Page 137 - Drilling Technology in Nontechnical Language

128 Drilling Technology in Nontechnical Language Second Edition

2. An ultrasonic detector is positioned above the tank. A sound
signal is generated, and the time for the signal to bounce off the
mud surface and return to the detector is measured. Knowing the
speed of sound in air, the distance from a known point (the sound
generator) to the detector via the mud surface can be calculated,
and this can be converted to a volume for that particular tank.

The driller has an instrument, called the pit volume totalizer, that can
display the volume in any particular tank and can also add up all of the
surface active volumes so that any change in the total surface volume may
be detected. The PVT also includes alarms that can be set so that changes
beyond a set amount lost or gained will cause an alarm to sound.

Fig. 5–14. Mud tank with oat-type level indicator

Photo courtesy of Schlumberger.

Solids control equipment

When the drilling fluid leaves the annulus at surface during drilling,
it contains rock particles of various sizes that have entered the mud either
at the drill bit or after falling off the wall of the hole. If the solids control

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