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Equipment in Mud Circulating Systems 11

1.4 CONTAMINANT-REMOVAL EQUIPMENT
The contaminant-removal equipment is often called solid-removal
equipment because it is mostly used for removing drilling cuttings in the
mud returned from the borehole. A primary solid-removal equipment
should include shale shakers, a degasser, a desander, a desilter, and a
decanting centrifuge. All of these parts are installed on top of the mud
tanks. As shown in Figure 1.12 (Moore, 1986), the order of operation is
shale shakers, degasser, desander, desilter, and centrifuge.
The term shale shaker is used in mud drilling to cover all of the
devices that in other industries might be differentiated as shaking
screens, vibrating screens, and oscillating screens. All three of these
types are used in the oil and gas industry, although most of them would
probably fall into the vibrating screen classification. Figure 1.13 shows
a shale shaker. Several factors affect the efficiency of shale shakers,
including mud properties, screen mesh, vibrating frequency, and geome-
try of design. The particle-size separation made by a shale shaker screen
is not simply that all particles larger than the stated screen mesh are

Borehole

Mud
Pumps

Shale
Shaker

Cuttings
Removal
Sand Trap
underneath Degasser
Shale Shaker Centrifuge
Overflow

Desander Desilter
Underflow Underflow
Figure 1.12 The solid-removal equipment.