BAKER HUGHES - Drilling Fluids Reference Manual

MECHANICAL SOLIDS CONTROL
Figure 10 - 2 Drilling Fluid Required if Discard Stream From All Solids Processing
Equipment Averages 30% by Volume Solids
The Methylene Blue Test (MBT) is used to determine the Cation Exchange Capacity (CEC) of
fresh water-base drilling fluid. The test measures the concentration of all active clays present in the
drilling fluid. Correcting the test results for commercial bentonite concentration allows the
concentration of all other clays to be estimated. Using the MBT test allows the concentration of
drilled solids to be estimated and the drilling fluid treated/processed accordingly to achieve a
predetermined drilled solids concentration. Efforts to reduce the drill solids concentration to lower
levels can result in unnecessary drilling fluid maintenance expense.
Oil or synthetic-based systems, along with certain polymer systems, because of their inherently
inhibitive nature, do not experience the same low gravity solids problems particular to fresh waterbase
drilling fluids.
The API Recommended Practices 13C contains a field method for evaluating the total efficiency of
the drilling fluid processing system in water-based fluids. This procedure depends upon accurate
dilution volume information. The API procedure uses the dilution volume over a given interval to
compute a dilution factor, DF, which is the volume ratio of actual mud dilution required to
maintain a desired solids concentration with no solids removal equipment. The dilution factor is
used to determine the total solids removal efficiency of the system. The API procedure is as
follows:
1. Over a desired interval length, obtain accurate water additions and retort data.
2. From the retort data, calculate:
a. The average drilled solids concentration in the mud, ks.
b. The average water fraction of the mud, kw.
BAKER HUGHES DRILLING FLUIDS
REVISION 2006 10-4
REFERENCE MANUAL