BAKER HUGHES - Drilling Fluids Reference Manual

Baker Hughes Drilling Fluids
Table 4-1
Comparisons of the Alkalinity Methods
P f /M f Method
The P f /M f titrations were historically the first method used to calculate carbonate concentrations.
As stated above it tends to be inaccurate because of the buffering of organic acids and dark
colored filtrates which make determination of endpoints difficult. Some of the inaccuracy of the
Mf endpoint can be eliminated by titrating using a properly calibrated pH meter but this will not
eliminate the effects of the buffering agents in the mud.
The calculations for using the P f /M f values to determine carbonate and bicarbonate concentrations
are shown in Table 4-2.
Table 4-2
P f /M f Alkalinity Ion Concentrations, mg/L
P1 – P2 Method for Hydroxyl/Carbonate/Bicarbonate Determination.
This carbonate determination method is based on filtrate alkalinity. Two values are determined
and designated P1 and P2. P1 is determined by using 1 ml of filtrate mixed with 14 ml of
deionized water plus 2 ml of 0.1N sodium hydroxide in a titrating dish. The pH of the mixture
should be greater than 11.4. If not then another 2 ml of 0.1 N sodium hydroxide is added. Now 2
ml of barium chloride is added to the titrating dish and then 2 to 4 drops of phenolphthalein. This
mixture is then titrated with 0.02N sulfuric acid to a pH of 8.3 or the Pf endpoint. The number of
mls required to reach this end point is recorded as the P1 value. To obtain P2, repeat the
procedure but with no filtrate. Once P1 and P2 values have been obtained calculate the values of
carbonates with the equations below.
Baker Hughes Drilling Fluids
Reference Manual
Revised 2006 4-9