Page 10 - Air and Gas Drilling Manual

e avo
= openhole outer wall absolute surface roughness, ft
e oh
= absolute surface roughness of commercial pipe, 0.00015 ft
e p = average absolute surface roughness of the annulus, ft xi List of Symbols
f = Fanning friction factor
F = axial tension force (or load), lb
F a = maximum allowable design axial tension force, lb
f ac = Fanning friction factor for flow in the cased section of the annulus
f b = Fanning friction factor for the blooey line
F c = hoisting capacity of rotary drill rig, lb
FS = factor of safety
f sr = Fanning friction factor for flow in the surface return flow line
F y = drill pipe tension force to produce material yield, lb
g = acceleration of gravity, 32.2 ft/sec 2
H = total depth of borehole, ft
h = reference depth, ft
HP b = drive shaft horsepower developed at any drive shaft speed, hp
k = ratio of specific heats for the gas (for air k = 1.4 and for natural gas
k = 1.28)
K a = average drilling rate, ft/hr
K b = buoyancy factor
KE = kinetic energy per unit volume, ft-lb/ft 3
KE a = kinetic energy per unit volume for air drilling, ft-lb/ft 3
KE ai = kinetic energy per unit volume of the gas above the drill bit inside the drill
pipe, ft-lb/ft 3
KE bh = kinetic energy per unit volume at the bottom of the borehole in the annulus,
ft-lb/ft 3
KE m = kinetic energy per unit volume for drilling mud, ft-lb/ft 3
KE sfake = kinetic energy per unit volume in the annulus, ft-lb/ft 3
K t = minor loss factor for the T turn at the top of the annulus