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Mud flow indicators are used to help detect a kick more
quickly. The more commonly used devices are somewhat similar
to the pit level indicators. A paddle-type fluid level sensor is used
in the flow line. In addition, a pump-stroke counter is used to sense
the flow-rate into the well. A panel on the rig floor displays the
flow rate into and out of the well. If the rates are appreciably
different, a gain or loss warning will be given.
While making a trip, circulation is stopped and a significant
volume of pipe is removed from the hole. Thus, to keep the hole
full, mud must be pumped into the hole to replace the volume of
the pipe removed. Kick detection during tripping operations is
accomplished through the use of a hole fill-up indicator. The
purpose of the hole fill-up indicator is to measure accurately the
mud volume required to fill the hole. If the volume required to fill
the hole is less than the volume of the pipe removed, the kick may
be in progress.
Small trip tanks provide the best means of monitoring hole
fill-up volume. Trip tanks usually hold 10 to 15 bbl and have 1-bbl
gauge markets. Two alternative trip tank arrangements are
realized. With either arrangement, the hole is maintained full as
pipe is withdrawn from the well. Periodically, the trip tank is
refilled using the mud pump. The top of the gravity feed type trip
tank must be slightly lower than the bell nipple to prevent mud
from being lost to the flow line. The required fill-up volume is
determined by periodically checking the fluid level in the trip tank.
When a trip tank is not installed on the rig, hole fill-up volume
should be determined by counting pump strokes each time the hole
is filled. The level in one of the active pits should not be used since
the active pits are normally too large to provide sufficient
accuracy.
The flow of fluid from the well caused by a kick is stopped
by use of special pack-off devices called blowout preventers
(BOPs). Multiple BOPs used in a series are referred to collectively
as a BOP stack. The BOP must be capable of terminating the flow

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