Page 100 - Air and Gas Drilling Manual

3-28 Air and Gas Drilling Manual
the very limber drill pipe. Their use as transitional stiffness elements reduces the
mechanical failures in the bottom drill pipe elements of the drill string. Heavy-
weight drill pipe is also used in directional drilling operations where drill collars can
be replaced by the heavy-weight pipe. Using heavy-weight drill pipe in place of drill
collars reduces the rotary torque and drag, and increases directional control.
3.4.3 Drill Rod
Small rotary drilling rigs often use drill rod as a drill pipe substitute. Drill rod
is used in mining, environmental, and geotechnical drilling operations. These rods
are available in 2 ft, 5 ft, and 10 ft lengths. They are used in both mud (or water)
and air drilling operations. There are two types of drill rods, wireline drill rods, and
conventional drill rods.
Wireline Drill Rod
Figure 3-23 shows a schematic profile of wireline drill rod. This type of drill
rod has no change in inside diameter at the connections (smooth bore over entire
length). This allows wireline coring to proceed through the drill rod. The outside
of the rod is also smooth with no increase in outside diameter at the tool joints.
The connections are not API but are shouldered connections which give adequate
strength in shallow rotary drilling operations.

Figure 3-23: Wireline drill rod schematic profile of rod body, and box and pin
connections (courtesy Boart Longyear Incorporated).

Table 3-4 gives dimensions and mechanical properties for AQ, BQ, NQ, and
HMQ wireline drill rod. Wireline drill rod is available in 5 ft and 10 ft lengths (and
custom lengths). This drill rod type is used in the rotary drilling operations where
core retrieval is the principal objective. These are usually shallow small diameter
boreholes. This drill rod type was originally developed for mining drilling
operations but is now used extensively in environmental and geotechnical drilling
operations.