Page 19 - Air and Gas Drilling Manual

xx List of Symbols
γ sfa
3
= specific weigh of foam upstream of the back pressure valve, lb/ft
γ sfbp
3
= approximate specific weight at the Tee, lb/ft
γ Tee = specific weigh of foam exiting the cased annulus and starts into the Tee, lb/ft 3
3
γ w = specific weight of the incompressible fluid, lb/ft
κ = penetration rate, ft/sec
κ max = actual sustainable maximum drilling rate, ft/hr
2
2
µ e = effective absolute viscosity, lb-sec/ft (n-sec/m )
µ g = absolute viscosity of the air at atmospheric conditions, lb-sec/ft 2
µ m = absolute viscosity of the drilling mud, cps
2
µ mp = absolute plastic viscosity of the drilling mud, lb-sec/ft
µ sf = absolute viscosity of the stable foam, lb-sec/ft 2
µ sfa = absolute viscosity of foam exiting the cased annulus and starts into the Tee, lb-

sec/ft 2
µ sfbp = absolute viscosity of the foam just upstream of the back pressure valve, lb-
sec/ft 2
µ w = absolute viscosity of the water (and surfactant), lb-sec/ft 2
2
ν = kinematic viscosity of the drilling fluid, ft /sec
2
ν avi = kinematic viscosity of mixture entering the drill string, ft /sec
2
ν el = effective kinematic viscosity for laminar conditions, ft /sec
2
ν g = kinematic viscosity of the gas, ft /sec
2
ν gi = kinematic viscosity of gas entering the drill string, ft /sec
2
ν m = kinematic viscosity of the drilling mud, ft /sec
ν sfa = kinematic viscosity of foam exiting the cased annulus and starts into the Tee,
2
ft /sec
2
ν sfbp = kinematic viscosity of foam upstream of the back pressure valve, ft /sec