Fanning correlation

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The Fanning correlation is the name used to refer to the calculation of the hydrostatic pressure difference and the friction pressure loss for the dry gas flow.

Fanning correlation is the default VLP correlation for the dry gas wells in the PQplot.

Fanning in PQplot Vs Prosper & Kappa

Math & Physics

Following the law of conservation of energy the basic steady state flow equation is:

 144 \frac{\Delta p}{\Delta h} =  \rho_g + \rho_g \frac{f v_g^2 }{2 g_c D} + \rho_g \frac{\Delta{(\frac{v_g^2}{2g_c}})}{\Delta h}

Colebrook–White [1] equation for the Darcy's friction factor:

 \frac{1}{\sqrt{f}}= -2 \log \left( \frac { \varepsilon} {3.7 D} + \frac {2.51} {\mathrm{Re} \sqrt{f}} \right)[2]

Reynolds number:

 Re = 1488\ \frac {\rho_g v_g D}{\mu_g}
 \rho_g = \frac{28.967\ SG_g\ p}{z\ 10.732\ T_R} [3]
 v_{SG} = \frac{q_g \times 10^6}{86400 A_p}\ \frac{14.7}{p}\ \frac{T_K}{520}\ \frac{z}{1}


Why Fanning correlation ?

Fanning correlation actually is not a correlation, it's the fully explicit workflow to define the pressure drop.


 h = depth, ft
 f = friction factor, dimensionless
 p = pressure, psia
 Re = Reynolds number, dimensionless
 SG = specific gravity, dimensionless
 T = temperature, °R or °K, follow the subscript
 v = velocity, ft/sec
 z = gas compressibility factor, dimensionless

Greek symbols

 \varepsilon = absolute roughness, ft
 \mu = viscosity, cp
 \rho = density, lbm/ft3


g = gas
K = °K
L = liquid
R = °R
SG = superficial gas


  1. Colebrook, C. F. (1938–1939). "Turbulent Flow in Pipes, With Particular Reference to the Transition Region Between the Smooth and Rough Pipe Laws"Paid subscription required. Journal of the Institution of Civil Engineers. London, England. 11: 133–156. 
  2. Moody, L. F. (1944). "Friction factors for pipe flow"Paid subscription required. Transactions of the ASME. 66 (8): 671–684. 
  3. Lyons, W.C. (1996). Standard handbook of petroleum and natural gas engineering. 2. Houston, TX: Gulf Professional Publishing. ISBN 0-88415-643-5.