Drilling Fluid Contamination: Cement

Drilling Fluid Contamination: Cement

Cement contamination occurs in every well drilled. It is contamination from calcium hydroxide which can result in increased pH, severe thickening and increased fluid loss of bentonite based mud…

Drilling Fluid Contamination: Carbonate/ Bicarbonate

One of the most unrecognised types of contamination is that due to Carbonate and Bicarbonate ions. Usually such contamination is gradual, resulting in increased gel strengths and yield point. It is…

Drilling Fluid Contamination: Calcium Sulphate (Anhydrite)

Contamination with Calcium Sulphate (Anhydrite) will result in flocculation of bentonite muds resulting in an increase in yield point, gel strengths and fluid loss.

Polymer muds are relatively…

Drilling Fluid Contamination: Salt

If salt enters a bentonite based mud, the clay platelets will flocculate resulting in gellation and increasedfluid loss (>10ml).

Polymer systems are tolerant to salt contamination. However, the…

Drilling Fluid Contamination: Hydrogen Sulphide (H2S)

H2S will have no adverse effects on the mud. However, the gas is highly poisonous and corrosive.

Sources of H2S

The gas is sometimes associated with formation fluids. (Add Biocide)



Barytes sag - treatment, prevention and causes

Generally, barytes sag is linked to a rapid change in mud properties, for operational reasons: Increase mw because of kick, reduce mw because of diff sticking pb, thinning mud at TD for the cement…

Summary Treatment of Mud Contaminants





Gypsum or Anhydrite

Calcium (Ca ++)

Soda ash if pH okay
Sodium bicarbonate if pH too high


Drilling Fluid Contamination

Contamination is a steady process while drilling, as drilled solids are continually entering the mud. While much of the drilled solids are inert, there are certain materials which can cause severe…

Drilling Fluid Contamination: Hardness

High levels of hardness will result in flocculation of bentonite with associated severe increases in viscosity. Subsequently, as the cation exchange process continues, the clay particles will…