Page 138 - Drilling Technology in Nontechnical Language

Chapter 5 – RIG SELECTION AND RIG EQUIPMENT 129

equipment does not work efficiently, some of these rock particles can be

pumped back down the well, and these become ground up even smaller
by mechanical action in the well. The smaller they are, the harder it is
to remove these particles from the mud when it returns to the surface.
Smaller particles also have a greater ability to negatively affect the physical
properties of the mud, which then will need expensive chemical treatments

to restore the desirable properties to drill efficiently.
The solids control equipment consists of a series of items to remove

progressively smaller rock particles. The first and most important item of
equipment that the mud passes through is called a shale shaker. The shale

shakers are basically a set of vibrating mesh screens that filter out large
rock particles and allow the liquid mud to fall through the screens to a
tank below (fig. 5–15). These vibrating screens are designed so that solids

filtered out of the mud move along the screen to the edge, where they fall
off into a chute for disposal. Sometimes a screen will break or split or
develop a hole, and then some of the drilled cuttings fall through with the
mud into the tank below. It is very important that the drill crews are alert to
damaged shale shaker screens. If large amounts of rock bypass the shakers,
this will overload the other solids control equipment and cause problems
all the way through the system. The screens are replaced if damaged.

Fig. 5–15. Shale shakers

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