Page 248 - Shale Shakers Drilling Fluid Systems
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230 SHALE SHAKERS AND DRILLING FLUID SYSTEMS
The intent of this rule is to provide some chased instead of valves. When the desilter
guideline so that a backflow will exist. As long pump is on, the system is being desilted and
as there is more fluid processed than is en- there should be no question concerning routing.
tering the compartment, except for the back- All systems, whether dispersed, nondispersed,
flow, all of the fluid entering the compartment polymer, water-based, oil-based, synthetic, or
will be processed. salt, will need the same sequential treatment by
the removal equipment.
27. If Rules 21, 25, and 26 are applicable and are
followed, equalizing flow between compartments 32. In a properly designed system, solids control
will be in the reverse (or upstream) direction. devices should not overflow into mud ditches.
Backflow confirms that all mud entering the Many drilling fluid systems have a square chan-
compartment is being processed.
nel (approximately 2' x 2') along the top of
In normal drilling operations Rules 21, 25, and one side of the tanks. Metal plate openings
26 are applicable. (ditches) are provided so that drilling fluid can
bypass compartments. As drilling fluid drops
28. Mud should never be pumped from one removal from a ditch opening into the top of the fluid
compartment to another except through solids in the tank, air is entrained. These ditches can
removal equipment. be useful for completion fluids and other spe-
ciality conditions, however, their use in drill-
The intent of this rule is to ensure that all ing operations may result in drilling fluid by-
drilling fluid is processed in an orderly fash- passing solids removal equipment.
ion. Drilling fluid should not bypass any
solids removal equipment or be pumped up-
stream from a suction compartment. 33. Exception to rule 32: Based on field experience,
mud foaming problems can be reduced by rout-
ing the overflow of a desander or desilter into
29. Mud should never enter any removal compart- a mud ditch for a horizontal distance of about
ment from outside the removal section to
feed mud guns, mixers, or the eductor jet of a ten feet before the fluid enters its discharge
compartment to allow entrained air to break
vacuum degasser.
out. If this is done, ensure that the fluid rout-
When a system is designed, the equipment is ing is correct.
set up to treat a certain quantity of drilling
Flowing drilling fluid down a ditch allows the
fluid. Increasing the flow rate demand by re- fluid/air interface to expose more of the en-
turning drilling fluid from downstream usually
results in an inefficient removal system. trained air to the surface. Sometimes, how-
ever, air does not break-out in this distance
and more air is entrained as the fluid drops
30. The power mud for the eductor jet for a vacuum into the active system. Obviously, experts have
degasser should come from the degasser dis- many differing opinions concerning ditches.
charge compartment.
The drilling fluid to pull the fluid from the 34. All mud material additions should be made af-
vacuum degasser usually comes from a cen- ter the Removal Section. All removal, including
trifugal pump. This fluid must be degassed. all centrifuging, must be finished before the mud
The fluid in the degasser discharge compart- material addition begins.
ment is pumped through the eductor and re-
turns to the same compartment. This will not This rule is a result of problems which in-
interfere with solids removal efficiency. curred when adding a weighting agent up-
stream from mud cleaners (or pumping fresh
weighting agent upstream through mud guns).
31. Single purpose pumps are necessary in the Re- API barite allows 3% weight larger than 200
moval Section to ensure proper fluid routing. mesh, most of which will be removed by a mud
One suction and one discharge should be used. cleaner. All undesirables must be removed be-
Suction and discharges should not be manifolded.
fore new products are added. One exception to
Manifolding ruins more good drilling fluid sys- this rule is the addition of flocculents, or other
tems than just about any other single design. materials, to aid removal of drilled solids.
For this reason, dedicated pumps should be
used. Since multiple leaky valves will confuse 35. Mud foaming problems can also be reduced by
proper fluid routing, a standby pump be pur- using a non-air-entraining mud mixing hopper.
