Page 15 - Air and Gas Drilling Manual

xvi List of Symbols
= fixed compression ratio
r st
= universal gas constant, 1,545.4 ft-lb/lb-mole-°R
R u
3
s = displacement, in
S g = specific gravity of the particular gas used
S s = specific gravity of the solid rock cuttings
S wf = specific gravity of the formation water
T = absolute temperature at any position in the annulus, °R
T = applied torque to the top of the drill string, ft-lb
t = vane thickness, ft
T at = absolute atmospheric temperature, °R
t at = atmospheric temperature, °F
T av = average temperature of the borehole over the depth interval, °R
T avc = average absolute over the depth to the bottom of the cased section of the
borehole, °R

T avo = average temperature of the openhole section of the borehole, °R
T bh = bottomhole temperature, R
T c = absolute temperature at the bottom of the casing, °R
T g = absolute gas temperature, °R

t h = geothermal temperature at depth, °F
T i = input gas temperature, °R (K)
Torque b = torque developed by the motor at any drive shaft speed, ft-lb
Torque sb = stall torque of the drive shaft, ft-lb
Torque sr = stall torque of the turbine motor, ft-lb
T pl = absolute pipeline temperature, °R
t pl = pipeline temperature, °F
T r = absolute reference temperature, °R
t r = reference temperature, °F
V = average velocity in the annulus, ft/sec