Solids Control –Hydrocyclones

Hydrocyclones are cone shaped designed to take out smaller particles–Desanders 74-45 microns–Desilters 35-15 microns–Micro Cones 7-9 microns

•A centrifugal pump feeds a high-volume mud through a tangential opening into the large end of the funnel-shaped hydroclone.
•When the proper amount of head (pressure) is used, this results in a whirling of the fluid much like the motion of a water spout, tornado or cyclone, expelling wet, higher mass solids out the open bottom while returning the liquid through the top of the hydroclone.
•Thus, all hydroclones operate in a similar manner, whether they are used as desanders, desilters or clay ejectors.
•Head is related to pressure as follows: –Head (ft) = Pressure (psi)/[.052 x mud weight (lb/gal)] –Most hydrocyclones designed for about 75 ft of head at the inlet manifold
•Capacity is related to hydroclone size, so more smaller hydroclones are required for a given volume than larger ones.
•An example of hydroclone removal efficiency, showing the cut and D10-D50-D90values for typical 3-, 4-and 6-in. hydroclones, is depicted in the graph opposite.
•Desanders usually are 6-in. hydroclones or larger, with two 12-in. hydroclones being common. •Desilters use 4-to 6-in. hydroclones, with 12 or more 4-in. hydroclones being common.
•Clay ejectors or microclones use 2-in. hydroclones, with 20, 2-in. hydroclones being common. •The hydroclone discharge, or underflow, must be evaluated to ensure that the hydroclone is operating efficiently.
•The discharge should be in the form of a fine spray, with a slight suction felt at its center. •When drilling a large diameter hole at high ROP, the feed may become overloaded with solids and result in a rope-type discharge. –At times, this may have to be tolerated, since shutting the unit down would be worse.