Page 416 - Air and Gas Drilling Manual

9-20 Air and Gas Drilling Manual
w ˙
Q
g
ln
P m T av w ˙ s H P bh P bh P e H Q m (9-9)
g g
T g P e
Illustrative Example 9.2 below describes the implementation of the basic
planning step No. 9 in Section 9.1. The non-friction solution is applied to a deep
well example. This is only done as a demonstration. It is instructive to compare
the non-friction solution results to the full friction solutions results that will be
obtained later in this chapter. The approximate values for the volumetric flow rates
of the incompressible fluid (drilling mud) and the compressible gas (air) can be used
as a initial values for the complicated trial and error solution required for the full
friction solution.
Illustrative Example 9.2 Using the non-friction method and the given data
and the results obtained in Illustrative Example 9.1, determine the approximate
volumetric flow rate of air required for the incompressible drilling fluid (drilling
mud) volumetric flow rate of approximately 191 gal/min while drilling at 10,000 ft.
Table 4-1 gives an average atmospheric pressure of 12.685 psia for a surface
location of 4,000 ft above sea level (mid latitudes North America) (also see
Appendix D). The actual atmospheric pressure for the air at the drilling location
(that will be used by the compressor), P at, is
p at 12 685 psia
.
P at p 144
at
2
,
.
P 1 826 6 lb/ft abs
at
The actual atmospheric temperature of the air at the drilling location (that will be
used by the compressor), T at, is
t at 60˚F

T t 459 67
.
at at
T at 519 67.˚R

Thus, P g and T g become
2
.
,
P g P at 1 826 6 lb/ft abs
T T 519 67.˚R
g at