixed"
correlation="turner", # or "coleman" or "lea"
)
print(result)
# Turner: v_c = 2.04 ft/s q_c = 197 Mcfd
# All three correlations at once
results = compute_all(tubing_id_in=2.441, flowing_pressure_psia=500, flowing_temperature_f=110, fluid="water")
for r in results.values():
print(r)
# Turner: v_c = 2.04 ft/s q_c = 197 Mcfd
# Coleman: v_c = 1.69 ft/s q_c = 163 Mcfd
# Lea: v_c = 1.49 ft/s q_c = 144 Mcfd
# Heuristic for which correlation to trust
print(recommended_correlation(500)) # 'lea'
print(recommended_correlation(150)) # 'coleman' — Turner over-predicts low-pressure| Correlation | Year | Best for | Why |
|---|---|---|---|
| Turner | 1969 | Field default, high-pressure (>2000 psia) | Most conservative; 20% padding over the spherical-droplet drag derivation. Tends to over-predict on mature low-pressure wells. |
| Coleman | 1991 | Low-pressure mature wells (FTP < 500 psia) | Same form as Turner without the 20% padding. Better fit for unconventional / depleted gas wells. |
| Lea / Nickens | modern | Vertical / near-vertical wells with characterized PVT | k chosen at 1.4 for typical fluid load. The current engineering reference. |
Run recommended_correlation(p_psia) for a quick by-pressure-regime hint.
Each compute() call returns a CriticalResult dataclass:
@dataclass
class CriticalResult:
correlation: str # "turner" | "coleman" | "lea"
v_c_ft_s: float # critical velocity, ft/s
q_c_mcfd: float # critical rate at standard conditions, Mcfd
rho_g_lb_ft3: float # computed gas density at flowing conditions
tubing_id_in: float
tubing_area_in2: float
flowing_pressure_psia: float
flowing_temperature_f: float
gas_specific_gravity: float
z_factor: float
fluid: str- Field-form coefficients use Lea-form
K × [σ(ρ_L−ρ_g)]^0.25 / ρ_g^0.5withK = {turner: 1.92, coleman: 1.59, lea: 1.40}. - Critical rate uses
Q_sc = 3056 × P × v × A_ft² / (T × Z)(T in °R), which carries the conversion from actual to standard conditions and ft³/s → Mcfd. - The library is a planning estimate. For production decisions, validate against the well's documented loading history and PVT.
- Deviated / horizontal wells past ~30° inclination need an inclination-corrected approach not provided by Turner / Coleman / Lea alone.
- Turner, R. G., Hubbard, M. G., & Dukler, A. E. (1969). Analysis and Prediction of Minimum Flow Rate for the Continuous Removal of Liquids from Gas Wells. Journal of Petroleum Technology, 21(11), 1475–1482.
- Coleman, S. B. et al. (1991). A New Look at Predicting Gas-Well Load-Up. Journal of Petroleum Technology, 43(03), 329–333.
- Lea, J. F., Nickens, H. V., & Wells, M. (2008). Gas Well Deliquification. Gulf Professional Publishing.
Apache-2.0. See LICENSE.
- Free interactive calculator: wellrx.app/tools/critical-velocity/
- Field guide: 7 Early-Warning Signs of Gas Well Liquid Loading
- Plunger lift checklist: 21-point optimization checklist
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