Page 325 - Air and Gas Drilling Manual

8-8 Air and Gas Drilling Manual
drill string will be assumed to have a uniform dimension of a 4 1/2 inch outside
diameter from top to bottom.

Figure 8-4: Illustrative Example 8.1 casing and openhole well geometric configuration.
In order to be able to calculate air drilling conditions at other surface elevations
above sea level, all calculations to obtain values like the minimum volumetric flow
rate are carried out for a baseline sea level atmosphere. For these calculations and
most of those in this treatise the baseline sea level atmosphere is the API standard
conditions (see Chapter 4). These conditions are a pressure of 14.696 psia and a
temperature of 60˚F. Thus, the pressure of the gas (in this case air) that flows into
the compressor, P at, is
p = 14 696 psia
.
at
P at = p 144
at
2
,
P at = 2 116 lb/ft abs
where p at is atmospheric pressure (psia),
2
P at is atmospheric pressure (lb/ft , abs).