Page 28 - Air and Gas Drilling Manual

Chapter 1: Introduction 1-5
Single rigs can be fitted with either an on-board air compressor, or an on-board
mud pump. Some of these rigs can accommodate both subsystems. These rigs have
either a dedicated prime mover on the rig deck, or have a power-take-off system
which allows utilization of the truck motor as a prime mover for the drilling rig
equipment (when the truck is stationary). These small drilling rigs provide axial
force to the drill bit through the drill string via a chain or cable actuated pull-down
system, or hydraulic pull-down system. A pull-down system transfers a portion of
the weight of the rig to the top of the drill string and then to the drill bit. The
torque and rotation at the top of the drill string is provided by a hydraulic tophead
drive (similar to power swivel systems used on larger drilling rigs) which is moved
up and down the mast (on a track) by the chain drive pull-down system. Many of
these small single drilling rigs are capable of drilling with their masts at a 45˚ angle
to the vertical. The prime mover for these rigs is usually diesel fueled.
Figure 1-4 shows a typical double drilling rig. Such drilling rigs are also
mobile and can be self-propelled or trailer mounted. Figure 1-5 shows the schematic
of a self-propelled double drilling rig.

Figure 1-4: Typical trailer mounted drilling rig (courtesy of George E. Failing Company).
The trailer mounted drilling rig in Figure 1-4 is a George E. Failing Company
SS-40. These double rigs have the capability to drill to depths of approximately
10,000 ft and are used for oil and gas drilling operations, geothermal drilling
operations, deep mining and geotechnical drilling operations, and water wells.
Double rigs typically use Range 2 drill collars or drill pipe. These rigs are fitted