Investigating the Effects of Contaminants on the Rheological Properties of Water-Based Mud

Abstract

For any drilling operation to be termed successful, care must be taken during
the selection and application of the drilling fluid which are key factors that
should be considered. Any actions contrary to carefully selection and
application of drilling fluids could have very dire consequences. Based on the
experiment work done on water base mud system to ascertain the effect of
contaminants (salt, silica sand, cement and carbonate) on the rheological
properties and performance of the mud, it shows that the presence of a
contaminant on the drilling mud either reduces or increases the rheological
properties of the mud system and in turn affects the rate of penetration, it
performance and also poses serious drilling problems. It was observed that
the presence of Sodium salt in the mud system increased the fluid loss into the
formation. It was further observed that while Apparent Viscosity, Gel
Strength increases as the mass increase from 1g to 5g, the pH and Plastic
Viscosity almost did not change. The Yield point increases little. With Cement
as contaminant, it shows all rheological properties of the mud increased
markedly, as the quantity of the cement used is increased from 1g to 5g and
the pH does not change. Silica contamination has not showed any marked
effect on the nature of the drilling mud. In fact, the more the amount of the
contaminant (Silica) is added, the closer it properties are to the blank sample
that do not have contaminants. The carbonate effect is largely on the Gel
strength which decreases as the amount of added carbonate increases. The
pH has no charges, which also means carbonate keeps the mud in it alkaline
state, as it was with cement.