Page 89 - Air and Gas Drilling Manual
P. 89
Chapter 3: Downhole Equipment 3-17
The above table also shows an insert rock bit comparison chart for four
manufacturers (second through fifth columns). Feature 2 on all the bit manufacturers
charts shows the insert bits designed for air drilling operations. Although the
comparison chart shows insert tri-cone drill bits, the sealed roller bearing and sealed
journal bearing bits are also often selected for air and gas drilling operations.
It should be noted that single cone drill bits and air hammer bits are not
presently classified in accordance to the IADC code system.
3.3 Bottomhole Assembly
Figure 3-16 shows a typical bottomhole assembly (BHA) for a direct circulation
rotary drilling operation. The BHA is the section of the drill string below the drill
pipe (see Figure 3-1). This section of the drill string is the most rigid length of the
string. It is this section of the drill string that determines how much weight can be
placed on the drill bit and how “straight” a vertical borehole will be drilled with the
drill string.
Figure 3-16: Typical bottomhole assembly for direct circulation rotary drilling
operations.
