STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

854 Drilling and Well Completions
cuttings to the surface. This initial calculation depends principally upon the
borehole geometry and the drilling rate.
The minimum volumetric flowrate Q (actual cfm) can be obtained from [61]
(4- 122)
and
a=
SQ + C,KD:
53.352
(4-123)
(4-124)
where D, = inside diameter of borehole in ft
D = outside diameter of drill pipe in ft
A' = specific gravity of gas (air is 1.0)
TS = surface atmospheric temperature in OR
Tv = average temperature of flow in annulus in OR
= geothermal gradient in O F per ft
K = drilling rate in ft/hr
Vmin = equivalent minimum velocity of standard air for removal of cuttings
(Vmin = 3000 ft/min)
h = hole depth in ft
The constants C,, C,, C, are
(4-125)
n
- (62.2)( 2.7)
4 c, =
(4-126)
c, =
(4- 127)
where T, = temperature at sea level standard atmospheric conditions (i.e., 520OR)
P, = pressure at sea level standard atmospheric conditions (i.e., 2116.8
lb/ft2)
Thus, C,, C, and C, are related to the actual atmospheric surface conditions
where drilling is taking place. Table 4107 gives the values of C,, C, and C, for