BAKER HUGHES - Drilling Fluids Reference Manual

MECHANICAL SOLIDS CONTROL
Desilters are hydroclones which are normally 4 in. in diameter and will process 50 to 80 gal of
fluid per minute per cone depending on manufacturer. Feed head requirements range from 75 to 96
ft with the most common requirement being 75 ft. Desilters with a spray discharge will make a 16-
to 18-micron median cut on low-gravity solids. A sufficient number of cones should be provided to
process 1.25 to 1.5 times the circulating rate for maximum efficiency.
It is most important that desilters be employed at the start of an operation and run almost
continuously until a weighted drilling fluid is required. If desilting is delayed or utilized only parttime,
the recycled drilled solids will rapidly degrade into particle sizes too small to be removed by
the desilter.
The general operating parameters for hydrocyclones is presented in Table 10 – 4 as follows:
Press
(psi)
2" 4" 6" 12"
Head Vol Press Head Vol Press Head Vol Press Head
(ft) (gpm) (psi) (ft) (gpm) (psi) (ft) (gpm) (psi) (ft)
Vol
(gpm)
35 75 20 35 75 60 35 75 100 35 75 500
Table 10 - 4 Recommended Hydrocyclone Feed Head Requirements (Pressures based
on 9 lbm/gal fluid)
The quantity of solids removed from an unweighted system by a hydrocyclone can be calculated as
follows.
W S = 97(D μ – 8.33)(Q µ )
where,
Ws = lb solids removed per hour per cone
Dµ= density of underflow, lb m /gal
Qµ = underflow rate, gal/min.
Smaller diameter hydrocyclones (usually 2 inches in diameter) have been used for barite salvage.
Under ideal conditions, these cones will make a D-50 cut on barite in the 4- to 6-micron range and
a 7- to 10-micron out on low-gravity solids. Barite recovery efficiency is less than that obtained
with a centrifuge which should give D-95 cut in the 4- to 6-micro range.
Figure 10-4 illustrates approximate performance curves for various diameter hydrocyclones. These
curves are for low-gravity solids in unweighted drilling fluids.
BAKER HUGHES DRILLING FLUIDS
REVISION 2006 10-13
REFERENCE MANUAL