Page 66 - Hydrocarbon

Drilling Engineering 53

crown block

drill pipes

platform
cable
travelling block
& hook
swivel head

kelly

vibrating screen rotary table
slush pump engines
mud ditch derrick floor
ground level
mud suction pit
blow-out
preventer

Figure 4.6 The basic rotary rig.

However, in practice, onshore and offshore drilling units are often quite
different in terms of technology and degree of automatisation. This is largely driven
by rig availability, costs and safety considerations, and will be explained in more
detail in the following text.
We will now consider the rotary rig in operation, visiting all elements of the
system. The type of rig operation described first is now found mainly in low-cost
onshore areas. For complicated, more expensive wells, older rigs have usually been
upgraded to include a top drive system and automated pipe handling as described later in
this section. New rigs are usually built with this equipment as standard.

4.3.1. Drill bits

The most frequently used bit types are the roller cone or rock bit and the
polycrystalline diamond compact bit or PDC bit (Figure 4.7).