pH in Drilling Mud (Water Based Mud)

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.

In order to get accurate measurements for the pH, using a pH meter instead of using a pH paper is recommended because it will give more accurate pH figures. Additionally, pH meters must be calibrated frequently.

ph meter

Figure 1  – pH meter

 

Figure 2 - pH paper

Figure 2 – pH paper

Cause of a decrease in pH of drilling Mud

There are many factors that can cause reduction in pH of drilling mud as listed below;

Water contamination – The water contamination or water influx will decrease pH in the drilling fluid because water is neutral.

Carbonate or Bicarbonate – With these two chemical molecules, the pH of drilling mud will be reduced.

Acid gases as Carbon dioxide (CO2) and Sulphur Dioxide (H2S) – If there are acid gases mixing in the system, the pH will decrease.  Additionally, acid gas has bad effect on mud properties. The rheology of the mud as PV, YP, and gel strength will increase, but Pm and Pf will decrease due to loss of pH.

Anhydrite – Chemical components of Anhydrite will neutralize hydrogen ions in the mud so pH of drilling mud will drop. It is important to increase mud pH while drilling Anhydrite formation.

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.

Related Post

Mud Filter Cake Mud filter cake is a layer formed by solid particles in drilling mud against porous zones due to differential pressure between hydrostatic pressure an...
Viscosity of Drilling Mud Viscosity describes a substance's resistance to flow. High-viscosity drilling mud is typically described as "thick," while low-viscosity mud is charac...
Determine Quantity of Material Used in Mixing a Si... This is a simple example to demonstrate how to determine quantity of material required in a simple mixing system. Let's learn from the example below. ...
Types of Flow and Rheology Models of Drilling Mud When you learn about drilling mud, the rheological models are essential knowledge. The rheological models are critical for a drilling fluid study beca...
Share the joy
  • 164
  •  
  •  
  •  
  •  
  •  
  •  
  •  
  •  
    164
    Shares
Tagged , , , . Bookmark the permalink.

About DrillingFormulas.Com

Working in the oil field and loving to share knowledge.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.