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 Conversion from permeability to kf-value
basics the hydraulic conductivity coefficient (kf-value) contains a viscosity dependant term ( ? g ?-1) .
Since the kf-value is mainly used for groundwater this term may be treated as a constant ( approximately 7.5 106 at temp= 10°C and a density of 1000 kg m-3) and it is already contained in the kf-value.
For calculations in geothermal systems or for calculations in multy-phase-systems with different temperatures and different viscosities the permeability has to be used.
equation kf = K ? g ?-1
parameters
name  unit description  typ. value
t °C temperature 10
kf m s-1 hydraulic conductivity coefficient 1 10-5
K m2 permeability 1 10-12
? kg m-3 density 1000
g m s-2 acceleration of gravity 9.81
? kg m-1 s-1 dynamic viscosity 1.0 10-3
? m2 s-1 kinematic viscosity  1.0 10-6
factor m-1 s-1  conversion factor K to kf 7.5 106
dyn. viscosity? the dynamic viscosity? is temperature dependant. For water it is:
? [kg m-1 s-1] = 1.78 10-3 ( 1 + 0.0337 t + 0.000221 t2 )-1
basic equation kf = K ? g ?-1 with factor = ? g ?-1 we get kf = K factor or K = kf factor-1
conversion factor permeability to kf
t °C ?=1000 kg m-3 ?=1050 kg m-3 ?=1100 kg m-3 ?=1200 kg m-3  
0 5.51 106 5.79 106 6.06 106 6.61 106 m-1 s-1 
5 6.47 106 6.79 106

7.12 106

7.76 106 m-1 s-1 
10 7.49 106

7.86 106

 8.24 106 8.99 106 m-1 s-1 
15 8.57 106 9.00 106 9.43 106 1.03 107 m-1 s-1 
20

9.71 106

 1.02 107 1.07 107 1.17 107 m-1 s-1 
25 1.09 107 1.15 107 1.20 107 1.31 107 m-1 s-1 
30 1.22 107 1.28 107 1.34 107 1.46 107 m-1 s-1 
typical permeabilities for different rocks
(Freeze & Cherry, 1979)
rock type from to  
gravel 10-7 10-10 m2
sand 10-9 10-13 m2
silty sand 10-10 10-14 m2
silt, Loess 10-12 10-16 m2
tilll 10-13 10-19 m2
marine clay, non weathered. 10-16 10-19 m2
schist 10-16 10-20 m2
non fractured metamorphites and plutonites 10-17 10-20 m2
sandstone 10-13 10-17 m2
limestone, dolomite 10-13 10-16 m2
fractured metamorphites and plutonites 10-11 10-15 m2
porous basalt 10-9 10-14 m2
karst 10-9 10-13 m2
conversion to Darcy Permeabilities are sometimes given in Darcy ( D = cm2 cP atm-1 s-1)
The dimensionless conversion factor is 9.8692 10-13
K [m2 ] = K [D] * 9.8692 10-13

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