Page 16 - Air and Gas Drilling Manual

xvii List of Symbols
V ai
= velocity of the gas at the bottom of the borehole in the annulus, ft/sec
V bh
= critical concentration velocity, ft/sec
V c = velocity of the gas above the drill bit inside the drill pipe, ft/sec
V dci = approximate velocity of compressed air inside the drill collars, ft/sec
V f = average velocity of the fluid, ft/sec
= total velocity of the fluid, ft/sec
V ml
V n = velocity of the gas exiting the nozzle, ft/sec
Vol c = compressed volume of the compressed air in the drill collars after the stop,
ft 3
V sfa = average velocity of foam exiting the cased annulus and starts into the Tee,
ft/sec
V sfake = average velocity of foam above the drill collar annulus section flowing
around the drill pipe body, ft/sec
V sfbp = average velocity of foam upstream of the back pressure valve, ft/sec
V sr = average velocity of the aerated drilling fluid exiting the end of the surface
return flow line, ft/sec
V t = terminal velocity of the rock cuttings particle, ft/sec
V Tee = approximate velocity of foam flow downstream of the Tee and valves,
ft/sec
V tl = terminal velocity for laminar flow conditions, ft/sec
w c = weight per unit length of drill collars, lb/ft
w p = weight per unit length of drill pipe, lb/ft
.
w = weigh rate of flow through the compressor, lb/sec (N/sec)
.
w f = total weight of fuel consumption per hour, lb/hr
.
w fw = weight rate of flow of formation water, lb/sec
.
w g = weigh rate of flow of the gas, lb/sec
.
w iw = weight rate of flow of injected water , lb/sec