Page 29 - Oil and Gas Production Handbook An Introduction to Oil and Gas Production

A special high density mud called Kill Fluid is used to shut down a well for
workover.

Mud is recirculated. Coarse rock shales are separated in a shale shaker
before it is passed though finer filters and recalibrated with new additives
before returning to the mud holding tanks

3.4 The well

When the well has been drilled, it must be completed. Completing a well
consists of a number of steps, such as installing the well casing, completion,
installing the wellhead, and installing lifting equipment or treating the
formation should that be required.

3.4.1 Well casing
Installing the well casing
is an important part of the
drilling and completion
process. Well casing
consists of a series of
metal tubes installed in
the freshly drilled hole.
Casing serves to
strengthen the sides of
the well hole, ensure that
no oil or natural gas
seeps out as it is brought
to the surface, and to
keep other fluids or gases
from seeping into the
formation through the
well. A good deal of planning is necessary to ensure that the right casing for
each well is installed. Types of casing used depend on the subsurface
characteristics of the well, including the diameter of the well (which is
dependent on the size of the drill bit used) and the pressures and
temperatures experienced. In most wells, the diameter of the well hole
decreases the deeper it is drilled, leading to a type of conical shape that
must be taken into account when installing casing. The casing is normally
cemented in place. Ill: wikipedia.org

There are five different types of well casing. They include:

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