BAKER HUGHES - Drilling Fluids Reference Manual

MECHANICAL SOLIDS CONTROL
then you would only be removing 45.5 lb of solids for each bbl removed. If you would condense
these solids by use of a centrifuge to 40% by volume solids, then for each bbl hauled off, 363.9 lb
of solids would be removed. To achieve this same pounds of removal with whole fluid would
require hauling 8 bbl of fluid. This would represent an 8 to 1 savings in hauling cost and disposal
cost.
The term closed-loop system, when only mechanical equipment is employed to remove the solids,
is more often than not a misnomer. That is, there is a limit on how long the operation of the fluid
system can go before fluid has to be displaced due to solids build up. The fact is, mechanical
equipment screens, centrifuges, etc. cannot economically remove solids that are in the colloidal
size range. If the closed-loop system is rated at 85% solids removal efficiency, then the other 15%
of the solids will have to be removed by displacing whole fluid. Not “opening up” the loop to
remove these excess solids is a common operational problem and will result in a fluid system that
has flow properties and fluid loss that are hard to control. This in turn causes chemical additions
above normal to counteract the excess of colloidal solids and the “loop” will ultimately have to be
“opened” to discard the excess solids.
Figures 10-9 and 10-10 depict the arrangement of mechanical solids removal equipment on a
closed-loop system for unweighted and weighted fluid systems respectively. The addition of the
dewatering system will make the closed-loop complete and allow it to truly reflect the name
“closed-loop system.” This is achieved by removing the excess
solids that remain in the fluid after
the mechanical processing.
Figure 10 - 9 Closed Loop Solids System – Unweighted Fluid
BAKER HUGHES DRILLING FLUIDS
REVISION 2006 10-19
REFERENCE MANUAL