Critical Flow Rate Calculator
Calculate the minimum gas flow rate required to continuously unload liquids from gas wells using Turner (1969) and Coleman (1991) methods.
Input Parameters
Turner: Vt = 1.593 [σ(ρL-ρg)]^0.25 / ρg^0.5 | Coleman: same with 20% reduction
Turner Velocity
--
ft/s
Turner Rate
--
Mscf/d
Coleman Velocity
--
ft/s
Coleman Rate
--
Mscf/d
Gas Density
--
lb/ft³
Liquid
Water
Critical Rate vs Wellhead Pressure
How this was calculated
Turner (1969): Vt = 1.593 * [σ(ρL - ρg)]^0.25 / ρg^0.5, with 20% upward adjustment. Uses σ = 60 dyne/cm for water, 20 for condensate.
Coleman (1991): Same equation without the 20% adjustment. Found to match field data for low-pressure wells better.
Rate conversion: q = 3.06 * Vt * P * A / (T * Z), where A is tubing cross-section area.
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Calculate flowing BHP and plot tubing performance.
Open Tool →Struggling with liquid loading in your gas wells? We can help optimize your artificial lift strategy.
Book a free strategy call →Understanding Critical Gas Flow Rate and Liquid Loading
Liquid loading is a common problem in mature gas wells where the gas velocity in the tubing drops below the critical rate needed to carry liquid droplets to the surface. When this happens, liquids accumulate in the wellbore, increasing the hydrostatic pressure and further reducing gas production, which can eventually kill the well. Identifying the critical flow rate is the first step in managing liquid loading.
Turner et al. (1969) developed the most widely used critical velocity model based on the terminal velocity of the largest liquid droplets in the gas stream. The model accounts for interfacial tension, liquid density, and gas density. Coleman et al. (1991) later found that Turner's 20% upward adjustment was unnecessary for low-pressure wells. Both methods are useful screening tools, though actual critical rates depend on flow patterns and wellbore geometry. This calculator implements both. Built by Groundwork Analytics.