STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

Air and Gas Drilling 855
Table 4-107
Constants C1, C2 and C3 for Various Surface
Locations Above Sea Level
Surface Loution
A b o 5.6 Level
(ft) c1 C2 c3
0 6.610 28.83 1.628 XIO 6
2,Ooo 5.873 30.59 1.446 x IO
4.000 5.207 32.48 1.28' x IO
6,000 4.612 34.52 1,136 x IO
8.m 4.080 36.70 1.00.5 x 10-b
10.000 3.605 39.04 0.8878~ IO
various surface locations above sea level. Also Table 4-109 gives atmospheric
pressure, temperature and specific weight of air for various surface locations
above sea level.
Example
Find the minimum Q (actual cfm) for an air drilling operation at a surface
location of 6,000 ft above sea level. Drilling is to begin at 8,500 ft of depth
and continue to 10,000 ft. The borehole, from top to bottom, has nearly a
uniform inside diameter of slightly larger than 8+ in. The bit to be used to drill
the interval is Sq in. The outside diameter of drill pipe is 49 in. The expected
drilling rate is 60 ft/hr. The geothermal gradient will be taken to be 0.01 OF/ft.
To obtain the governing minimum Q for the interval to be drilled, Equation
4-122 must be solved at 10,000 ft of depth. Since the drilling location is at a
surface location of 6,000 ft above sea level, from Table 4-107, we have
C, = 4.612
C, = 34.52
C, = 1.136 x
Table 4-108
Atmosphere at Elevations Above Sea Level
SUM Loatlon
Aborn 5.. Lwol Proowro Tomporntun Specltlc Weight
(11) (P.1) (-7 (wnq
0 14.6% 59.00 0,0765
2.000 13.662 51.87 0.0721
4 .OOo 12.685 44.74 0.0679
6.000 1 I .769 37.60 0.0639
8 .oOO 10.9 I I 30.47 CY.0601
1o.OOo IO. 108 23.36 0.0565