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Shale Shaker
International
Equipment
Shale Shakers
The shale shaker is primary and probably most
important device on the rig for removing drilled solids from the mud. This
vibrating sieve is simple in concept, but a bit more complicated to use
efficiently.
A wire-cloth screen vibrates while the drilling
fluid flows on top of it. The liquid phase of the mud and solids smaller
than the wire mesh pass through the screen, while larger solids are
retained on the screen and eventually fall off the back of the device and
are discarded.
Obviously, smaller openings in the screen
clean more solids from the whole mud, but there is a corresponding decrease
in flow rate per unit area of wire cloth. Hence, the drilling crew should
seek to run the screens (as the wire cloth is called), as fine as possible,
without dumping whole mud off the back of the shaker.
Where it was once common for drilling rigs
to have only one or two shale shakers, modern high-efficiency rigs are
often fitted with four or more shakers, thus giving more area of wire cloth
to use, and giving the crew the flexibility to run increasingly fine
screens.
Shale shakers are a device that removes
drill cuttings from the drilling fluid while circulating and drilling.
There are many different designs and research into the best design is
constantly ongoing since solids control is vital in keeping down costs
associated with the drilling fluid.
Desander
A hydrocyclone
device that removes large drill solids from the whole mud system. The desander should be located downstream of the shale
shakers and degassers, but before the desilters
or mud cleaners. A volume of mud is pumped into the wide upper section of
the hydrocylone at an angle roughly tangent to
its circumference. As the mud flows around and gradually down the inside of
the cone shape, solids are separated from the liquid by centrifugal forces.
The solids continue around and down until they exit the bottom of the hydrocyclone (along with small amounts of liquid) and
are discarded.
The cleaner and lighter density liquid mud
travels up through a vortex in the center of the hydrocyclone,
exits through piping at the top of the hydrocyclone
and is then routed to the mud tanks and the next mud-cleaning device,
usually a desilter. Various size desander and desilter cones
are functionally identical, with the size of the cone determining the size
of particles the device removes from the mud system.
Desilter
A hydrocyclone
much like a desander except that its design
incorporates a greater number of smaller cones. As with the desander, its purpose is to remove unwanted solids from
the mud system. The smaller cones allow the desilter
to efficiently remove smaller diameter drill solids than a desander does. For that reason, the desilter
is located downstream from the desander in the
surface mud system.
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