Category Archives: Drilling Fluids

Alkalinity Excess Lime (Oil Based Mud Properties)

By | |
Leave a comment

For most of oil based mud, lime (Ca(OH)2) is used in the system in order to perform a chemical reaction with fatty acid emulsifiers. Typically, 3 to 5 lb/bbl of lime is added in the drilling mud so that there is enough hydroxide (OH-1) ions to keep the emulsion stability in  good shape.
Moreover, lime (Ca(OH)2) will control acid gases such as H2S and CO2. The following chemical equations demonstrate how lime reacts with H2S and CO2, respectively.

Ca(OH)2 + H2S -> CaS + 2(H2O)
Ca(OH)2 + CO2 -> CaCO3 + H2O

If drilling into zones where CO2 or H2S exists, the amount of excess lime should be increased to around 5 to 10 lb./bbl., because some lime is used for emulsion stability and others react with acid gases to maintain the mud’s properties.

What’s more, when the well is drilled into formations containing H2S, the excess lime must be kept constantly at 5 to 10 lb/bbl all the time. Do not try to reduce the amount of excess lime because the chemical reaction between H2S and lime is reversible. Therefore, if the level of excess lime is not maintained, the H2S gas can be released at the surface from the reversible chemical process.

References

Andy Philips, 2012. So You Want to be a Mud Engineer: An Introduction to Drilling Fluids Technology. Edition. CreateSpace Independent Publishing Platform.

Ryen Caenn, 2011. Composition and Properties of Drilling and Completion Fluids, Sixth Edition. 6 Edition. Gulf Professional Publishing.

Functions and Importances of Electrical Stability of Oil Based Mud

By | |
3 Comments

The Electrical Stability (ES) is one of the vital properties for oil based mud. It shows the voltage of the current flowing in the mud. The ES number represents the mud emulsion stability. The more ES is; the more the emulsion stability is.

 

Oil based fluid is a non-conductive material. Therefore, the base fluid will not transfer any current. Only the water phase in the mud will conduct the electricity. If the mud has good emulsion, you will have high ES figures. On the other hand, if the emulsion of the mud is bad, you will have low ES value.

 

The Electrical Stability (ES) is obtained from an electrical stability tester kit (see the image below).

Electrical Stability Meter

Electrical Stability Meter

Continue reading →

Total Hardness and Chloride Content in Water Based Mud

By | |
Leave a comment

“Total Hardness” or “Water Hardness” is a measurement of calcium (Ca2+) and magnesium (Mg 2+) ions in water base mud. The total of both soluble ions of calcium (Ca2+) and magnesium (Mg 2+) is given by titration with standard Vesenate solution.

Total-Hardness-and-Cl-content-and-Methylene-Blue-Test

What will be happening if you have a lot of total hardness in your drilling mud?

  • Bad mud cake (thick and mushy)
  • High fluid loss
  • Flocculation of clay content
  • Less polymer effectiveness
  • Ineffective chemical treatment

For most of the water base mud, the acceptable value of total hardness must be below 300 mg/L. If the lime drilling mud is used, it is acceptable to have a higher valu,e but is should be kept below 400 mg/L. Continue reading →

Pm, Pf and Mf of Drilling Mud (Water based mud)

By | |
3 Comments

Pm, Pf and Mf are values indicating the alkalinity of drilling mud and the following is meaning of each value.

Pm

Pm stands for “phenolphthalein end point of the mud” and it indicates quantities of Potassium Hydroxide (KOH), caustic soda, cement, etc., in the water base mud.  The Pm refers to the amount of acid required to reduce the pH of mud to 8.3. The Pm test includes the effect of both dissolved and non-dissolved bases and salts in drilling fluid.  Especially in lime mud, Pm is used to determine the ratio of insoluble lime to soluble lime in the filtrate.

Pf

Pf stands for the phenolphthalein alkalinity of the mud filtrate. Pf is different from the Pm because it tests the affect of only dissolved bases and salts.  However, Pm includes the effect of both dissolved and non-dissolved bases and salts in drilling mud. Continue reading →

pH in Drilling Mud (Water Based Mud)

By | |
Leave a comment

pH is a value representing the hydrogen ion concentration in liquid and it is used to indicate acidity or alkalinity of drilling mud. The pH is presented in a numerical value (0-14), which means an inverse measurement of hydrogen concentration in the fluid.

The pH formula is listed below;

pH = -log10[H]

Where: H is the hydrogen ion concentration in mol.

According to the pH formula, the more hydrogen atoms present, the more acidity of substance is but the pH valve decreases. Generally speaking, a pH of 7 means neutral. Fluids with a pH above 7 are considered as being alkaline. On the other hand, the fluids with pH below 7 are defined as being acidic.

In the drilling mud, there are three main chemical components involved in Alkalinity of drilling fluid, which are bicarbonate ions (HCO3–), hydroxyl ions (OH–), and carbonate ions (CO3-2). The Alkalinity means ions that will reduce the acidity. Continue reading →