Page 201 - Air and gas Drilling Field Guide 3rd Edition

192 CHAPTER 8 Air, Gas, and Unstable Foam Drilling

13
1
(152.4 m)of6 4 = -in (158.8 mm)by 2 = -in (71.4 mm) drill collars above the
16
1
drill bit and API 4 2 = -in (190.5 mm), 16.60-lb/ft (7.62 kg/m) nominal, IEU-S135,
NC46 to the surface. The tool joints of this drill pipe have an outside diameter
1
3
of 6 4 = in (154.8 mm) and an inner diameter of 2 4 = in (69.9 mm). The surface
location of the drilling site is 4000 ft (1219 m) above sea level in midlatitudes
of North America (see Table 5-1 and Appendix B). Also, the regional geothermal
gradient is approximately 0.01 F/ft (0.018 C ). Figure 8.5 shows a schematic of

this illustrative example well geometry.
The anticipated drilling rate of penetrations in a sandstone and limestone
sequence is approximately 60 ft/hr (18.3 m/hr). The blooey line for this drilling oper-
ation is a single horizontal section of casing that runs 200 ft (61 m) from just above
5
the BOP stack to the burn pit. The casing used for the blooey line is API 8 8 = -in
(219 mm), 24.00-lb/ft (10.5 kg/m) nominal, Grade J-55, casing. The inside diameter
of this casing is 8.097 in (205.7 mm). Two gate valves are in the blooey line at the end
9
=
of the line attached to the BOP stack. These valves have an inside diameter of 7 16
in (192 mm). The objective of this illustrative example is to show how Appendix G
can be used to obtain an initial approximation for the minimum volumetric flow
rate to clean the well bore while drilling at 10,000 ft (3048 m).
The graphs in Appendix G were developed using a simplified model. This
model assumes a uniform borehole inside diameter, top to bottom (assumed to
be the same as drill bit diameter). All minor losses were ignored. The well is
assumed to have casing in the upper two-thirds of the depth and an open hole
in the bottom one-third of the well. The annulus is described by the inside
diameter of the borehole and the outside diameter of the drill pipe.
Figure G-13 is the appropriate figure in Appendix G that will best approxi-
mate the drilling geometry in Illustrative Example 8.1. For a rate of penetration
of 60 ft/hr, the approximate minimum volumetric flow rate is 1588.8 scfm
(749.8 standard liters/sec).

USCS Units
Specific Weight of Air at API Standard Conditions
At API standard conditions, the atmospheric pressure is
p st ¼ 14:696 psia
P st ¼ p st 144
2
P st ¼ 2116:0lb=ft abs;
2
where p st is atmospheric pressure (psia) and P st is atmospheric pressure (lb/ft abs).
At API standard conditions, the atmospheric temperature is
o
t st ¼ 60 F
T st ¼ t st þ 459:67
o
T st ¼ 519:67 R;