Acidity is one measure of alkalinity that is indicated by the pH. However, the nature and amount of other ions such as Carbonates or Bicarbonates can also effect mud filtrates alkalinity.
For fresh water mud systems, these ions can be indicative of the rheological stability of such mud systems.
Concentrations of either ion can result in high, low shear rate viscosity (Yield Point) and high, progressive Gel Strengths.
•Three methods can be employed for the determination of Carbonate and Bicarbonate concentration. The very common Pf / Mf method is restricted to mud systems having a low organic content, whereas the P1 / P2 method or Garret Gas Train may be used for better, more quantitative method, especially in the systems with high organic content. Pf / Mf Method test procedures
•Using a 1 ml pipette, measure 1 ml of filtrate into a white titration dish. Dilute with distilled water.
•Add 2-3 drops of Phenolphthalein Indicator.
•if no color change occurs, then the Pf = 0; continue to step 4
•if a pink or red color develops, the Pf > 0; continue to step 3 •Using a pipette, add N/50 Sulfuric Acid continuously while swirling or stirring until the sample changes from pink to colorless (or original filtrate tint).
•The number of ml of N/50 Sulfuric Acid to reach this point is recorded as the Pf value.
•To the sample, which has been titrated to the Pf end point, add 2-3 drops of BromoCreosol indicator solution to obtain a light blue color. Continue titrating with swirling (or stirring) until the color changes from light blue to apple green (pH 4.0-4.5).
•This end point is recorded as the Mf end point.
ALKALINITY OF THE MUD (Pm
•This test measures the alkalinity of the whole mud. When used in conjunction with the filtrate alkalinity determination, the amount of excess Lime present in the mud can be determined.
Test Procedure
•Measure 1 ml of a freshly stirred sample of mud into a titration dish using a syringe.
•Dilute the mud in the dish with about 50 ml of distilled water.
•Add 4-5 drops of Phenolphthalein indicator solution.
•If the sample does not change color, record the Pm as 0.
•If the sample turns pink, titrate rapidly with N/50 Sulfuric Acid until the pink color disappears.
Calculations
•Report the alkalinity of the mud, Pm as the number of ml of N/50 Sulfuric Acid added until the pink color disappears.
•Note: If the mud sample is deeply colored and the color change is hard to see, use 0.5 ml of mud, and report the Pm as the volume of Sulfuric Acid added X 2.0. If N/10 (0.1N) Sulfuric Acid is used, the Pm is reported as the volume of acid added to 1 ml of mud X 5.0.
•This test measures the alkalinity of the whole mud. When used in conjunction with the filtrate alkalinity determination, the amount of excess Lime present in the mud can be determined.
Test Procedure
•Measure 1 ml of a freshly stirred sample of mud into a titration dish using a syringe.
•Dilute the mud in the dish with about 50 ml of distilled water.
•Add 4-5 drops of Phenolphthalein indicator solution.
•If the sample does not change color, record the Pm as 0.
•If the sample turns pink, titrate rapidly with N/50 Sulfuric Acid until the pink color disappears.
Calculations
•Report the alkalinity of the mud, Pm as the number of ml of N/50 Sulfuric Acid added until the pink color disappears.
•Note: If the mud sample is deeply colored and the color change is hard to see, use 0.5 ml of mud, and report the Pm as the volume of Sulfuric Acid added X 2.0. If N/10 (0.1N) Sulfuric Acid is used, the Pm is reported as the volume of acid added to 1 ml of mud X 5.0.
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