The following table presents the main contaminants and the chemical treatment to be used.   CONTAMINANT CONTAMINANT ION TREATMENT CHEMICAL CONCENTRATION PER 100 ppm CONTAMINANT Gypsum or Anhydrite Calcium (Ca ++) Soda ash if pH okay Sodium bicarbonate if pH too high 0.1 lb/bbl 0.15 lb/bbl Cement Calcium (Ca ++) Hydroxide (OH) Sodium bicarbonate 0.15 … Summary Treatment of Mud Contaminants

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 insensitive to this type of contamination, unless significant quantities of drilled clay solids are present. Sources of Contamination This type of contamination can occur whilst drilling Anhydrite. … Drilling Fluid Contamination: Calcium Sulphate (Anhydrite)

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 chemical and physical problems.  Contaminants tend to become apparent more quickly with lightly treated muds rather than with more highly inhibited varieties. Any contamination … Drilling Fluid Contamination

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) Diagnosis Gas liberated at surface will be detected by gas sensors. Soluble sulphides in the mud are detected by use of the Garret Gas Train. … Drilling Fluid Contamination: Hydrogen Sulphide (H2S)

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 aggregate and the result will be a low viscosity fluid. The main effect of hardness on polymer fluids is precipitation of polymers at high pH (>11) in which … Drilling Fluid Contamination: Hardness

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 salt acts to reduce the yield of most polymers (not Starch), and in practice, high salt concentrations will require a higher concentration of polymer for the same … Drilling Fluid Contamination: Salt

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 systems (flocculation of the bentonite clay). The severity of the problem will depend on the level of pre-treatment and thinner concentration in the mud. In a … Drilling Fluid Contamination: Cement

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 often incorrectly diagnosed as increased solids but, in this case, application of costly thinners have little, or no effect. Sources of Carbonates C02 from drilled … Drilling Fluid Contamination: Carbonate/ Bicarbonate

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 job, etc. – POBM systems are usually very thin and often run at low gels 5/20 and low “low end” rheology. … Barytes sag – treatment, prevention and causes