Page 141 - Drilling Technology in Nontechnical Language

132 Drilling Technology in Nontechnical Language Second Edition

So far, the mud has been processed by the shale shakers, sandtrap,
desanders, and desilters—each stage removing progressively finer particles.

If it is felt necessary to remove even smaller particles, a centrifuge (or
several centrifuges) may be used. The cleaned mud ends up in the mud
pump suction tank, from where the mud pumps circulate mud around the
well again.

Hoisting equipment

The most visible part of a drilling rig is the derrick, or the mast that is
around 140 ft taller than the drill floor. The derrick has a set of sheaves on

the top, over which steel rope can pass.
The sheaves at the top of the derrick are called the crown block. These
sheaves support loops of steel rope that pass through sheaves on the
traveling block.
The drawworks drum is usually powered by one or more DC electric
motors. As the drawworks reel in the block line onto the drum, the
traveling block moves up the derrick (fig. 5–18). The drawworks drum is

also controlled by a braking system. To lower the traveling block, the brake
is released, and the weight of the traveling block and any load under it will
move the block downwards and unreel rope from the drum. The brake is
used to control the speed of movement. By this means, the rig can pick up

or lower pipe in the well with very fine control of movement and force.
At the deadline end of the block line is a sensator, or a tool that
measures physical force and transmits this information to an instrument
or control system. The sensator measures the pull on the wire rope. This
is connected to a large dial with hands that indicate the weight of traveling
block and any load held under it. This instrument, called the weight
indicator, must be calibrated for the number of times that the line loops
around the crown block.
The weight indicator is one of the most important instruments that the
driller has in front of him at his controls. Every operation involving control
of the traveling block is monitored on the weight indicator, which is why it
is so large. It is the largest instrument face on the panel.

_Devereux_Book.indb 132 1/16/12 2:09 PM